google 提供的API中，有个类，大家都很熟悉，GestureDetector。使用它，我们可以识别用户通常会用的手势。但是，这个类不支持多点触摸（可能 google认为没有人会在几个手指都在屏幕上的时候，使用手势吧~），不过，最近和朋友们一起做的一个App，的确用到了多点手势（主要是 onScroll和onFling两个手势），所以，我就把这个类拓展了一下，来实现让多个控件各自跟着一跟手指实现拖动和滑动的效果。  
  顺便说一下，大家应该都知道，在Android3.0以后，Android的触摸事件的分配机制和以前的版本是有区别的。从3.0开始，用户在不同控件上操作产生的touch消息不会相互干扰，touch消息会被分派到不同控件上的touchListener中处理。而  
在以前的版本中，所有的touch消息，都会被分排到第一个碰到屏幕的手指所操作的控件的touchListener中处理，也就是说，会出现这样一个矛盾的现象：  
  在界面上有A,B,C三个控件，然后，当你先用食指按住A，跟着又用中指和无名指（嘛，别的手指也行，不用在意中指还是无名指）按住B,C。当中指和无名指移动的时候，B和C都无法接收到这个ACTION_MOVE消息，而接收到消息的却是A。而在3.0以上版本中，并不存在这个问题。

使用以下的这个类，可以实现从2.2到3.2平台上手势识别的兼容。

package com.finger.utils;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.ViewConfiguration;
public class MultiTouchGestureDetector {@SuppressWarnings("unused")private static final String MYTAG = "Ray";public static final String CLASS_NAME = "MultiTouchGestureDetector";/*** 事件信息类 <br/>* 用来记录一个手势*/private class EventInfo {private MultiMotionEvent mCurrentDownEvent;    //当前的down事件private MultiMotionEvent mPreviousUpEvent;    //上一次up事件private boolean mStillDown;                    //当前手指是否还在屏幕上private boolean mInLongPress;                //当前事件是否属于长按手势private boolean mAlwaysInTapRegion;            //是否当前手指仅在小范围内移动，当手指仅在小范围内移动时，视为手指未曾移动过，不会触发onScroll手势private boolean mAlwaysInBiggerTapRegion;    //是否当前手指在较大范围内移动，仅当此值为true时，双击手势才能成立private boolean mIsDoubleTapping;            //当前手势，是否为双击手势private float mLastMotionY;                    //最后一次事件的X坐标private float mLastMotionX;                    //最后一次事件的Y坐标private EventInfo(MotionEvent e) {this(new MultiMotionEvent(e));}private EventInfo(MultiMotionEvent me) {mCurrentDownEvent = me;mStillDown = true;mInLongPress = false;mAlwaysInTapRegion = true;mAlwaysInBiggerTapRegion = true;mIsDoubleTapping = false;}//释放MotionEven对象，使系统能够继续使用它们public void recycle() {if (mCurrentDownEvent != null) {mCurrentDownEvent.recycle();mCurrentDownEvent = null;}if (mPreviousUpEvent != null) {mPreviousUpEvent.recycle();mPreviousUpEvent = null;}}@Overridepublic void finalize() {this.recycle();}}/*** 多点事件类 <br/>* 将一个多点事件拆分为多个单点事件，并方便获得事件的绝对坐标* <br/> 绝对坐标用以在界面中找到触点所在的控件* @author ray-ni*/public class MultiMotionEvent {private MotionEvent mEvent;private int mIndex;private MultiMotionEvent(MotionEvent e) {mEvent = e;mIndex = (e.getAction() & MotionEvent.ACTION_POINTER_ID_MASK) >> MotionEvent.ACTION_POINTER_ID_SHIFT;  //等效于 mEvent.getActionIndex();}private MultiMotionEvent(MotionEvent e, int idx) {mEvent = e;mIndex = idx;}// 行为public int getAction() {int action = mEvent.getAction() & MotionEvent.ACTION_MASK;    //等效于 mEvent.getActionMasked();switch (action) {case MotionEvent.ACTION_POINTER_DOWN:action = MotionEvent.ACTION_DOWN;break;case MotionEvent.ACTION_POINTER_UP:action = MotionEvent.ACTION_UP;break;}return action;}// 返回X的绝对坐标public