initial commit with overhauled / rebranded project

.github/FUNDING.yml

@@ -0,0 +1 @@
+custom: https://grapheneos.org/donate

.gitignore

@@ -0,0 +1,7 @@
+*.iml
+.gradle
+local.properties
+build/
+signing.properties
+*.jks
+/.idea

LICENSE

@@ -0,0 +1,19 @@
+Copyright (c) 2019 Daniel Micay
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

PDFJS_LICENSE

@@ -0,0 +1,177 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
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+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
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+
+      (d) If the Work includes a "NOTICE" text file as part of its
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+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS

app/.gitignore

@@ -0,0 +1 @@
+/build

app/build.gradle

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+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 28
+    buildToolsVersion "29.0.0"
+    defaultConfig {
+        applicationId "org.grapheneos.pdfviewer"
+        minSdkVersion 24
+        targetSdkVersion 28
+        versionCode 1
+        versionName versionCode.toString()
+        resConfigs "en"
+    }
+
+    signingConfigs {
+        release
+    }
+    buildTypes {
+        debug {
+            applicationIdSuffix ".debug"
+        }
+        release {
+            minifyEnabled true
+            shrinkResources true
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+            signingConfig signingConfigs.release
+        }
+    }
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+}
+
+dependencies {
+    implementation fileTree(include: ['*.jar'], dir: 'libs')
+    implementation 'androidx.appcompat:appcompat:1.0.2'
+}
+
+def props = new Properties()
+def propFile = new File('signing.properties')
+
+if (propFile.canRead()) {
+    props.load(new FileInputStream(propFile))
+
+    if (props != null &&
+            props.containsKey('STORE_FILE')     &&
+            props.containsKey('STORE_PASSWORD') &&
+            props.containsKey('KEY_ALIAS')      &&
+            props.containsKey('KEY_PASSWORD')) {
+        android.signingConfigs.release.storeFile = rootProject.file(props['STORE_FILE'])
+        android.signingConfigs.release.storePassword = props['STORE_PASSWORD']
+        android.signingConfigs.release.keyAlias = props['KEY_ALIAS']
+        android.signingConfigs.release.keyPassword = props['KEY_PASSWORD']
+    } else {
+        println 'signing.properties found but some entries are missing'
+        android.buildTypes.release.signingConfig = null
+    }
+} else {
+    println 'signing.properties not found'
+    android.buildTypes.release.signingConfig = null
+}

app/lint.xml

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+<lint>
+    <!-- full backups are desired -->
+    <issue id="AllowBackup">
+        <ignore path="src/main/AndroidManifest.xml"/>
+    </issue>
+
+    <!-- Google app indexing doesn't make any sense for this app -->
+    <issue id="AppLinkUrlError">
+        <ignore path="src/main/AndroidManifest.xml"/>
+    </issue>
+
+    <!-- targetSandboxVersion unused with API level < 26 -->
+    <issue id="UnusedAttribute">
+        <ignore path="src/main/AndroidManifest.xml"/>
+    </issue>
+</lint>

app/proguard-rules.pro

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+-keepclassmembers class * {
+    @android.webkit.JavascriptInterface <methods>;
+}

app/src/main/AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+        package="org.grapheneos.pdfviewer"
+        android:targetSandboxVersion="2">
+    <application android:icon="@mipmap/ic_launcher"
+            android:roundIcon="@mipmap/ic_launcher_round"
+            android:label="@string/app_name"
+            android:theme="@style/AppTheme"
+            android:allowBackup="true">
+        <activity android:name=".PdfViewer"
+                android:label="@string/app_name">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:mimeType="application/pdf" />
+            </intent-filter>
+        </activity>
+
+        <meta-data android:name="android.webkit.WebView.MetricsOptOut"
+                android:value="true" />
+        <meta-data android:name="android.webkit.WebView.EnableSafeBrowsing"
+                android:value="false" />
+    </application>
+</manifest>

app/src/main/assets/viewer.css

@@ -0,0 +1,66 @@
+body, canvas {
+    padding: 0;
+    margin: 0;
+}
+
+.textLayer {
+    position: absolute;
+    left: 0;
+    top: 0;
+    right: 0;
+    bottom: 0;
+    overflow: hidden;
+    opacity: 0.2;
+    line-height: 1.0;
+}
+
+.textLayer > div {
+    color: transparent;
+    position: absolute;
+    white-space: pre;
+    cursor: text;
+    transform-origin: 0% 0%;
+}
+
+.textLayer .highlight {
+    margin: -1px;
+    padding: 1px;
+
+    background-color: rgb(180, 0, 170);
+    border-radius: 4px;
+}
+
+.textLayer .highlight.begin {
+    border-radius: 4px 0px 0px 4px;
+}
+
+.textLayer .highlight.end {
+    border-radius: 0px 4px 4px 0px;
+}
+
+.textLayer .highlight.middle {
+    border-radius: 0px;
+}
+
+.textLayer .highlight.selected {
+    background-color: rgb(0, 100, 0);
+}
+
+.textLayer ::selection { background: rgb(0,0,255); }
+.textLayer ::-moz-selection { background: rgb(0,0,255); }
+
+.textLayer .endOfContent {
+    display: block;
+    position: absolute;
+    left: 0px;
+    top: 100%;
+    right: 0px;
+    bottom: 0px;
+    z-index: -1;
+    cursor: default;
+    user-select: none;
+}
+
+.textLayer .endOfContent.active {
+    top: 0px;
+}

app/src/main/assets/viewer.html

@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <meta name="viewport" content="width=device-width, user-scalable=no" />
+        <title>PDF</title>
+        <link rel="stylesheet" href="viewer.css" />
+        <script src="pdf.js"></script>
+    </head>
+    <body>
+        <canvas id="content"></canvas>
+        <div id="text" class="textLayer"></div>
+        <script src="viewer.js"></script>
+    </body>
+</html>

