使用OnTouchListener()的一个坑,监听不到MotionEvent.ACTION_UP

本文通过实例探讨了Android中OnTouchListener的返回值true与false的区别。指出在单独使用时需返回true以确保ACTION_UP事件被监听;而与setOnClickListener共用时则需返回false,以保证点击事件也能正常触发。

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今天在使用OnTouchListener()的时候遇到了一个坑,下面先贴出代码,再分析这个坑。
  activity_main_image.setOnTouchListener(new View.OnTouchListener() {

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    continueThread = true;
                    progressRun();
                    thread.start();
                    Log.e("Debug", "7");
                }
                if (event.getAction() == MotionEvent.ACTION_UP) {
                    Log.e("Debug", "8");
                    continueThread = false;
                }
                *强调内容***return false**;
            }
        });  

问题出在这里
下面分析下返回false和true的区别:
setOnTouchListener 单独使用的时候返回值需要设置为true,这样才能保证MotionEvent.ACTION_UP的时候能获取相应的监听,而非一次监听(即每次只有一个按下的事件能被监听到)。
当setOnTouchListener 和 setOnClickListener 同时使用时,onTouch 的返回值要设为 false,这样既可以保证按下,然后再抬起的时候可以被监听,并且点击事件也会被监听。

package com.blog.demo11; import android.annotation.SuppressLint; import android.os.Bundle; import android.view.MotionEvent; import android.view.View; import android.widget.ImageView; import androidx.annotation.Nullable; import com.blog.BaseActivity; import com.blog.R; import static android.view.MotionEvent.INVALID_POINTER_ID; /** * 可拖拽效果类。 */ public class ViewDragActivity extends BaseActivity { private ImageView backgroundImage; private ImageView image1; private ImageView image2; @SuppressLint("MissingInflatedId") @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.drag_layout); backgroundImage = findViewById(R.id.background_image); image1 = findViewById(R.id.image1); image2 = findViewById(R.id.image2); // Set touch listeners for each image image1.setOnTouchListener(new MultiTouchListener()); image2.setOnTouchListener(new MultiTouchListener()); } private class MultiTouchListener implements View.OnTouchListener { private float lastTouchX, lastTouchY; private int activePointerId = INVALID_POINTER_ID; @Override public boolean onTouch(View v, MotionEvent event) { switch (event.getActionMasked()) { case MotionEvent.ACTION_DOWN: { final int pointerIndex = event.getActionIndex(); final float x = event.getX(pointerIndex); final float y = event.getY(pointerIndex); lastTouchX = x; lastTouchY = y; activePointerId = event.getPointerId(pointerIndex); break; } case MotionEvent.ACTION_MOVE: { final int pointerIndex = event.findPointerIndex(activePointerId); final float x = event.getX(pointerIndex); final float y = event.getY(pointerIndex); final float dx = x - lastTouchX; final float dy = y - lastTouchY; v.setX(v.getX() + dx); v.setY(v.getY() + dy); lastTouchX = x; lastTouchY = y; break; } case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: { activePointerId = INVALID_POINTER_ID; break; } case MotionEvent.ACTION_POINTER_UP: { final int pointerIndex = event.getActionIndex(); final int pointerId = event.getPointerId(pointerIndex); if (pointerId == activePointerId) { final int newPointerIndex = pointerIndex == 0 ? 1 : 0; lastTouchX = event.getX(newPointerIndex); lastTouchY = event.getY(newPointerIndex); activePointerId = event.getPointerId(newPointerIndex); } break; } } return true; } } }
06-04
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