float getX() {return mEvent.getX(mIndex) + mEvent.getRawX() - mEvent.getX();}// 返回Y的绝对坐标public float getY() {return mEvent.getY(mIndex) + mEvent.getRawY() - mEvent.getY();}// 事件发生的时间public long getEventTime() {return mEvent.getEventTime();}// 事件序号public int getIndex() {return mIndex;}// 事件IDpublic int getId() {return mEvent.getPointerId(mIndex);}// 释放事件对象，使系统能够继续使用public void recycle() {if (mEvent != null) {mEvent.recycle();mEvent = null;}}}// 多点手势监听器public interface MultiTouchGestureListener {// 手指触碰到屏幕，由一个 ACTION_DOWN触发boolean onDown(MultiMotionEvent e);// 确定一个press事件，强调手指按下的一段时间（TAP_TIMEOUT）内，手指未曾移动或抬起void onShowPress(MultiMotionEvent e);// 手指点击屏幕后离开，由 ACTION_UP引发，可以简单的理解为单击事件，即手指点击时间不长（未构成长按事件），也不曾移动过boolean onSingleTapUp(MultiMotionEvent e);// 长按，手指点下后一段时间（DOUBLE_TAP_TIMEOUT）内，不曾抬起或移动void onLongPress(MultiMotionEvent e);// 拖动，由ACTION_MOVE触发，手指地按下后，在屏幕上移动boolean onScroll(MultiMotionEvent e1, MultiMotionEvent e2, float distanceX, float distanceY);// 滑动，由ACTION_UP触发，手指按下并移动一段距离后，抬起时触发boolean onFling(MultiMotionEvent e1, MultiMotionEvent e2, float velocityX, float velocityY);}// 多点双击监听器public interface MultiTouchDoubleTapListener {// 单击事件确认，强调第一个单击事件发生后，一段时间内，未发生第二次单击事件，即确定不会触发双击事件boolean onSingleTapConfirmed(MultiMotionEvent e);// 双击事件， 由ACTION_DOWN触发，从第一次单击事件的DOWN事件开始的一段时间(DOUBLE_TAP_TIMEOUT)内结束（即手指），// 并且在第一次单击事件的UP时间开始后的一段时间内（DOUBLE_TAP_TIMEOUT）发生第二次单击事件，// 除此之外两者坐标间距小于定值（DOUBLE_TAP_SLAP）时，则触发双击事件boolean onDoubleTap(MultiMotionEvent e);// 双击事件，与onDoubleTap事件不同之处在于，构成双击的第二次点击的ACTION_DOWN,ACTION_MOVE和ACTION_UP都会触发该事件boolean onDoubleTapEvent(MultiMotionEvent e);}// 事件信息队列，队列的下标与MotionEvent的pointId对应private static List<EventInfo> sEventInfos = new ArrayList<EventInfo>(10);// 双击判断队列，这个队列中的元素等待双击超时的判断结果private static List<EventInfo> sEventForDoubleTap = new ArrayList<EventInfo>(5);// 指定大点击区域的大小（这个比较拗口），这个值主要用于帮助判断双击是否成立private int mBiggerTouchSlopSquare = 20 * 20;// 判断是否构成onScroll手势，当手指在这个范围内移动时，不触发onScroll手势private int mTouchSlopSquare;// 判断是否构成双击，只有两次点击的距离小于该值，才能构成双击手势private int mDoubleTapSlopSquare;// 最小滑动速度private int mMinimumFlingVelocity;// 最大滑动速度private int mMaximumFlingVelocity;// 长按阀值，当手指按下后，在该阀值的时间内，未移动超过mTouchSlopSquare的距离并未抬起，则长按手势触发private static final int LONGPRESS_TIMEOUT = ViewConfiguration.getLongPressTimeout();// showPress手势的触发阀值，当手指按下后，在该阀值的时间内，未移动超过mTouchSlopSquare的距离并未抬起，则showPress手势触发private static final int TAP_TIMEOUT = ViewConfiguration.getTapTimeout();// 双击超时阀值，仅在两次双击事件的间隔（第一次单击的UP事件和第二次单击的DOWN事件）小于此阀值，双击事件才能成立private static final int DOUBLE_TAP_TIMEOUT = ViewConfiguration.getDoubleTapTimeout();// 双击区域阀值，仅在两次双击事件的距离小于此阀值，双击事件才能成立private static final int DOUBLE_TAP_SLAP = 64;// GestureHandler所处理的Message的what属性可能为以下 常量：// showPress手势private static final int SHOW_PRESS = 1;// 长按手势private static final int LONG_PRESS = 2;// SingleTapConfirmed手势private static final int TAP_SINGLE = 3;// 双击手势private static final int TAP_DOUBLE = 4;// 手势处理器private final GestureHandler mHandler;// 手势监听器private final MultiTouchGestureListener mListener;// 双击监听器private MultiTouchDoubleTapListener mDoubleTapListener;// 长按允许阀值private boolean mIsLongpressEnabled;// 速度追踪器private VelocityTracker mVelocityTracker;private class GestureHandler extends Handler {GestureHandler() {super();}GestureHandler(Handler handler) {super(handler.getLooper());}@Overridepublic void handleMessage(Message msg) {int idx = (Integer) msg.obj;switch (msg.what) {case SHOW_PRESS: {if (idx >= sEventInfos.size()) {
//                    Log.w(MYTAG, CLASS_NAME + ":handleMessage, msg.what = SHOW_PRESS, idx=" + idx + ", while sEventInfos.size()="
//                            + sEventInfos.size());break;}EventInfo info = sEventInfos.get(idx);if (info == null) {
//                    Log.e(MYTAG, CLASS_NAME + ":handleMessage, msg.what = SHOW_PRESS, idx=" + idx + ", Info = null");break;}// 触发手势监听器的onShowPress事件mListener.onShowPress(info.mCurrentDownEvent);break;}case LONG_PRESS: {// Log.d(MYTAG, CLASS_NAME + ":trigger LONG_PRESS");if (idx >= sEventInfos.size()) {
//                    Log.w(MYTAG, CLASS_NAME + ":handleMessage, msg.what = LONG_PRESS, idx=" + idx + ", while sEventInfos.size()="
//                            + sEventInfos.size());break;}EventInfo info = sEventInfos.get(idx);if (info == null) {
//                    Log.e(MYTAG, CLASS_NAME + ":handleMessage, msg.what = LONG_PRESS, idx=" + idx + ", Info = null");break;}dispatchLongPress(info, idx);break;}case TAP_SINGLE: {// Log.d(MYTAG, CLASS_NAME + ":trriger TAP_SINGLE");// If the user's finger is still down, do not count it as a tapif (idx >= sEventInfos.size()) {
//                    Log.e(MYTAG, CLASS_NAME + ":handleMessage, msg.what = TAP_SINGLE, idx=" + idx + ", while sEventInfos.size()="
//                            + sEventInfos.size());break;}EventInfo info = sEventInfos.get(idx);if (info == null) {
//                    Log.e(MYTAG, CLASS_NAME + ":handleMessage, msg.what = TAP_SINGLE, idx=" + idx + ", Info = null");break;}if (mDoubleTapListener != null && !info.mStillDown) { //手指在双击超时的阀值内未离开屏幕进行第二次单击事件，则确定单击事件成立（不再触发双击事件）mDoubleTapListener.onSingleTapConfirmed(info.mCurrentDownEvent);}break;}case TAP_DOUBLE: {if (idx >= sEventForDoubleTap.size()) {
//                    Log.w(MYTAG, CLASS_NAME + ":handleMessage, msg.what = TAP_DOUBLE, idx=" + idx + ", while sEventForDoubleTap.size()="
//                            + sEventForDoubleTap.size());break;}EventInfo info = sEventForDoubleTap.get(idx);if (info == null) {
