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。