app/src/main/assets/viewer.js

@@ -0,0 +1,193 @@
+"use strict";
+
+let pdfDoc = null;
+let pageRendering = false;
+let renderPending = false;
+let renderPendingLazy = false;
+const canvas = document.getElementById('content');
+let zoomLevel = 100;
+let textLayerDiv = document.getElementById("text");
+const zoomLevels = [50, 75, 100, 125, 150];
+let task = null;
+
+let newPageNumber = 0;
+let newZoomLevel = 0;
+let useRender;
+
+const cache = [];
+const maxCached = 6;
+
+function maybeRenderNextPage() {
+    if (renderPending) {
+        pageRendering = false;
+        renderPending = false;
+        renderPage(channel.getPage(), renderPendingLazy, false);
+        return true;
+    }
+    return false;
+}
+
+function handleRenderingError(error) {
+    console.log("rendering error: " + error);
+
+    pageRendering = false;
+    maybeRenderNextPage();
+}
+
+function doPrerender(pageNumber, prerenderTrigger) {
+    if (useRender) {
+        if (pageNumber + 1 <= pdfDoc.numPages) {
+            renderPage(pageNumber + 1, false, true, pageNumber);
+        } else if (pageNumber - 1 > 0) {
+            renderPage(pageNumber - 1, false, true, pageNumber);
+        }
+    } else if (pageNumber == prerenderTrigger + 1) {
+        if (prerenderTrigger - 1 > 0) {
+            renderPage(prerenderTrigger - 1, false, true, prerenderTrigger);
+        }
+    }
+}
+
+function display(newCanvas) {
+    canvas.height = newCanvas.height;
+    canvas.width = newCanvas.width;
+    canvas.style.height = newCanvas.style.height;
+    canvas.style.width = newCanvas.style.width;
+    canvas.getContext("2d", { alpha: false }).drawImage(newCanvas, 0, 0);
+    scrollTo(0, 0);
+}
+
+function renderPage(pageNumber, lazy, prerender, prerenderTrigger=0) {
+    pageRendering = true;
+    useRender = !prerender;
+
+    newPageNumber = pageNumber;
+    newZoomLevel = zoomLevels[channel.getZoomLevel()];
+    console.log("page: " + pageNumber + ", zoom: " + newZoomLevel + ", prerender: " + prerender);
+    for (let i = 0; i < cache.length; i++) {
+        const cached = cache[i];
+        if (cached.pageNumber === pageNumber && cached.zoomLevel === newZoomLevel) {
+            if (useRender) {
+                cache.splice(i, 1);
+                cache.push(cached);
+
+                display(cached.canvas);
+
+                textLayerDiv.replaceWith(cached.textLayerDiv);
+                textLayerDiv = cached.textLayerDiv;
+            }
+
+            pageRendering = false;
+            doPrerender(pageNumber, prerenderTrigger);
+            return;
+        }
+    }
+
+    pdfDoc.getPage(pageNumber).then(function(page) {
+        if (maybeRenderNextPage()) {
+            return;
+        }
+
+        const newCanvas = document.createElement("canvas");
+        const viewport = page.getViewport(newZoomLevel / 100)
+        const ratio = window.devicePixelRatio;
+        newCanvas.height = viewport.height * ratio;
+        newCanvas.width = viewport.width * ratio;
+        newCanvas.style.height = viewport.height + "px";
+        newCanvas.style.width = viewport.width + "px";
+        const newContext = newCanvas.getContext("2d", { alpha: false });
+        newContext.scale(ratio, ratio);
+
+        if (useRender) {
+            if (newZoomLevel != zoomLevel) {
+                canvas.style.height = viewport.height + "px";
+                canvas.style.width = viewport.width + "px";
+            }
+            zoomLevel = newZoomLevel;
+        }
+
+        task = page.render({
+            canvasContext: newContext,
+            viewport: viewport
+        });
+
+        task.then(function() {
+            task = null;
+
+            let rendered = false;
+            function render() {
+                if (!useRender || rendered) {
+                    return;
+                }
+                display(newCanvas);
+                rendered = true;
+            }
+            render();
+
+            const textLayerFrag = document.createDocumentFragment();
+            task = PDFJS.renderTextLayer({
+                textContentStream: page.streamTextContent(),
+                container: textLayerFrag,
+                viewport: viewport
+            });
+            task.promise.then(function() {
+                task = null;
+
+                render();
+
+                const newTextLayerDiv = textLayerDiv.cloneNode();
+                newTextLayerDiv.style.height = newCanvas.style.height;
+                newTextLayerDiv.style.width = newCanvas.style.width;
+                if (useRender) {
+                    textLayerDiv.replaceWith(newTextLayerDiv);
+                    textLayerDiv = newTextLayerDiv;
+                }
+                newTextLayerDiv.appendChild(textLayerFrag);
+
+                if (cache.length === maxCached) {
+                    cache.shift()
+                }
+                cache.push({
+                    pageNumber: pageNumber,
+                    zoomLevel: newZoomLevel,
+                    canvas: newCanvas,
+                    textLayerDiv: newTextLayerDiv
+                });
+
+                pageRendering = false;
+                doPrerender(pageNumber, prerenderTrigger);
+            }).catch(handleRenderingError);
+        }).catch(handleRenderingError);
+    });
+}
+
+function onRenderPage(lazy) {
+    if (pageRendering) {
+        if (newPageNumber === channel.getPage() && newZoomLevel === zoomLevels[channel.getZoomLevel()]) {
+            useRender = true;
+            return;
+        }
+
+        renderPending = true;
+        renderPendingLazy = lazy;
+        if (task !== null) {
+            task.cancel();
+            task = null;
+        }
+    } else {
+        renderPage(channel.getPage(), lazy, false);
+    }
+}
+
+PDFJS.getDocument("https://localhost/placeholder.pdf").then(function(newDoc) {
+    pdfDoc = newDoc;
+    channel.setNumPages(pdfDoc.numPages);
+    pdfDoc.getMetadata().then(function(data) {
+        channel.setDocumentProperties(JSON.stringify(data.info));
+    }).catch(function(error) {
+        console.log("getMetadata error: " + error);
+    });
+    renderPage(channel.getPage(), false, false);
+}).catch(function(error) {
+    console.log("getDocument error: " + error);
+});

