这期内容当中小编将会给大家带来有关ImageView如何在Android应用中使用，文章内容丰富且以专业的角度为大家分析和叙述，阅读完这篇文章希望大家可以有所收获。
MatrixImageView类改改代码了：
public class MatrixImageView extends ImageView { private static final int MODE_NONE = 190; private static final int MODE_DRAG = 468; private static final int MODE_ZOOM = 685; private int mode; private float startX, startY; private float midX, midY; private Matrix currMatrix, savedMatrix; private float preRotate, rotate; private float preSpacing; private GestureDetector detector; public MatrixImageView(Context context, AttributeSet attrs) { super(context, attrs); initView(); detector=new GestureDetector(context,onGestureListener); } private void initView() { mode = MODE_NONE; currMatrix = new Matrix(); savedMatrix = new Matrix(); DisplayMetrics dm = getResources().getDisplayMetrics(); Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.test); bitmap = Bitmap.createScaledBitmap(bitmap, dm.widthPixels, dm.heightPixels, true); setImageBitmap(bitmap); } @Override public boolean onTouchEvent(MotionEvent event) { return detector.onTouchEvent(event); } private GestureDetector.SimpleOnGestureListener onGestureListener=new GestureDetector.SimpleOnGestureListener(){ @Override public boolean onSingleTapUp(MotionEvent e) { Log.e("TAG", "====onSingleTapUp====="); return super.onSingleTapUp(e); } @Override public void onLongPress(MotionEvent e) { Log.e("TAG", "====onLongPress====="); super.onLongPress(e); } @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { Log.e("TAG", "====onScroll====="); Log.e("TAG", "distanceX===>"+distanceX); Log.e("TAG", "distanceY===>"+distanceY); return super.onScroll(e1, e2, distanceX, distanceY); } @Override public void onShowPress(MotionEvent e) { Log.e("TAG", "====onShowPress====="); super.onShowPress(e); } @Override public boolean onDown(MotionEvent e) { Log.e("TAG", "====onDown====="); return true; } @Override public boolean onDoubleTap(MotionEvent e) { Log.e("TAG", "====onDoubleTap====="); return super.onDoubleTap(e); } @Override public boolean onDoubleTapEvent(MotionEvent e) { Log.e("TAG", "====onDoubleTapEvent====="); return super.onDoubleTapEvent(e); } @Override public boolean onSingleTapConfirmed(MotionEvent e) { Log.e("TAG", "====onSingleTapConfirmed====="); return super.onSingleTapConfirmed(e); } @Override public boolean onContextClick(MotionEvent e) { Log.e("TAG", "====onContextClick====="); return super.onContextClick(e); } @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { Log.e("TAG", "====onFling====="); Log.e("TAG", "velocityX===>"+velocityX); Log.e("TAG", "velocityY===>"+velocityY); return super.onFling(e1, e2, velocityX, velocityY); } };}首先我们在构造方法中创建一个手势监测器的对象GestureDetector:
public MatrixImageView(Context context, AttributeSet attrs) { super(context, attrs); initView(); detector=new GestureDetector(context,onGestureListener); }GestureDetector既然是监听我们的手势的工具类，那我们是不是得把我们得手势交给它呢？ 是的！！ 于是我们在onTouchEvent中把事件交给GestureDetector：
@Override public boolean onTouchEvent(MotionEvent event) { return detector.onTouchEvent(event); }那我们把事件交给了GestureDetector，GestureDetector处理完毕后我们怎么知道呢？ 还记得我们创建GestureDetector对象的时候传递的参数吗？
detector=new GestureDetector(context,onGestureListener);
我们传递给了GestureDetector一个onGestureListener对象，GestureDetector检查完毕手势后，会调用onGestureListener中的方法进行回调，我们只需要在onGestureListener对象的相应方法中作出处理就可以了：
