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。