app/src/main/java/org/grapheneos/pdfviewer/PdfViewer.java

@@ -0,0 +1,442 @@
+package org.grapheneos.pdfviewer;
+
+import android.annotation.SuppressLint;
+import android.app.Activity;
+import android.content.Intent;
+import android.content.res.ColorStateList;
+import android.graphics.Color;
+import android.net.Uri;
+import android.os.Bundle;
+import android.util.Log;
+import android.view.Gravity;
+import android.view.Menu;
+import android.view.MenuInflater;
+import android.view.MenuItem;
+import android.webkit.CookieManager;
+import android.webkit.JavascriptInterface;
+import android.webkit.WebResourceRequest;
+import android.webkit.WebResourceResponse;
+import android.webkit.WebSettings;
+import android.webkit.WebView;
+import android.webkit.WebViewClient;
+import android.widget.TextView;
+import android.widget.Toast;
+
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.loader.app.LoaderManager;
+import androidx.loader.content.Loader;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+
+import org.grapheneos.pdfviewer.fragment.DocumentPropertiesFragment;
+import org.grapheneos.pdfviewer.fragment.JumpToPageFragment;
+import org.grapheneos.pdfviewer.loader.DocumentPropertiesLoader;
+
+public class PdfViewer extends AppCompatActivity implements LoaderManager.LoaderCallbacks<List<CharSequence>> {
+    public static final String TAG = "PdfViewer";
+
+    private static final String STATE_URI = "uri";
+    private static final String STATE_PAGE = "page";
+    private static final String STATE_ZOOM_LEVEL = "zoomLevel";
+    private static final String KEY_PROPERTIES = "properties";
+
+    private static final String CONTENT_SECURITY_POLICY =
+        "default-src 'none'; " +
+        "form-action 'none'; " +
+        "connect-src https://localhost/placeholder.pdf; " +
+        "img-src blob: 'self'; " +
+        "script-src 'self'; " +
+        "style-src 'self'; " +
+        "frame-ancestors 'none'; " +
+        "base-uri 'none'";
+
+    private static final String FEATURE_POLICY =
+        "accelerometer 'none'; " +
+        "ambient-light-sensor 'none'; " +
+        "autoplay 'none'; " +
+        "camera 'none'; " +
+        "encrypted-media 'none'; " +
+        "fullscreen 'none'; " +
+        "geolocation 'none'; " +
+        "gyroscope 'none'; " +
+        "magnetometer 'none'; " +
+        "microphone 'none'; " +
+        "midi 'none'; " +
+        "payment 'none'; " +
+        "picture-in-picture 'none'; " +
+        "speaker 'none'; " +
+        "sync-xhr 'none'; " +
+        "usb 'none'; " +
+        "vr 'none'";
+
+    private static final int MIN_ZOOM_LEVEL = 0;
+    private static final int MAX_ZOOM_LEVEL = 4;
+    private static final int ALPHA_LOW = 130;
+    private static final int ALPHA_HIGH = 255;
+    private static final int ACTION_OPEN_DOCUMENT_REQUEST_CODE = 1;
+    private static final int STATE_LOADED = 1;
+    private static final int STATE_END = 2;
+    private static final int PADDING = 10;
+
+    private Uri mUri;
+    public int mPage;
+    public int mNumPages;
+    private int mZoomLevel = 2;
+    private int mDocumentState;
+    private List<CharSequence> mDocumentProperties;
+    private InputStream mInputStream;
+
+    private WebView mWebView;
+    private TextView mTextView;
+    private Toast mToast;
+
+    private class Channel {
+        @JavascriptInterface
+        public int getPage() {
+            return mPage;
+        }
+
+        @JavascriptInterface
+        public int getZoomLevel() {
+            return mZoomLevel;
+        }
+
+        @JavascriptInterface
+        public void setNumPages(int numPages) {
+            mNumPages = numPages;
+        }
+
+        @JavascriptInterface
+        public void setDocumentProperties(final String properties) {
+            if (mDocumentProperties != null) {
+                throw new SecurityException("mDocumentProperties not null");
+            }
+
+            final Bundle args = new Bundle();
+            args.putString(KEY_PROPERTIES, properties);
+            runOnUiThread(() -> {
+                LoaderManager.getInstance(PdfViewer.this).restartLoader(DocumentPropertiesLoader.ID, args, PdfViewer.this);
+            });
+        }
+    }
+
+    // Can be removed once minSdkVersion >= 26
+    @SuppressWarnings("deprecation")
+    private void disableSaveFormData(final WebSettings settings) {
+        settings.setSaveFormData(false);
+    }
+
+    @Override
+    @SuppressLint("SetJavaScriptEnabled")
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        setContentView(R.layout.webview);
+
+        mWebView = findViewById(R.id.webview);
+        final WebSettings settings = mWebView.getSettings();
+        settings.setAllowContentAccess(false);
+        settings.setAllowFileAccess(false);
+        settings.setCacheMode(WebSettings.LOAD_NO_CACHE);
+        settings.setJavaScriptEnabled(true);
+        disableSaveFormData(settings);
+
+        CookieManager.getInstance().setAcceptCookie(false);
+
+        mWebView.addJavascriptInterface(new Channel(), "channel");
+
+        mWebView.setWebViewClient(new WebViewClient() {
+            private WebResourceResponse fromAsset(final String mime, final String path) {
+                try {
+                    InputStream inputStream = getAssets().open(path.substring(1));
+                    return new WebResourceResponse(mime, null, inputStream);
+                } catch (IOException e) {
+                    return null;
+                }
+            }
+
+            @Override
+            public WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request) {
+                if (!"GET".equals(request.getMethod())) {
+                    return null;
+                }
+
+                final Uri url = request.getUrl();
+                if (!"localhost".equals(url.getHost())) {
+                    return null;
+                }
+
+                final String path = url.getPath();
+                Log.d(TAG, "path " + path);
+
+                if ("/placeholder.pdf".equals(path)) {
+                    return new WebResourceResponse("application/pdf", null, mInputStream);
+                }
+
+                if ("/viewer.html".equals(path)) {
+                    final WebResourceResponse response = fromAsset("text/html", path);
+                    HashMap<String, String> headers = new HashMap<String, String>();
+                    headers.put("Content-Security-Policy", CONTENT_SECURITY_POLICY);
+                    headers.put("Feature-Policy", FEATURE_POLICY);
+                    response.setResponseHeaders(headers);
+                    return response;
+                }
+
+                if ("/viewer.css".equals(path)) {
+                    return fromAsset("text/css", path);
+                }
+
+                if ("/viewer.js".equals(path)) {
+                    return fromAsset("application/javascript", path);
+                }
+
+                if ("/pdf.js".equals(path)) {
+                    return fromAsset("application/javascript", path);
+                }
+
+                if ("/pdf.worker.js".equals(path)) {
+                    return fromAsset("application/javascript", path);
+                }
+
+                return null;
+            }
+
+            @Override
+            public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
+                return true;
+            }
+
+            @Override
+            public void onPageFinished(WebView view, String url) {
+                mDocumentState = STATE_LOADED;
+                invalidateOptionsMenu();
+            }
+        });
+
+        mTextView = new TextView(this);
+        mTextView.setBackgroundColor(Color.DKGRAY);
+        mTextView.setTextColor(ColorStateList.valueOf(Color.WHITE));
