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Android自定义长按事件

2010-11-11 21:26:07 作者：chroya 来源：javaeye 浏览次数：1

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。