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/*
* The MIT License (MIT)
*
* Copyright (c) 2015 - Nathan Barraille
*
* 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.
*/
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import com.facebook.drawee.view.SimpleDraweeView;
/**
* A SimpleDraweeView that supports Pinch to zoom.
*/
public class PinchToZoomDraweeView extends SimpleDraweeView {
private final ScaleGestureDetector mScaleDetector;
private final ScaleGestureDetector.OnScaleGestureListener mScaleListener;
private float mCurrentScale;
private final Matrix mCurrentMatrix;
private float mMidX;
private float mMidY;
@Nullable private OnZoomChangeListener mListener;
public PinchToZoomDraweeView(Context context) {
this(context, null);
}
public PinchToZoomDraweeView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public PinchToZoomDraweeView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mScaleListener = new ScaleGestureDetector.SimpleOnScaleGestureListener() {
@Override
public boolean onScale(ScaleGestureDetector detector) {
float scaleFactor = detector.getScaleFactor();
float newScale = mCurrentScale * scaleFactor;
// Prevent from zooming out more than original
if (newScale > 1.0f) {
// We initialize this lazily so that we don't have to register (and force the user
// to unregister) a global layout listener on the view.
if (mMidX == 0.0f) {
mMidX = getWidth() / 2.0f;
}
if (mMidY == 0.0f) {
mMidY = getHeight() / 2.0f;
}
mCurrentScale = newScale;
mCurrentMatrix.postScale(scaleFactor, scaleFactor, mMidX, mMidY);
invalidate();
} else {
scaleFactor = 1.0f / mCurrentScale;
reset();
}
if (mListener != null && scaleFactor != 1.0f) {
mListener.onZoomChange(mCurrentScale);
}
return true;
}
};
mScaleDetector = new ScaleGestureDetector(getContext(), mScaleListener);
mCurrentMatrix = new Matrix();
}
public void setOnZoomChangeListener(OnZoomChangeListener listener) {
mListener = listener;
}
@Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
setOnZoomChangeListener(null);
}
@Override
protected void onDraw(@NonNull Canvas canvas) {
int saveCount = canvas.save();
canvas.concat(mCurrentMatrix);
super.onDraw(canvas);
canvas.restoreToCount(saveCount);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
return mScaleDetector.onTouchEvent(event) || super.onTouchEvent(event);
}
/**
* Resets the zoom on that view
*/
public void resetZoom() {
reset();
}
/**
* Resets the zoom of the attached image.
* This has no effect if the image has been destroyed
*/
public void reset() {
mCurrentMatrix.reset();
mCurrentScale = 1.0f;
invalidate();
}
/**
* A listener interface for when the zoom scale changes
*/
public interface OnZoomChangeListener {
/**
* Callback method getting triggered when the zoom scale changes.
* This is not called when the zoom is programmatically reset
* @param scale the new scale
*/
public void onZoomChange(float scale);
}
}

hendrawd commented Oct 2, 2015

It will be useful if you can add a functionality to make the image move by drag. For now, it's only zooming with anchor center. Thanks anyway for the gist :)

Edit : Ok, so it is an example of how to pinch zoom drawee view. I got the solution for pinch zoom and drag image https://github.com/facebook/fresco/blob/master/samples/zoomable/src/main/java/com/facebook/samples/zoomable/ZoomableDraweeView.java if anyone want to use.

@nbarraille
Thank you for code.

@hendrawd
Please not if are going to use in commercial project.
This file provided by Facebook is for non-commercial testing and evaluation purposes only. Facebook reserves all rights not expressly granted.

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