+        mTextView.setTextSize(18);
+        mTextView.setPadding(PADDING, 0, PADDING, 0);
+
+        // If loaders are not being initialized in onCreate(), the result will not be delivered
+        // after orientation change (See FragmentHostCallback), thus initialize the
+        // loader manager impl so that the result will be delivered.
+        LoaderManager.getInstance(this);
+
+        final Intent intent = getIntent();
+        if (Intent.ACTION_VIEW.equals(intent.getAction())) {
+            if (!"application/pdf".equals(intent.getType())) {
+                Log.e(TAG, "invalid mime type");
+                finish();
+                return;
+            }
+            mUri = intent.getData();
+            mPage = 1;
+        }
+
+        if (savedInstanceState != null) {
+            mUri = savedInstanceState.getParcelable(STATE_URI);
+            mPage = savedInstanceState.getInt(STATE_PAGE);
+            mZoomLevel = savedInstanceState.getInt(STATE_ZOOM_LEVEL);
+        }
+
+        if (mUri != null) {
+            loadPdf();
+        }
+    }
+
+    @Override
+    public Loader<List<CharSequence>> onCreateLoader(int id, Bundle args) {
+        return new DocumentPropertiesLoader(this, args.getString(KEY_PROPERTIES), mNumPages, mUri);
+    }
+
+    @Override
+    public void onLoadFinished(Loader<List<CharSequence>> loader, List<CharSequence> data) {
+        mDocumentProperties = data;
+        LoaderManager.getInstance(this).destroyLoader(DocumentPropertiesLoader.ID);
+    }
+
+    @Override
+    public void onLoaderReset(Loader<List<CharSequence>> loader) {
+        mDocumentProperties = null;
+    }
+
+    private void loadPdf() {
+        try {
+            if (mInputStream != null) {
+                mInputStream.close();
+            }
+            mInputStream = getContentResolver().openInputStream(mUri);
+        } catch (IOException e) {
+            return;
+        }
+        mWebView.loadUrl("https://localhost/viewer.html");
+    }
+
+    private void renderPage(final boolean lazy) {
+        mWebView.evaluateJavascript(lazy ? "onRenderPage(true)" : "onRenderPage(false)", null);
+    }
+
+    private void openDocument() {
+        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
+        intent.addCategory(Intent.CATEGORY_OPENABLE);
+        intent.setType("application/pdf");
+        startActivityForResult(intent, ACTION_OPEN_DOCUMENT_REQUEST_CODE);
+    }
+
+    private static void enableDisableMenuItem(MenuItem item, boolean enable) {
+        if (enable) {
+            if (!item.isEnabled()) {
+                item.setEnabled(true);
+                item.getIcon().setAlpha(ALPHA_HIGH);
+            }
+        } else if (item.isEnabled()) {
+            item.setEnabled(false);
+            item.getIcon().setAlpha(ALPHA_LOW);
+        }
+    }
+
+    public void onJumpToPageInDocument(int selected_page) {
+        if (selected_page >= 1 && selected_page <= mNumPages) {
+            mPage = selected_page;
+            renderPage(false);
+            showPageNumber();
+        }
+    }
+
+    @Override
+    public void onSaveInstanceState(Bundle savedInstanceState) {
+        super.onSaveInstanceState(savedInstanceState);
+        savedInstanceState.putParcelable(STATE_URI, mUri);
+        savedInstanceState.putInt(STATE_PAGE, mPage);
+        savedInstanceState.putInt(STATE_ZOOM_LEVEL, mZoomLevel);
+    }
+
+    @Override
+    protected void onActivityResult(int requestCode, int resultCode, Intent resultData) {
+        if (requestCode == ACTION_OPEN_DOCUMENT_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
+            if (resultData != null) {
+                mUri = resultData.getData();
+                mPage = 1;
+                mDocumentProperties = null;
+                loadPdf();
+                invalidateOptionsMenu();
+            }
+        }
+    }
+
+    private void showPageNumber() {
+        if (mToast != null) {
+            mToast.cancel();
+        }
+        mTextView.setText(String.format("%s/%s", mPage, mNumPages));
+        mToast = new Toast(getApplicationContext());
+        mToast.setGravity(Gravity.BOTTOM | Gravity.END, PADDING, PADDING);
+        mToast.setDuration(Toast.LENGTH_SHORT);
+        mToast.setView(mTextView);
+        mToast.show();
+    }
+
+    @Override
+    public boolean onCreateOptionsMenu(Menu menu) {
+        super.onCreateOptionsMenu(menu);
+        MenuInflater inflater = getMenuInflater();
+        inflater.inflate(R.menu.pdf_viewer, menu);
+        return true;
+    }
+
+    @Override
+    public boolean onPrepareOptionsMenu(Menu menu) {
+        final int ids[] = { R.id.action_zoom_in, R.id.action_zoom_out, R.id.action_jump_to_page,
+                R.id.action_next, R.id.action_previous, R.id.action_view_document_properties };
+        if (mDocumentState < STATE_LOADED) {
+            for (final int id : ids) {
+                final MenuItem item = menu.findItem(id);
+                if (item.isVisible()) {
+                    item.setVisible(false);
+                }
+            }
+        } else if (mDocumentState == STATE_LOADED) {
+            for (final int id : ids) {
+                final MenuItem item = menu.findItem(id);
+                if (!item.isVisible()) {
+                    item.setVisible(true);
+                }
+            }
+            mDocumentState = STATE_END;
+        }
+
+        switch (mZoomLevel) {
+            case MAX_ZOOM_LEVEL:
+                enableDisableMenuItem(menu.findItem(R.id.action_zoom_in), false);
+                return true;
+            case MIN_ZOOM_LEVEL:
+                enableDisableMenuItem(menu.findItem(R.id.action_zoom_out), false);
+                return true;
+            default:
+                enableDisableMenuItem(menu.findItem(R.id.action_zoom_in), true);
+                enableDisableMenuItem(menu.findItem(R.id.action_zoom_out), true);
+                return true;
+        }
+    }
+
+    @Override
+    public boolean onOptionsItemSelected(MenuItem item) {
+        switch (item.getItemId()) {
+            case R.id.action_previous:
+                if (mPage > 1) {
+                    mPage--;
+                    renderPage(false);
+                    showPageNumber();
+                }
+                return true;
+
+            case R.id.action_next:
+                if (mPage < mNumPages) {
+                    mPage++;
+                    renderPage(false);
+                    showPageNumber();
+                }
+                return true;
+
+            case R.id.action_open:
+                openDocument();
+                return super.onOptionsItemSelected(item);
+
+            case R.id.action_zoom_out:
+                if (mZoomLevel > 0) {
+                    mZoomLevel--;
+                    renderPage(true);
+                    invalidateOptionsMenu();
+                }
+                return true;
+
+            case R.id.action_zoom_in:
+                if (mZoomLevel < MAX_ZOOM_LEVEL) {
+                    mZoomLevel++;
+                    renderPage(true);
+                    invalidateOptionsMenu();
+                }
+                return true;
+
+            case R.id.action_view_document_properties:
+                DocumentPropertiesFragment
+                        .getInstance((ArrayList<CharSequence>) mDocumentProperties)
+                        .show(getSupportFragmentManager(), DocumentPropertiesFragment.TAG);
+                return true;
+
+            case R.id.action_jump_to_page:
+                new JumpToPageFragment()
+                    .show(getSupportFragmentManager(), JumpToPageFragment.TAG);
+                return true;
+
+            default:
+                return super.onOptionsItemSelected(item);
+        }
+    }
+}

