Android系统本身自带了长按事件,setOnLongClickListener即可监听。但是有时候,你不希望使用系统的长按事件,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。
下面的代码定义了一个阈值TOUCH_SLOP,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。
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;
}
}