//                    Log.w(MYTAG, CLASS_NAME + ":handleMessage, msg.what = TAP_DOUBLE, idx=" + idx + ", Info = null");break;}sEventForDoubleTap.set(idx, null);// 这个没什么好做的，就是把队列中对应的元素清除而已break;}default:throw new RuntimeException("Unknown message " + msg); // never}}}/*** 触发长按事件* @param info* @param idx*/private void dispatchLongPress(EventInfo info, int idx) {mHandler.removeMessages(TAP_SINGLE, idx);//移除单击事件确认info.mInLongPress = true;mListener.onLongPress(info.mCurrentDownEvent);}/*** 构造器1* @param context* @param listener*/public MultiTouchGestureDetector(Context context, MultiTouchGestureListener listener) {this(context, listener, null);}/*** 构造器2* @param context* @param listener* @param handler*/public MultiTouchGestureDetector(Context context, MultiTouchGestureListener listener, Handler handler) {if (handler != null) {mHandler = new GestureHandler(handler);} else {mHandler = new GestureHandler();}mListener = listener;if (listener instanceof MultiTouchDoubleTapListener) {setOnDoubleTapListener((MultiTouchDoubleTapListener) listener);}init(context);}/*** 初始化识别器* @param context*/private void init(Context context) {if (mListener == null) {throw new NullPointerException("OnGestureListener must not be null");}mIsLongpressEnabled = true;int touchSlop, doubleTapSlop;if (context == null) {touchSlop = ViewConfiguration.getTouchSlop();doubleTapSlop = DOUBLE_TAP_SLAP;mMinimumFlingVelocity = ViewConfiguration.getMinimumFlingVelocity();mMaximumFlingVelocity = ViewConfiguration.getMaximumFlingVelocity();} else {//允许识别器在App中，使用偏好的设定final ViewConfiguration configuration = ViewConfiguration.get(context);touchSlop = configuration.getScaledTouchSlop();doubleTapSlop = configuration.getScaledDoubleTapSlop();mMinimumFlingVelocity = configuration.getScaledMinimumFlingVelocity();mMaximumFlingVelocity = configuration.getScaledMaximumFlingVelocity();}mTouchSlopSquare = touchSlop * touchSlop / 16;mDoubleTapSlopSquare = doubleTapSlop * doubleTapSlop;}/*** 设置双击监听器* @param onDoubleTapListener*/public void setOnDoubleTapListener(MultiTouchDoubleTapListener onDoubleTapListener) {mDoubleTapListener = onDoubleTapListener;}/*** 设置是否允许长按* @param isLongpressEnabled*/public void setIsLongpressEnabled(boolean isLongpressEnabled) {mIsLongpressEnabled = isLongpressEnabled;}/*** 判断是否允许长按* @return*/public boolean isLongpressEnabled() {return mIsLongpressEnabled;}/*** 判断当前事件是否为双击事件* <br/> 通过遍历sEventForDoubleTap来匹配是否存在能够构成双击事件的单击事件* @param e* @return*/private EventInfo checkForDoubleTap(MultiMotionEvent e) {if (sEventForDoubleTap.isEmpty()) {