app/src/main/java/org/grapheneos/pdfviewer/Utils.java

@@ -0,0 +1,196 @@
+package org.grapheneos.pdfviewer;
+
+import android.text.TextUtils;
+
+import java.math.RoundingMode;
+import java.text.DateFormat;
+import java.text.DecimalFormat;
+import java.text.ParseException;
+import java.util.Calendar;
+
+public class Utils {
+    public static String parseFileSize(long fileSize) {
+        final double kb = fileSize / 1000;
+
+        if (kb == 0) {
+            return fileSize + " Bytes";
+        }
+
+        final DecimalFormat format = new DecimalFormat("#.##");
+        format.setRoundingMode(RoundingMode.CEILING);
+
+        if (kb < 1000) {
+            return format.format(kb) + " kB (" + fileSize + " Bytes)";
+        }
+        return format.format(kb / 1000) + " MB (" + fileSize + " Bytes)";
+    }
+
+    // Parse date as per PDF spec (complies with PDF v1.4 to v1.7)
+    public static String parseDate(String date) throws ParseException {
+        int position = 0;
+
+        // D: prefix is optional for PDF < v1.7; required for PDF v1.7
+        if (!date.startsWith("D:")) {
+            date = "D:" + date;
+        }
+        if (date.length() < 6 || date.length() > 23) {
+            throw new ParseException("Invalid datetime length", position);
+        }
+
+        final Calendar calendar = Calendar.getInstance();
+        final int currentYear = calendar.get(Calendar.YEAR);
+        int year;
+
+        // Year is required
+        String field = date.substring(position += 2, 6);
+        if (!TextUtils.isDigitsOnly(field)) {
+            throw new ParseException("Invalid year", position);
+        }
+        year = Integer.valueOf(field);
+        if (year > currentYear) {
+            year = currentYear;
+        }
+
+        position += 4;
+
+        // Default value for month and day shall be 1 (calendar month starts at 0 in Java 7),
+        // all others default to 0
+        int month = 0;
+        int day = 1;
+        int hours = 0;
+        int minutes = 0;
+        int seconds = 0;
+
+        // All succeeding fields are optional, but each preceding field must be present
+        if (date.length() > 8) {
+            field = date.substring(position, 8);
+            if (!TextUtils.isDigitsOnly(field)) {
+                throw new ParseException("Invalid month", position);
+            }
+            month = Integer.valueOf(field) - 1;
+            if (month > 11) {
+                throw new ParseException("Invalid month", position);
+            }
+            position += 2;
+        }
+        if (date.length() > 10) {
+            field = date.substring(8, 10);
+            if (!TextUtils.isDigitsOnly(field)) {
+                throw new ParseException("Invalid day", position);
+            }
+            day = Integer.valueOf(field);
+            if (day > 31) {
+                throw new ParseException("Invalid day", position);
+            }
+            position += 2;
+        }
+        if (date.length() > 12) {
+            field = date.substring(10, 12);
+            if (!TextUtils.isDigitsOnly(field)) {
+                throw new ParseException("Invalid hours", position);
+            }
+            hours = Integer.valueOf(field);
+            if (hours > 23) {
+                throw new ParseException("Invalid hours", position);
+            }
+            position += 2;
+        }
+        if (date.length() > 14) {
+            field = date.substring(12, 14);
+            if (!TextUtils.isDigitsOnly(field)) {
+                throw new ParseException("Invalid minutes", position);
+            }
+            minutes = Integer.valueOf(field);
+            if (minutes > 59) {
+                throw new ParseException("Invalid minutes", position);
+            }
+            position += 2;
+        }
+        if (date.length() > 16) {
+            field = date.substring(14, 16);
+            if (!TextUtils.isDigitsOnly(field)) {
+                throw new ParseException("Invalid seconds", position);
+            }
+            seconds = Integer.valueOf(field);
+            if (seconds > 59) {
+                throw new ParseException("Invalid seconds", position);
+            }
+            position += 2;
+        }
+
+
+        if (date.length() > position) {
+            int offsetHours = 0;
+            int offsetMinutes = 0;
+
+            final char utRel = date.charAt(position);
+            if (utRel != '\u002D' && utRel != '\u002B' && utRel != '\u005A') {
+                throw new ParseException("Invalid UT relation", position);
+            }
+
+            position++;
+
+            if (date.length() > position + 2) {
+                field = date.substring(position, position + 2);
+                if (!TextUtils.isDigitsOnly(field)) {
+                    throw new ParseException("Invalid UTC offset hours", position);
+                }
+                offsetHours = Integer.parseInt(field);
+                final int offsetHoursMinutes = offsetHours * 100 + offsetMinutes;
+
+                // Validate UTC offset (UTC-12:00 to UTC+14:00)
+                if ((utRel == '\u002D' && offsetHoursMinutes > 1200) ||
+                        (utRel == '\u002B' && offsetHoursMinutes > 1400)) {
+                    throw new ParseException("Invalid UTC offset hours", position);
+                }
+
+                position += 2;
+
+                // Apostrophe shall succeed HH and precede mm
+                if (date.charAt(position) != '\'') {
+                    throw new ParseException("Expected apostrophe", position);
+                }
+
+                position++;
+
+                if (date.length() > position + 2) {
+                    field = date.substring(position, position + 2);
+                    if (!TextUtils.isDigitsOnly(field)) {
+                        throw new ParseException("Invalid UTC offset minutes", position);
+                    }
+                    offsetMinutes = Integer.parseInt(field);
+                    if (offsetMinutes > 59) {
+                        throw new ParseException("Invalid UTC offset minutes", position);
+                    }
+                    position += 2;
+                }
+
+                // Apostrophe shall succeed mm
+                if (date.charAt(position) != '\'') {
+                    throw new ParseException("Expected apostrophe", position);
+                }
+            }
+
+
+            switch (utRel) {
+                case '\u002D':
+                    hours -= offsetHours;
+                    minutes -= offsetMinutes;
+                    break;
+                case '\u002B':
+                    hours += offsetHours;
+                    minutes += offsetMinutes;
+                    break;
+                default:
+                    // "Z" means equal to UTC
+                    break;
+            }
+        }
+
+        calendar.set(year, month, day, hours, minutes, seconds);
+
+        return DateFormat
+                .getDateTimeInstance(DateFormat.DEFAULT, DateFormat.LONG)
+                .format(calendar.getTime());
+    }
+}

