让 fresco 支持双指缩放与拖动
需求
fresco 的 SimpleDraweeView 不支持缩放与拖动，想尽可能简单的实现这个功能
代码
ZoomableDraweeView.java
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package com.xmeise.mm;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.support.annotation.NonNull;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import com.facebook.drawee.view.SimpleDraweeView;
/*
* The MIT License (MIT)
*
* Copyright (c) 2015 - Nathan Barraille, jk2K
*
* 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.
*/
public class ZoomableDraweeView extends SimpleDraweeView {
private ScaleGestureDetector mScaleDetector;
private GestureDetector mGestureDetector;
private float mCurrentScale = 1.0f;
private Matrix mCurrentMatrix;
private float mMidX;
private float mMidY;
private OnClickListener mClickListener;
private OnLongPressListener mLongPressListener;
public ZoomableDraweeView(Context context) {
this(context, null);
}
public ZoomableDraweeView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public ZoomableDraweeView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init();
}
private void init() {
ScaleGestureDetector.OnScaleGestureListener 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;
// support pinch zoom
mCurrentMatrix.postScale(scaleFactor, scaleFactor, mMidX, mMidY);
invalidate();
} else {
scaleFactor = 1.0f / mCurrentScale;
reset();
}
return true;
}
};
mScaleDetector = new ScaleGestureDetector(getContext(), mScaleListener);
mCurrentMatrix = new Matrix();
GestureDetector.SimpleOnGestureListener mGestureListener = new GestureDetector.SimpleOnGestureListener() {
public void onLongPress (MotionEvent e) {
// support long press listener
if (mLongPressListener != null) {
mLongPressListener.onLongPress();
}
}
public boolean onSingleTapConfirmed (MotionEvent e) {
// support single tap listener
if (mClickListener != null) {
mClickListener.onClick();
}
return true;
}
public boolean onScroll (MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
// support drag
// disable drag when normal scale
if (mCurrentScale > 1.0f) {
mCurrentMatrix.postTranslate(-distanceX, -distanceY);
invalidate();
}
return true;
}
};
mGestureDetector = new GestureDetector(getContext(), mGestureListener);
}
@Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
}
@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) {
mScaleDetector.onTouchEvent(event);
if (!mScaleDetector.isInProgress()) {
mGestureDetector.onTouchEvent(event);
}
return true;
}
/**
* 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();
}
public void setOnLongPressListener(OnLongPressListener listener) {
mLongPressListener = listener;
}
public interface OnLongPressListener {
void onLongPress();
}
public void setOnClickListener(OnClickListener listener) {
mClickListener = listener;
}
public interface OnClickListener {
void onClick();
}
}
说明
在 PinchToZoomScaleDetector.java 的基础上实现了拖动操作, 不是很难, 在这个过程中最大的收获就是了解了ScaleGestureDetector和GestureDetector该如何使用, 好的, 尽情使用吧
参考链接
本文由作者按照 CC BY 4.0 进行授权
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