private GestureDetector.SimpleOnGestureListener onGestureListener=new GestureDetector.SimpleOnGestureListener(){ @Override public boolean onSingleTapUp(MotionEvent e) { Log.e(“TAG”, “====onSingleTapUp=====”); return super.onSingleTapUp(e); } @Override public void onLongPress(MotionEvent e) { Log.e("TAG", "====onLongPress====="); super.onLongPress(e); } @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { Log.e("TAG", "====onScroll====="); Log.e("TAG", "distanceX===>"+distanceX); Log.e("TAG", "distanceY===>"+distanceY); return super.onScroll(e1, e2, distanceX, distanceY); } @Override public void onShowPress(MotionEvent e) { Log.e("TAG", "====onShowPress====="); super.onShowPress(e); } @Override public boolean onDown(MotionEvent e) { Log.e("TAG", "====onDown====="); return super.onDown(e); } @Override public boolean onDoubleTap(MotionEvent e) { Log.e("TAG", "====onDoubleTap====="); return super.onDoubleTap(e); } @Override public boolean onDoubleTapEvent(MotionEvent e) { Log.e("TAG", "====onDoubleTapEvent====="); return super.onDoubleTapEvent(e); } @Override public boolean onSingleTapConfirmed(MotionEvent e) { Log.e("TAG", "====onSingleTapConfirmed====="); return super.onSingleTapConfirmed(e); } @Override public boolean onContextClick(MotionEvent e) { Log.e("TAG", "====onContextClick====="); return super.onContextClick(e); } @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { Log.e("TAG", "====onFling====="); Log.e("TAG", "velocityX===>"+velocityX); Log.e("TAG", "velocityY===>"+velocityY); return super.onFling(e1, e2, velocityX, velocityY); }};我们先不管其中方法啥时候调用，我们先重写它的所有方法，然后打上log，看看我们手指操作后相应的回调，于是我们运行代码：
是的，没错！就只是一张图片，因为我们也只是显示了一张图片：
我们轻轻的点击一下屏幕：
03-02 20:47:41.367 1798-1798/com.leo.gestureimageview E/TAG: ====onDown=====
03-02 20:47:41.466 1798-1798/com.leo.gestureimageview E/TAG: ====onShowPress=====
03-02 20:47:41.967 1798-1798/com.leo.gestureimageview E/TAG: ====onLongPress=====
轻轻的点击一下屏幕：
我们可以看到log执行顺序：onDown->onShowPress－>onLongPress
我们点击屏幕按下，然后过一会再放开：
03-02 21:51:27.121 17138-17138/com.leo.gestureimageview E/TAG: ====onDown=====
03-02 21:51:27.222 17138-17138/com.leo.gestureimageview E/TAG: ====onShowPress=====
03-02 21:51:27.722 17138-17138/com.leo.gestureimageview E/TAG: ====onLongPress=====
我们滑动一下手指：
03-02 21:51:27.121 17138-17138/com.leo.gestureimageview E/TAG: ====onDown=====
03-02 21:51:27.222 17138-17138/com.leo.gestureimageview E/TAG: ====onShowPress=====
03-02 21:51:27.722 17138-17138/com.leo.gestureimageview E/TAG: ====onLongPress=====
不管我们怎么样操作，打印的log总是这三个方法？ 这是咋回事呢？ 如果看到这里你有疑问的话，那我告诉你，你Android事件传递机制掌握的还不是很好，为什么这么说呢？？ 下面我们带着疑问看看源码：
猜都可以猜到GestureDetector处理手势的代码肯定在onTouchEvent方法中，那么我们看一下onTouchEvent方法：
public boolean onTouchEvent(MotionEvent ev) { if (mDoubleTapListener != null) { boolean hadTapMessage = mHandler.hasMessages(TAP); if (hadTapMessage) mHandler.removeMessages(TAP); if ((mCurrentDownEvent != null) && (mPreviousUpEvent != null) && hadTapMessage && isConsideredDoubleTap(mCurrentDownEvent, mPreviousUpEvent, ev)) { // This is a second tap mIsDoubleTapping = true; // Give a callback with the first tap of the double-tap handled |= mDoubleTapListener.onDoubleTap(mCurrentDownEvent); // Give