app/src/main/java/org/grapheneos/pdfviewer/fragment/DocumentPropertiesFragment.java

@@ -0,0 +1,60 @@
+package org.grapheneos.pdfviewer.fragment;
+
+import android.app.Activity;
+import android.app.Dialog;
+import android.os.Bundle;
+import android.widget.ArrayAdapter;
+
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.DialogFragment;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.grapheneos.pdfviewer.R;
+
+public class DocumentPropertiesFragment extends DialogFragment {
+    public static final String TAG = "DocumentPropertiesFragment";
+
+    private static final String KEY_DOCUMENT_PROPERTIES = "key_document_properties";
+
+    private static DocumentPropertiesFragment sDocumentPropertiesFragment;
+
+    private List<String> mDocumentProperties;
+
+    public static DocumentPropertiesFragment getInstance(final ArrayList<CharSequence> metaData) {
+        if (sDocumentPropertiesFragment == null) {
+            sDocumentPropertiesFragment = new DocumentPropertiesFragment();
+            final Bundle args = new Bundle();
+            args.putCharSequenceArrayList(KEY_DOCUMENT_PROPERTIES, metaData);
+            sDocumentPropertiesFragment.setArguments(args);
+        } else {
+            final Bundle args = sDocumentPropertiesFragment.getArguments();
+            args.clear();
+            args.putCharSequenceArrayList(KEY_DOCUMENT_PROPERTIES, metaData);
+        }
+        return sDocumentPropertiesFragment;
+    }
+
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        mDocumentProperties = getArguments().getStringArrayList(KEY_DOCUMENT_PROPERTIES);
+    }
+
+    @Override
+    public Dialog onCreateDialog(Bundle savedInstanceState) {
+        final Activity activity = getActivity();
+        final AlertDialog.Builder dialog = new AlertDialog.Builder(activity)
+                .setPositiveButton(android.R.string.ok, null);
+
+        if (mDocumentProperties != null) {
+            dialog.setTitle(getString(R.string.action_view_document_properties));
+            dialog.setAdapter(new ArrayAdapter<>(activity, android.R.layout.simple_list_item_1,
+                    mDocumentProperties), null);
+        } else {
+            dialog.setTitle(R.string.document_properties_retrieval_failed);
+        }
+        return dialog.create();
+    }
+}

app/src/main/java/org/grapheneos/pdfviewer/fragment/JumpToPageFragment.java

@@ -0,0 +1,66 @@
+package org.grapheneos.pdfviewer.fragment;
+
+import android.app.Dialog;
+import android.content.DialogInterface;
+import android.os.Bundle;
+import android.view.Gravity;
+import android.widget.FrameLayout;
+import android.widget.NumberPicker;
+
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.DialogFragment;
+
+import org.grapheneos.pdfviewer.PdfViewer;
+
+public class JumpToPageFragment extends DialogFragment {
+    public static final String TAG = "JumpToPageFragment";
+
+    private final static String STATE_PICKER_CUR = "picker_cur";
+    private final static String STATE_PICKER_MIN = "picker_min";
+    private final static String STATE_PICKER_MAX = "picker_max";
+
+    private NumberPicker mPicker;
+
+    @Override
+    public void onActivityCreated(Bundle savedInstanceState) {
+        super.onActivityCreated(savedInstanceState);
+        if (savedInstanceState != null) {
+            mPicker.setMinValue(savedInstanceState.getInt(STATE_PICKER_MIN));
+            mPicker.setMaxValue(savedInstanceState.getInt(STATE_PICKER_MAX));
+            mPicker.setValue(savedInstanceState.getInt(STATE_PICKER_CUR));
+        }
+    }
+
+    @Override
+    public Dialog onCreateDialog(Bundle savedInstanceState) {
+        mPicker = new NumberPicker(getActivity());
+        mPicker.setMinValue(1);
+        mPicker.setMaxValue(((PdfViewer)getActivity()).mNumPages);
+        mPicker.setValue(((PdfViewer)getActivity()).mPage);
+
+        final FrameLayout layout = new FrameLayout(getActivity());
+        layout.addView(mPicker, new FrameLayout.LayoutParams(
+                FrameLayout.LayoutParams.WRAP_CONTENT,
+                FrameLayout.LayoutParams.WRAP_CONTENT,
+                Gravity.CENTER));
+
+        return new AlertDialog.Builder(getActivity())
+                .setView(layout)
+                .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
+                    @Override
+                    public void onClick(DialogInterface dialogInterface, int i) {
+                        mPicker.clearFocus();
+                        ((PdfViewer)getActivity()).onJumpToPageInDocument(mPicker.getValue());
+                    }
+                })
+                .setNegativeButton(android.R.string.cancel, null)
+                .create();
+    }
+
+    @Override
+    public void onSaveInstanceState(Bundle outState) {
+        outState.putInt(STATE_PICKER_MIN, mPicker.getMinValue());
+        outState.putInt(STATE_PICKER_MAX, mPicker.getMaxValue());
+        outState.putInt(STATE_PICKER_CUR, mPicker.getValue());
+    }
+}