//            Log.e(MYTAG, CLASS_NAME + ":checkForDoubleTap(), sEventForDoubleTap is empty !");return null;}for (int i = 0; i < sEventForDoubleTap.size(); i++) {EventInfo info = sEventForDoubleTap.get(i);if (info != null && isConsideredDoubleTap(info, e)) {sEventForDoubleTap.set(i, null);// 这个单击事件已经被消耗了，所以置为nullmHandler.removeMessages(TAP_DOUBLE, i);// 移除Handler内的为处理消息return info;}}return null;}/*** 判断当前按下事件是否能和指定的单击事件构成双击事件* * @param info* @param secondDown* @return*/private boolean isConsideredDoubleTap(EventInfo info, MultiMotionEvent secondDown) {if (!info.mAlwaysInBiggerTapRegion) { //如多第一次单击事件有过较大距离的移动，则无法构成双击事件return false;}if (secondDown.getEventTime() - info.mPreviousUpEvent.getEventTime() > DOUBLE_TAP_TIMEOUT) {//如果第一次单击的UP时间和第二次单击的down时间时间间隔大于DOUBLE_TAP_TIMEOUT，也无法构成双击事件return false;}int deltaX = (int) info.mCurrentDownEvent.getX() - (int) secondDown.getX();int deltaY = (int) info.mCurrentDownEvent.getY() - (int) secondDown.getY();return (deltaX * deltaX + deltaY * deltaY < mDoubleTapSlopSquare);//最后判断两次单击事件的距离}/*** 将事件信息放入双击判断队列，并返回序号* * @param info* @return*/private int addIntoTheMinIndex(EventInfo info) {for (int i = 0; i < sEventForDoubleTap.size(); i++) {if (sEventForDoubleTap.get(i) == null) {sEventForDoubleTap.set(i, info);return i;}}sEventForDoubleTap.add(info);return sEventForDoubleTap.size() - 1;}/*** 从事件信息队列中移除指定序号的事件* * @param idx*/private void removeEventFromList(int id) {if (id > sEventInfos.size() || id < 0) {
//            Log.e(MYTAG, CLASS_NAME + ".removeEventFromList(), id=" + id + ", while sEventInfos.size() =" + sEventInfos.size());return;}sEventInfos.set(id, null);}/*** 向事件队列中添加新信息* * @param e*/private void addEventIntoList(EventInfo info) {int id = info.mCurrentDownEvent.getId();if (id < sEventInfos.size()) {
//            if (sEventInfos.get(id) != null)
//                Log.e(MYTAG, CLASS_NAME + ".addEventIntoList, info(" + id + ") has not set to null !");sEventInfos.set(info.mCurrentDownEvent.getId(), info);} else if (id == sEventInfos.size()) {sEventInfos.add(info);} else {
//            Log.e(MYTAG, CLASS_NAME + ".addEventIntoList, invalidata id !");}}public boolean onTouchEvent(MotionEvent ev) {if (mVelocityTracker == null) {mVelocityTracker = VelocityTracker.obtain();}mVelocityTracker.addMovement(ev);//把所有事件都添加到速度追踪器，为计算速度做准备boolean handled = false;final int action = ev.getAction(); //获取Action
//        int idx = (action & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;//获取触摸事件的序号int idx = ev.getPointerId(ev.getActionIndex());//获取触摸事件的idswitch (action & MotionEvent.ACTION_MASK) {case MotionEvent.ACTION_DOWN:case MotionEvent.ACTION_POINTER_DOWN: {EventInfo info = new EventInfo(MotionEvent.obtain(ev));this.addEventIntoList(info);//将手势信息保存到队列中if (mDoubleTapListener != null) {//如果双击监听器不为nullif (mHandler.hasMessages(TAP_DOUBLE)) {MultiMotionEvent e = new MultiMotionEvent(ev);EventInfo origInfo = checkForDoubleTap(e);//检查是否构成双击事件if (origInfo != null) {info.mIsDoubleTapping = true;handled |= mDoubleTapListener.onDoubleTap(origInfo.mCurrentDownEvent);handled |= mDoubleTapListener.onDoubleTapEvent(e);}}if (!info.mIsDoubleTapping) {//当前事件不构成双击事件，那么发送延迟消息以判断onSingleTapConfirmed事件mHandler.sendMessageDelayed(mHandler.obtainMessage(TAP_SINGLE, idx), DOUBLE_TAP_TIMEOUT);// Log.d(MYTAG, CLASS_NAME + ": add TAP_SINGLE");}}// 记录X坐标和Y坐标info.mLastMotionX = info.mCurrentDownEvent.getX();info.mLastMotionY = info.mCurrentDownEvent.getY();if (mIsLongpressEnabled) {//允许长按mHandler.removeMessages(LONG_PRESS, idx);mHandler.sendMessageAtTime(mHandler.obtainMessage(LONG_PRESS, idx), info.mCurrentDownEvent.getEventTime() + TAP_TIMEOUT+ LONGPRESS_TIMEOUT);//延时消息以触发长按手势// Log.d(MYTAG, CLASS_NAME +// ":add LONG_PRESS to handler  for idx " + idx);}mHandler.sendMessageAtTime(mHandler.obtainMessage(SHOW_PRESS, idx), info.mCurrentDownEvent.getEventTime() + TAP_TIMEOUT);// 延时消息，触发showPress手势handled |= mListener.onDown(info.mCurrentDownEvent);//触发onDown（）break;}case MotionEvent.ACTION_UP:case MotionEvent.ACTION_POINTER_UP: {MultiMotionEvent currentUpEvent = new MultiMotionEvent(ev);if (idx >= sEventInfos.size()) {
//                Log.e(MYTAG, CLASS_NAME + ":ACTION_POINTER_UP, idx=" + idx + ", while sEventInfos.size()=" + sEventInfos.size());break;}EventInfo info = sEventInfos.get(currentUpEvent.getId());if (info == null) {
//                Log.e(MYTAG, CLASS_NAME + ":ACTION_POINTER_UP, idx=" + idx + ", Info = null");break;}info.mStillDown = false;if (info.mIsDoubleTapping) { //处于双击状态，则触发onDoubleTapEvent事件handled |= mDoubleTapListener.onDoubleTapEvent(currentUpEvent);} else if (info.mInLongPress) {//处于长按状态mHandler.removeMessages(TAP_SINGLE, idx);//可以无视这行代码info.mInLongPress = false;} else if (info.mAlwaysInTapRegion) {//尚未移动过if (mHandler.hasMessages(TAP_SINGLE, idx)) {//还在双击的时间阀值内，所以要为双击判断做额外处理mHandler.removeMessages(TAP_SINGLE, idx);info.mPreviousUpEvent = new MultiMotionEvent(MotionEvent.obtain(ev));int index = this.addIntoTheMinIndex(info);// 把当前事件放入队列，等待双击的判断mHandler.sendMessageAtTime(mHandler.obtainMessage(TAP_DOUBLE, index), info.mCurrentDownEvent.getEventTime()+ DOUBLE_TAP_TIMEOUT); // 将双击超时判断添加到Handler// Log.d(MYTAG, CLASS_NAME + ": add TAP_DOUBLE");}handled = mListener.onSingleTapUp(currentUpEvent);//触发onSingleTapUp事件} else {// A fling must travel the minimum tap distancefinal VelocityTracker velocityTracker = mVelocityTracker;velocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);//计算1秒钟内的滑动速度//获取X和Y方向的速度final float velocityX = velocityTracker.getXVelocity(idx);final float velocityY = velocityTracker.getYVelocity(idx);// Log.i(MYTAG, CLASS_NAME + ":ACTION_POINTER_UP, idx=" + idx +// ", vx=" + velocityX + ", vy=" + velocityY);// 触发滑动事件if ((Math.abs(velocityY) > mMinimumFlingVelocity) || (Math.abs(velocityX) > mMinimumFlingVelocity)) {handled = mListener.onFling(info.mCurrentDownEvent, currentUpEvent, velocityX, velocityY);}}// Hold the event we obtained above - listeners may have changed the// original.if (action == MotionEvent.ACTION_UP) {    //释放速度追踪器mVelocityTracker.recycle();mVelocityTracker = null;// Log.w(MYTAG, CLASS_NAME +// ":ACTION_POINTER_UP, mVelocityTracker.recycle()");}info.mIsDoubleTapping = false;// Log.d(MYTAG, CLASS_NAME + "remove LONG_PRESS");// 移除showPress和长按消息mHandler.removeMessages(SHOW_PRESS, idx);mHandler.removeMessages(LONG_PRESS, idx);removeEventFromList(currentUpEvent.getId());//手指离开，则从队列中删除手势信息break;}case MotionEvent.ACTION_MOVE:for (int rIdx = 0; rIdx < ev.getPointerCount(); rIdx++) {//因为无法确定当前发生移动的是哪个手指，所以遍历处理所有手指MultiMotionEvent e = new MultiMotionEvent(ev, rIdx);if (e.getId() >= sEventInfos.size()) {
//                    Log.e(MYTAG, CLASS_NAME + ":ACTION_MOVE, idx=" + rIdx + ", while sEventInfos.size()=" + sEventInfos.size());break;}EventInfo info = sEventInfos.get(e.getId());if (info == null) {
//                    Log.e(MYTAG, CLASS_NAME + ":ACTION_MOVE, idx=" + rIdx + ", Info = null");break;}if (info.mInLongPress) {    //长按，则不处理move事件break;}//当前坐标float x = e.getX();float y = e.getY();//距离上次事件移动的位置final float scrollX = x - info.mLastMotionX;final float scrollY = y - info.mLastMotionY;if (info.mIsDoubleTapping) {//双击事件handled |= mDoubleTapListener.onDoubleTapEvent(e);} else if (info.mAlwaysInTapRegion) {//该手势尚未移动过（移动的距离小于mTouchSlopSquare,视为未移动过）// 计算从落下到当前事件，移动的距离final int deltaX = (int) (x - info.mCurrentDownEvent.getX());final int deltaY = (int) (y - info.mCurrentDownEvent.getY());// Log.d(MYTAG, CLASS_NAME + "deltaX="+deltaX+";deltaY=" +// deltaX +"mTouchSlopSquare=" + mTouchSlopSquare);int distance = (deltaX * deltaX) + (deltaY * deltaY);if (distance > mTouchSlopSquare) {     // 移动距离超过mTouchSlopSquarehandled = mListener.onScroll(info.mCurrentDownEvent, e, scrollX, scrollY);info.mLastMotionX = e.getX();info.mLastMotionY = e.getY();info.mAlwaysInTapRegion = false;// Log.d(MYTAG, CLASS_NAME +// ":remove LONG_PRESS for idx" + rIdx +// ",mTouchSlopSquare("+mTouchSlopSquare+"), distance("+distance+")");// 清除onSingleTapConform，showPress,longPress三种消息int id = e.getId();mHandler.removeMessages(TAP_SINGLE, id);mHandler.removeMessages(SHOW_PRESS, id);mHandler.removeMessages(LONG_PRESS, id);}if (distance > mBiggerTouchSlopSquare) {//移动距离大于mBiggerTouchSlopSquare，则无法构成双击事件info.mAlwaysInBiggerTapRegion = false;}} else if ((Math.abs(scrollX) >= 1) || (Math.abs(scrollY) >= 1)) {//之前已经移动过了handled = mListener.onScroll(info.mCurrentDownEvent, e, scrollX, scrollY);info.mLastMotionX = x;info.mLastMotionY = y;}}break;case MotionEvent.ACTION_CANCEL:cancel();//清理}return handled;}// 清理所有队列private void cancel() {mHandler.removeMessages(SHOW_PRESS);mHandler.removeMessages(LONG_PRESS);mHandler.removeMessages(TAP_SINGLE);mVelocityTracker.recycle();mVelocityTracker = null;sEventInfos.clear();sEventForDoubleTap.clear();}}

来自：源码天堂整理