64 lines
2.1 KiB
Java
64 lines
2.1 KiB
Java
package app.grapheneos.pdfviewer;
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import android.annotation.SuppressLint;
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import android.content.Context;
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import android.view.ScaleGestureDetector;
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import android.view.View;
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/*
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The GestureHelper present a simple gesture api for the PdfViewer
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*/
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class GestureHelper {
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public interface GestureListener {
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// Can be replaced with ratio when supported
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void onZoomIn(float value);
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void onZoomOut(float value);
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void onZoomEnd();
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}
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@SuppressLint("ClickableViewAccessibility")
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static void attach(Context context, View gestureView, GestureListener listener) {
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final ScaleGestureDetector scaleDetector = new ScaleGestureDetector(context,
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new ScaleGestureDetector.SimpleOnScaleGestureListener() {
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final float SPAN_RATIO = 600;
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float initialSpan;
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float prevNbStep;
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@Override
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public boolean onScaleBegin(ScaleGestureDetector detector) {
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initialSpan = detector.getCurrentSpan();
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prevNbStep = 0;
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return true;
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}
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@Override
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public boolean onScale(ScaleGestureDetector detector) {
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float spanDiff = initialSpan - detector.getCurrentSpan();
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float curNbStep = spanDiff / SPAN_RATIO;
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float stepDiff = curNbStep - prevNbStep;
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if (stepDiff > 0) {
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listener.onZoomOut(stepDiff);
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} else {
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listener.onZoomIn(Math.abs(stepDiff));
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}
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prevNbStep = curNbStep;
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return true;
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}
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@Override
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public void onScaleEnd(ScaleGestureDetector detector) {
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listener.onZoomEnd();
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}
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});
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gestureView.setOnTouchListener((view, motionEvent) -> {
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scaleDetector.onTouchEvent(motionEvent);
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return false;
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});
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}
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}
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