app/src/main/java/org/grapheneos/pdfviewer/loader/DocumentPropertiesLoader.java

@@ -0,0 +1,149 @@
+package org.grapheneos.pdfviewer.loader;
+
+import android.content.Context;
+import android.database.Cursor;
+import android.graphics.Typeface;
+import android.net.Uri;
+import android.provider.OpenableColumns;
+import android.text.SpannableStringBuilder;
+import android.text.Spanned;
+import android.text.style.StyleSpan;
+import android.util.Log;
+
+import androidx.loader.content.AsyncTaskLoader;
+
+import org.json.JSONException;
+import org.json.JSONObject;
+
+import java.text.ParseException;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.grapheneos.pdfviewer.R;
+import org.grapheneos.pdfviewer.Utils;
+
+public class DocumentPropertiesLoader extends AsyncTaskLoader<List<CharSequence>> {
+    public static final String TAG = "DocumentPropertiesLoader";
+
+    public static final int ID = 1;
+
+    private final String mProperties;
+    private final int mNumPages;
+    private final Uri mUri;
+
+    private Cursor mCursor;
+
+    public DocumentPropertiesLoader(Context context, String properties, int numPages, Uri uri) {
+        super(context);
+
+        mProperties = properties;
+        mNumPages = numPages;
+        mUri = uri;
+    }
+
+    @Override
+    public List<CharSequence> loadInBackground() {
+        final Context context = getContext();
+
+        final String[] names = context.getResources().getStringArray(R.array.property_names);
+        final List<CharSequence> properties = new ArrayList<>(names.length);
+
+        mCursor = context.getContentResolver().query(mUri, null, null, null, null);
+        if (mCursor != null) {
+            mCursor.moveToFirst();
+
+            final int indexName = mCursor.getColumnIndex(OpenableColumns.DISPLAY_NAME);
+            if (indexName >= 0) {
+                properties.add(getProperty(null, names[0], mCursor.getString(indexName)));
+            }
+
+            final int indexSize = mCursor.getColumnIndex(OpenableColumns.SIZE);
+            if (indexSize >= 0) {
+                final long fileSize = Long.valueOf(mCursor.getString(indexSize));
+                properties.add(getProperty(null, names[1], Utils.parseFileSize(fileSize)));
+            }
+
+            mCursor.close();
+        }
+
+        try {
+            final JSONObject json = new JSONObject(mProperties);
+
+            properties.add(getProperty(json, names[2], "Title"));
+            properties.add(getProperty(json, names[3], "Author"));
+            properties.add(getProperty(json, names[4], "Subject"));
+            properties.add(getProperty(json, names[5], "Keywords"));
+            properties.add(getProperty(json, names[6], "CreationDate"));
+            properties.add(getProperty(json, names[7], "ModDate"));
+            properties.add(getProperty(json, names[8], "Producer"));
+            properties.add(getProperty(json, names[9], "Creator"));
+            properties.add(getProperty(json, names[10], "PDFFormatVersion"));
+            properties.add(getProperty(null, names[11], String.valueOf(mNumPages)));
+
+            return properties;
+        } catch (JSONException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+
+    @Override
+    public void deliverResult(List<CharSequence> properties) {
+        if (isReset()) {
+            onReleaseResources();
+        } else if (isStarted()) {
+            super.deliverResult(properties);
+        }
+    }
+
+    @Override
+    protected void onStartLoading() {
+        forceLoad();
+    }
+
+    @Override
+    protected void onStopLoading() {
+        cancelLoad();
+    }
+
+    @Override
+    public void onCanceled(List<CharSequence> properties) {
+        super.onCanceled(properties);
+
+        onReleaseResources();
+    }
+
+    @Override
+    protected void onReset() {
+        super.onReset();
+
+        onStopLoading();
+        onReleaseResources();
+    }
+
+    private void onReleaseResources() {
+        if (mCursor != null) {
+            mCursor.close();
+            mCursor = null;
+        }
+    }
+
+    private CharSequence getProperty(final JSONObject json, String name, String specName) {
+        final SpannableStringBuilder property = new SpannableStringBuilder(name).append(":\n");
+        final String value = json != null ? json.optString(specName, "-") : specName;
+
+        if (specName.endsWith("Date")) {
+            final Context context = getContext();
+            try {
+                property.append(value.equals("-") ? value : Utils.parseDate(value));
+            } catch (ParseException e) {
+                Log.w(TAG, e.getMessage() + " for " + value + " at offset: " + e.getErrorOffset());
+                property.append(context.getString(R.string.document_properties_invalid_date));
+            }
+        } else {
+            property.append(value);
+        }
+        property.setSpan(new StyleSpan(Typeface.BOLD), 0, name.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
+        return property;
+    }
+}