a callback with down event of the double-tap handled |= mDoubleTapListener.onDoubleTapEvent(ev); } else { // This is a first tap mHandler.sendEmptyMessageDelayed(TAP, DOUBLE_TAP_TIMEOUT); } } mDownFocusX = mLastFocusX = focusX; mDownFocusY = mLastFocusY = focusY; if (mCurrentDownEvent != null) { mCurrentDownEvent.recycle(); } mCurrentDownEvent = MotionEvent.obtain(ev); mAlwaysInTapRegion = true; mAlwaysInBiggerTapRegion = true; mStillDown = true; mInLongPress = false; mDeferConfirmSingleTap = false; if (mIsLongpressEnabled) { mHandler.removeMessages(LONG_PRESS); mHandler.sendEmptyMessageAtTime(LONG_PRESS, mCurrentDownEvent.getDownTime() + TAP_TIMEOUT + LONGPRESS_TIMEOUT); } mHandler.sendEmptyMessageAtTime(SHOW_PRESS, mCurrentDownEvent.getDownTime() + TAP_TIMEOUT); handled |= mListener.onDown(ev); break; }代码太多了，那为什么我们只收到了onDown、onShowPress、onLongPress这三个方法的回调呢？
我们知道，当我们手指刚按下屏幕的时候，ACTION_DOWN会执行，然后我们看到这么一行代码：
handled |= mListener.onDown(ev);
mListener是我们传递的SimpleOnGestureListener,于是就看到了控制台的第一个log：
03-02 21:51:29.706 17138-17138/com.leo.gestureimageview E/TAG: ====onDown=====
我们的onDown是打印了，然后handled |= mListener.onDown(ev);看一下我们返回的是什么值：
@Override public boolean onDown(MotionEvent e) { Log.e("TAG", "====onDown====="); return super.onDown(e); }我们直接返回了super.onDown(e)，接着我们看一下父类返回的是什么：
public boolean onDown(MotionEvent e) { return false; }可以看到，父类直接返回了false，所以handled此时为false，然后当ACTION_DOWN执行完毕后，就回到了我们的自定义view中的onTouchEvent方法中了：
@Override public boolean onTouchEvent(MotionEvent event) { return detector.onTouchEvent(event); }此时我们的view中的onTouchEvent 方法返回的是false，到了这里懂事件传递机制的小伙伴都懂，当我们的onTouchEvent返回了false的话，后面的事件都将接收不到了，也就是说只能执行ACTION_DOWN，那么有些小伙伴可能又要说了，那我把view的clickable或者longclickable设置成true，事件不就可以传递了么？
好的～！ 我们试一试：
<com.leo.gestureimageview.MatrixImageView android:clickable="true" android:layout_width="match_parent" android:layout_height="match_parent" android:scaleType="matrix" />运行代码，还是只打印了那三个方法，那这又是怎么回事呢？ 还记得我们view的onTouchEvent方法么？我们是这么写的：
@Override public boolean onTouchEvent(MotionEvent event) { return detector.onTouchEvent(event); }如果改成这样再试试：
@Override public boolean onTouchEvent(MotionEvent event) { detector.onTouchEvent(event); return super.onTouchEvent(event); }拖动手指返回结果：
好啦～！！ 终于看到我们久违的结果了，如果我们还是想用以前的写法，把onTouchEvent的返回结果交给GestureDetector处理该怎么做呢？
@Override public boolean onTouchEvent(MotionEvent event) { return detector.onTouchEvent(event); }我们只需要在回调方法的onDown中返回true即可：
@Override public boolean onDown(MotionEvent e) { Log.e("TAG", "====onDown====="); return true; }我们再次运行代码并拖动手指：
好啦～！ 说了那么多不知道小伙伴们理解了没？还是不理解的小伙伴可以去看看我前几篇事件传递的博客，嘻嘻～我们还是快点往下走吧….
我们长按一下屏幕然后提起手指：
03-02 22:29:37.361 22104-22104/com.leo.gestureimageview E/TAG: ====onDown=====
03-02 22:29:37.367 22104-22104/com.leo.gestureimageview E/TAG: ====onSingleTapUp=====
03-02 22:29:37.663 22104-22104/com.leo.gestureimageview E/TAG: ====onSingleTapConfirmed=====
执行了onDown=>onSingleTapUp=>onSingleTapConfirmed.
我们快速点击一下屏幕：
03-02 22:31:48.603 22104-22104/com.leo.gestureimageview E/TAG: ====onDown=====
03-02 22:31:48.610 22104-22104/com.leo.gestureimageview E/TAG: ====onSingleTapUp=====
03-02 22:31:48.903 22104-22104/com.leo.gestureimageview E/TAG: ====onSingleTapConfirmed=====
执行了onDown=>onSingleTapUp=>onSingleTapConfirmed.
