Android自定义长按事件

Android系统自带了长按事件，setOnLongClickListener即可监听。但是有时候，你不希望用系统的长按事件，比如当希望长按的时间更长一点的时候。这时候就需要自己来定义这个长按事件了。

    下面是去年我写代码的时候，自定义长按事件的方式：

package chroya.fun;   
  
import android.content.Context;   
import android.view.MotionEvent;   
import android.view.View;   
import android.view.ViewConfiguration;   
  
public class LongPressView1 extends View{   
    private int mLastMotionX, mLastMotionY;   
    //是否移动了   
    private boolean isMoved;   
    //是否释放了   
    private boolean isReleased;   
    //计数器，防止多次点击导致最后一次形成longpress的时间变短   
    private int mCounter;   
    //长按的runnable   
    private Runnable mLongPressRunnable;   
    //移动的阈值   
    private static final int TOUCH_SLOP = 20;   
  
    public LongPressView1(Context context) {   
        super(context);   
        mLongPressRunnable = new Runnable() {   
               
            @Override  
            public void run() {   
                mCounter--;   
                //计数器大于0，说明当前执行的Runnable不是最后一次down产生的。   
                if(mCounter>0 || isReleased || isMoved) return;   
                performLongClick();   
            }   
        };   
    }   
  
    public boolean dispatchTouchEvent(MotionEvent event) {   
        int x = (int) event.getX();   
        int y = (int) event.getY();   
           
        switch(event.getAction()) {   
        case MotionEvent.ACTION_DOWN:   
            mLastMotionX = x;   
            mLastMotionY = y;   
            mCounter++;   
            isReleased = false;   
            isMoved = false;   
            postDelayed(mLongPressRunnable, ViewConfiguration.getLongPressTimeout());   
            break;   
        case MotionEvent.ACTION_MOVE:   
            if(isMoved) break;   
            if(Math.abs(mLastMotionX-x) > TOUCH_SLOP    
                    || Math.abs(mLastMotionY-y) > TOUCH_SLOP) {   
                //移动超过阈值，则表示移动了   
                isMoved = true;   
            }   
            break;   
        case MotionEvent.ACTION_UP:   
            //释放了   
            isReleased = true;   
            break;   
        }   
        return true;   
    }   
} 

package chroya.fun;

import android.content.Context;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;

public class LongPressView1 extends View{
 private int mLastMotionX, mLastMotionY;
 //是否移动了
 private boolean isMoved;
 //是否释放了
 private boolean isReleased;
 //计数器，防止多次点击导致最后一次形成longpress的时间变短
 private int mCounter;
 //长按的runnable
 private Runnable mLongPressRunnable;
 //移动的阈值
 private static final int TOUCH_SLOP = 20;

 public LongPressView1(Context context) {
  super(context);
  mLongPressRunnable = new Runnable() {
   
   @Override
   public void run() {
    mCounter--;
    //计数器大于0，说明当前执行的Runnable不是最后一次down产生的。
    if(mCounter>0 || isReleased || isMoved) return;
    performLongClick();
   }
  };
 }

 public boolean dispatchTouchEvent(MotionEvent event) {
  int x = (int) event.getX();
  int y = (int) event.getY();
  
  switch(event.getAction()) {
  case MotionEvent.ACTION_DOWN:
   mLastMotionX = x;
   mLastMotionY = y;
   mCounter++;
   isReleased = false;
   isMoved = false;
   postDelayed(mLongPressRunnable, ViewConfiguration.getLongPressTimeout());
   break;
  case MotionEvent.ACTION_MOVE:
   if(isMoved) break;
   if(Math.abs(mLastMotionX-x) > TOUCH_SLOP 
     || Math.abs(mLastMotionY-y) > TOUCH_SLOP) {
    //移动超过阈值，则表示移动了
    isMoved = true;
   }
   break;
  case MotionEvent.ACTION_UP:
   //释放了
   isReleased = true;
   break;
  }
  return true;
 }
}
     代码里注释的比较清楚。主要思路是在down的时候，让一个Runnable一段时间后执行，如果时间到了，没有移动超过定义的阈值，也没有释放，则触发长按事件。在真实环境中，当长按触发之后，还需要将后来的move和up事件屏蔽掉。此处是示例，就略去了。

      下面讲讲第二种方式：

package chroya.fun;   
  
import android.content.Context;   
import android.view.MotionEvent;   
import android.view.View;   
import android.view.ViewConfiguration;   
  
public class LongPressView2 extends View{   
    private int mLastMotionX, mLastMotionY;   
    //是否移动了   
    private boolean isMoved;   
    //长按的runnable   
    private Runnable mLongPressRunnable;   
    //移动的阈值   
    private static final int TOUCH_SLOP = 20;   
  
    public LongPressView2(Context context) {   
        super(context);   
        mLongPressRunnable = new Runnable() {   
               
            @Override  
            public void run() {                
                performLongClick();   
            }   
        };   
    }   
  
    public boolean dispatchTouchEvent(MotionEvent event) {   
        int x = (int) event.getX();   
        int y = (int) event.getY();   
           
        switch(event.getAction()) {   
        case MotionEvent.ACTION_DOWN:   
            mLastMotionX = x;   
            mLastMotionY = y;   
            isMoved = false;   
            postDelayed(mLongPressRunnable, ViewConfiguration.getLongPressTimeout());   
            break;   
        case MotionEvent.ACTION_MOVE:   
            if(isMoved) break;   
            if(Math.abs(mLastMotionX-x) > TOUCH_SLOP    
                    || Math.abs(mLastMotionY-y) > TOUCH_SLOP) {   
                //移动超过阈值，则表示移动了   
                isMoved = true;   
                removeCallbacks(mLongPressRunnable);   
            }   
            break;   
        case MotionEvent.ACTION_UP:   
            //释放了   
            removeCallbacks(mLongPressRunnable);   
            break;   
        }   
        return true;   
    }   
} 

package chroya.fun;

import android.content.Context;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;

public class LongPressView2 extends View{
 private int mLastMotionX, mLastMotionY;
 //是否移动了
 private boolean isMoved;
 //长按的runnable
 private Runnable mLongPressRunnable;
 //移动的阈值
 private static final int TOUCH_SLOP = 20;

 public LongPressView2(Context context) {
  super(context);
  mLongPressRunnable = new Runnable() {
   
   @Override
   public void run() {    
    performLongClick();
   }
  };
 }

 public boolean dispatchTouchEvent(MotionEvent event) {
  int x = (int) event.getX();
  int y = (int) event.getY();
  
  switch(event.getAction()) {
  case MotionEvent.ACTION_DOWN:
   mLastMotionX = x;
   mLastMotionY = y;
   isMoved = false;
   postDelayed(mLongPressRunnable, ViewConfiguration.getLongPressTimeout());
   break;
  case MotionEvent.ACTION_MOVE:
   if(isMoved) break;
   if(Math.abs(mLastMotionX-x) > TOUCH_SLOP 
     || Math.abs(mLastMotionY-y) > TOUCH_SLOP) {
    //移动超过阈值，则表示移动了
    isMoved = true;
    removeCallbacks(mLongPressRunnable);
   }
   break;
  case MotionEvent.ACTION_UP:
   //释放了
   removeCallbacks(mLongPressRunnable);
   break;
  }
  return true;
 }
}
     思路跟第一种差不多，不过，在移动超过阈值和释放之后，会将Runnable从事件队列中remove掉，长按事件也就不会再触发了。源码中实现长按的原理也基本如此。