app/src/main/res/drawable/ic_launcher_foreground.xml

@@ -0,0 +1,16 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="108dp"
+        android:height="108dp"
+        android:viewportWidth="31.16883"
+        android:viewportHeight="31.16883">
+    <group android:translateX="3.5844157"
+            android:translateY="3.5844157">
+        <path
+            android:pathData="M4.734,7.125h15.594v10.625h-15.594z"
+            android:fillAlpha="1"
+            android:fillColor="#ffffff"/>
+        <path
+            android:pathData="M7,11.5h1v-1L7,10.5v1zM19,3L5,3c-1.1,0 -2,0.9 -2,2v14c0,1.1 0.9,2 2,2h14c1.1,0 2,-0.9 2,-2L21,5c0,-1.1 -0.9,-2 -2,-2zM9.5,11.5c0,0.83 -0.67,1.5 -1.5,1.5L7,13v2L5.5,15L5.5,9L8,9c0.83,0 1.5,0.67 1.5,1.5v1zM19.5,10.5L17,10.5v1h1.5L18.5,13L17,13v2h-1.5L15.5,9h4v1.5zM14.5,13.5c0,0.83 -0.67,1.5 -1.5,1.5h-2.5L10.5,9L13,9c0.83,0 1.5,0.67 1.5,1.5v3zM12,13.5h1v-3h-1v3z"
+            android:fillColor="#000000"/>
+    </group>
+</vector>

app/src/main/res/layout/webview.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<WebView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/webview"
+    android:layout_width="fill_parent"
+    android:layout_height="fill_parent" />

app/src/main/res/menu/pdf_viewer.xml

@@ -0,0 +1,51 @@
+<menu xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:android="http://schemas.android.com/apk/res/android" >
+
+    <!--<item-->
+        <!--android:id="@+id/action_settings"-->
+        <!--android:orderInCategory="100"-->
+        <!--android:showAsAction="never"-->
+        <!--android:title="@string/action_settings"/>-->
+
+    <item
+        android:id="@+id/action_previous"
+        android:icon="@drawable/ic_navigate_before_white_24dp"
+        android:title="@string/action_previous"
+        app:showAsAction="ifRoom" />
+
+    <item
+        android:id="@+id/action_next"
+        android:icon="@drawable/ic_navigate_next_white_24dp"
+        android:title="@string/action_next"
+        app:showAsAction="ifRoom" />
+
+    <item
+        android:id="@+id/action_open"
+        android:icon="@drawable/ic_insert_drive_file_white_24dp"
+        android:title="@string/action_open"
+        app:showAsAction="ifRoom" />
+
+    <item
+        android:id="@+id/action_zoom_out"
+        android:icon="@drawable/ic_zoom_out_white_24dp"
+        android:title="@string/action_zoom_out"
+        app:showAsAction="ifRoom" />
+
+    <item
+        android:id="@+id/action_zoom_in"
+        android:icon="@drawable/ic_zoom_in_white_24dp"
+        android:title="@string/action_zoom_in"
+        app:showAsAction="ifRoom" />
+
+    <item
+        android:id="@+id/action_jump_to_page"
+        android:icon="@drawable/ic_pageview_white_24dp"
+        android:title="@string/action_jump_to_page"
+        app:showAsAction="ifRoom" />
+
+    <item
+        android:id="@+id/action_view_document_properties"
+        android:title="@string/action_view_document_properties"
+        app:showAsAction="never" />
+
+</menu>

app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@color/ic_launcher_background"/>
+    <foreground android:drawable="@drawable/ic_launcher_foreground"/>
+</adaptive-icon>

app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@color/ic_launcher_background"/>
+    <foreground android:drawable="@drawable/ic_launcher_foreground"/>
+</adaptive-icon>

app/src/main/res/values/arrays.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string-array name="property_names">
+        <item>File name</item>
+        <item>File size</item>
+        <item>Title</item>
+        <item>Author</item>
+        <item>Subject</item>
+        <item>Keywords</item>
+        <item>Creation date</item>
+        <item>Modify date</item>
+        <item>Producer</item>
+        <item>Creator</item>
+        <item>PDF version</item>
+        <item>Pages</item>
+    </string-array>
+</resources>

app/src/main/res/values/ic_launcher_background.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="ic_launcher_background">#000000</color>
+</resources>

app/src/main/res/values/strings.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="app_name">PDF Viewer</string>
+    <!--<string name="action_settings">Settings</string>-->
+    <string name="action_previous">Previous page</string>
+    <string name="action_next">Next page</string>
+    <string name="action_open">Open document</string>
+    <string name="action_zoom_out">Zoom out</string>
+    <string name="action_zoom_in">Zoom in</string>
+    <string name="action_jump_to_page">Jump to page</string>
+    <string name="action_view_document_properties">Properties</string>
+
+    <string name="document_properties_invalid_date">Invalid date</string>
+    <string name="document_properties_retrieval_failed">Failed to obtain document metadata</string>
+</resources>

app/src/main/res/values/styles.xml

@@ -0,0 +1,8 @@
+<resources>
+
+    <!-- Base application theme. -->
+    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
+        <!-- Customize your theme here. -->
+    </style>
+
+</resources>

build.gradle

@@ -0,0 +1,31 @@
+// Top-level build file where you can add configuration options common to all sub-projects/modules.
+
+buildscript {
+    repositories {
+        google()
+        jcenter()
+    }
+    dependencies {
+        classpath 'com.android.tools.build:gradle:3.4.1'
+
+        // NOTE: Do not place your application dependencies here; they belong
+        // in the individual module build.gradle files
+    }
+}
+
+allprojects {
+    repositories {
+        google()
+        jcenter()
+    }
+
+    gradle.projectsEvaluated {
+        tasks.withType(JavaCompile) {
+            options.compilerArgs << "-Xlint:unchecked" << "-Xlint:deprecation"
+        }
+    }
+}
+
+task clean(type: Delete) {
+    delete rootProject.buildDir
+}

gradle.properties

@@ -0,0 +1,2 @@
+android.enableJetifier=true
+android.useAndroidX=true

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.4.1-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

gradlew

@@ -0,0 +1,188 @@
+#!/usr/bin/env sh
+
+#
+# Copyright 2015 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"

gradlew.bat

@@ -0,0 +1,100 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      http://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

settings.gradle

@@ -0,0 +1 @@
+include ':app'