然后我们再次滑动手指：
03-02 22:34:41.820 22104-22104/com.leo.gestureimageview E/TAG: ====onDown=====
03-02 22:34:41.920 22104-22104/com.leo.gestureimageview E/TAG: ====onShowPress=====
03-02 22:34:42.018 22104-22104/com.leo.gestureimageview E/TAG: ====onScroll=====
03-02 22:34:42.018 22104-22104/com.leo.gestureimageview E/TAG: distanceX===>-117.13138
03-02 22:34:42.018 22104-22104/com.leo.gestureimageview E/TAG: distanceY===>75.100464
03-02 22:34:42.036 22104-22104/com.leo.gestureimageview E/TAG: ====onScroll=====
03-02 22:34:42.036 22104-22104/com.leo.gestureimageview E/TAG: distanceX===>-75.859314
执行顺序：onDown＝》onShowPress＝》onScroll（很多次）
最后我们手指拖动距离长一点再快一点：
03-02 22:47:42.453 5103-5103/com.leo.gestureimageview E/TAG: distanceX===>-274.69336
03-02 22:47:42.453 5103-5103/com.leo.gestureimageview E/TAG: distanceY===>-0.34838867
03-02 22:47:42.460 5103-5103/com.leo.gestureimageview E/TAG: ====onFling=====
03-02 22:47:42.460 5103-5103/com.leo.gestureimageview E/TAG: velocityX===>27284.943
03-02 22:47:42.460 5103-5103/com.leo.gestureimageview E/TAG: velocityY===>-95.6131
前 面还有一段log没给出了，调用方法顺序为：onDown＝》onShowPress＝》onScroll（很多次）＝》最后松开手指的时候onFling（）；
好了～！ 到这里，我们的回调方法中还有几个没有被调用，就是监听双击事件的时候，于是我们双击屏幕：
03-02 22:50:34.786 5103-5103/com.leo.gestureimageview E/TAG: ====onDown=====
03-02 22:50:34.793 5103-5103/com.leo.gestureimageview E/TAG: ====onSingleTapUp=====
03-02 22:50:34.924 5103-5103/com.leo.gestureimageview E/TAG: ====onDoubleTap=====
03-02 22:50:34.924 5103-5103/com.leo.gestureimageview E/TAG: ====onDoubleTapEvent=====
03-02 22:50:34.924 5103-5103/com.leo.gestureimageview E/TAG: ====onDown=====
03-02 22:50:34.932 5103-5103/com.leo.gestureimageview E/TAG: ====onDoubleTapEvent=====
我们双击屏幕执行的方法为：
onDown=>onSingleTapUp=>onDoubleTap=>onDoubleTapEvent=>onDoubleTapEvent
可见，执行了一次onDoubleTap，两次onDoubleTapEvent
好啦～！ 看完了SimpleOnGestureListener中所有方法的回调，我们反过来再看一遍这些回调方法：
好啦~!说了那么api内容，下面写个小例子用一下GestureDetector：
package com.leo.gestureimageview;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Matrix;import android.util.AttributeSet;import android.util.DisplayMetrics;import android.util.Log;import android.view.GestureDetector;import android.view.MotionEvent;import android.widget.ImageView;public class MatrixImageView extends ImageView { private Matrix currMatrix; private GestureDetector detector; public MatrixImageView(Context context, AttributeSet attrs) { super(context, attrs); initView(); detector=new GestureDetector(context,onGestureListener); } private void initView() { currMatrix = new Matrix(); DisplayMetrics dm = getResources().getDisplayMetrics(); Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.test); bitmap = Bitmap.createScaledBitmap(bitmap, dm.widthPixels, dm.heightPixels, true); setImageBitmap(bitmap); } @Override public boolean onTouchEvent(MotionEvent event) { return detector.onTouchEvent(event); } private float currX; private float currY; private GestureDetector.SimpleOnGestureListener onGestureListener=new GestureDetector.SimpleOnGestureListener(){ @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { Log.e("TAG", "====onScroll====="); Log.e("TAG", "distanceX===>"+distanceX); Log.e("TAG", "distanceY===>"+distanceY); currX-=distanceX; currY-=distanceY; currMatrix.reset(); currMatrix.postTranslate(currX,currY); setImageMatrix(currMatrix); return super.onScroll(e1, e2, distanceX, distanceY); } };}上述就是小编为大家分享的ImageView如何在Android应用中使用了，如果刚好有类似的疑惑，不妨参照上述分析进行理解。如果想知道更多相关知识，欢迎关注编程网行业资讯频道。
