add immersive mode

app/src/main/assets/viewer.js

@@ -185,6 +185,10 @@ function onRenderPage(lazy) {
     }
 }
 
+function isTextSelected() {
+    return window.getSelection().toString() !== "";
+}
+
 pdfjsLib.getDocument("https://localhost/placeholder.pdf").promise.then(function(newDoc) {
     pdfDoc = newDoc;
     channel.setNumPages(pdfDoc.numPages);

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

@@ -8,10 +8,13 @@ import android.graphics.Color;
 import android.net.Uri;
 import android.os.Bundle;
 import android.util.Log;
+import android.view.GestureDetector;
 import android.view.Gravity;
 import android.view.Menu;
 import android.view.MenuInflater;
 import android.view.MenuItem;
+import android.view.MotionEvent;
+import android.view.View;
 import android.webkit.CookieManager;
 import android.webkit.JavascriptInterface;
 import android.webkit.WebResourceRequest;
@@ -28,7 +31,6 @@ 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;
 
@@ -138,7 +140,7 @@ public class PdfViewer extends AppCompatActivity implements LoaderManager.Loader
     }
 
     @Override
-    @SuppressLint("SetJavaScriptEnabled")
+    @SuppressLint({"SetJavaScriptEnabled", "ClickableViewAccessibility"})
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
 
@@ -217,6 +219,31 @@ public class PdfViewer extends AppCompatActivity implements LoaderManager.Loader
             }
         });
 
+        final GestureDetector detector = new GestureDetector(PdfViewer.this,
+                new GestureDetector.SimpleOnGestureListener() {
+                    @Override
+                    public boolean onSingleTapUp(MotionEvent motionEvent) {
+                        if (mUri != null) {
+                            mWebView.evaluateJavascript("isTextSelected()", selection -> {
+                                if (!Boolean.valueOf(selection)) {
+                                    if ((getWindow().getDecorView().getSystemUiVisibility() &
+                                            View.SYSTEM_UI_FLAG_FULLSCREEN) == 0) {
+                                        hideSystemUi();
+                                    } else {
+                                        showSystemUi();
+                                    }
+                                }
+                            });
+                            return true;
+                        }
+                        return false;
+                    }
+                });
+        mWebView.setOnTouchListener((view, motionEvent) -> {
+            detector.onTouchEvent(motionEvent);
+            return false;
+        });
+
         mTextView = new TextView(this);
         mTextView.setBackgroundColor(Color.DKGRAY);
         mTextView.setTextColor(ColorStateList.valueOf(Color.WHITE));
@@ -318,6 +345,23 @@ public class PdfViewer extends AppCompatActivity implements LoaderManager.Loader
         }
     }
 
+    private void showSystemUi() {
+        getWindow().getDecorView().setSystemUiVisibility(
+                View.SYSTEM_UI_FLAG_LAYOUT_STABLE |
+                View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION |
+                View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
+    }
+
+    private void hideSystemUi() {
+        getWindow().getDecorView().setSystemUiVisibility(
+                View.SYSTEM_UI_FLAG_LAYOUT_STABLE |
+                View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION |
+                View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN |
+                View.SYSTEM_UI_FLAG_HIDE_NAVIGATION |
+                View.SYSTEM_UI_FLAG_FULLSCREEN |
+                View.SYSTEM_UI_FLAG_IMMERSIVE);
+    }
+
     @Override
     public void onSaveInstanceState(Bundle savedInstanceState) {
         super.onSaveInstanceState(savedInstanceState);