拖动时停止 OnLongClickListener 触发

Posted 2023-04-18

【中文标题】拖动时停止 OnLongClickListener 触发

【英文标题】：Stop OnLongClickListener from firing while dragging

【发布时间】：2011-09-10 11:21:34

【问题描述】：

我有一个用户可以拖动的带有位图的自定义视图。

我想这样做，所以当他们长按其中一个时，我可以弹出一个上下文菜单，其中包含重置位置等选项。

在自定义视图中，我添加了我的 OnLongClickListener：

this.setOnLongClickListener(new View.OnLongClickListener() 
    @Override
    public boolean onLongClick(View v) 
        // show context menu..
        return true;
    
);

并覆盖 onTouchEvent 看起来像这样：

public boolean onTouchEvent(MotionEvent event) 
    handleDrag(event);
    super.onTouchEvent(event);
    return true;

handleDrag 函数查找被按下的对象，并处理更新它的位置。

我的问题是，当我开始拖动图像时，OnLongClickListener 也会触发。我不确定解决这个问题的最佳方法。

我尝试向 handleDrag 添加一个阈值，以便在用户触地但不尝试拖动时返回 false，但我发现仍然很难触发正确的处理程序。

谁能建议一种在拖动时跳过 OnLongClickListener 的方法？

【参考方案1】：

我想我已经通过调整阈值方法解决了这个问题。

首先，我将 onTouchEvent 更改为如下所示：

 public boolean onTouchEvent(MotionEvent event) 
     mMultiTouchController.handleDrag(event);
     return super.onTouchEvent(event);
 

它们现在都触发了，所以我将 OnLongClickListener 更改为以下内容：

 this.setOnLongClickListener(new View.OnLongClickListener() 
     @Override
     public boolean onLongClick(View v) 
         if (!mMultiTouchController.has_moved) 
             // Pop menu and done...
             return false;
         
         return true;
     
 );

（mMultiTouchController 是包含我所有手势检测代码的类）。 这里的关键是在这个类中，我添加了 bool 'has_moved'。当我开始拖动时，我会计算增量：

 float diffX = Math.abs(mCurrPtX - mPrevPt.getX());
 float diffY = Math.abs(mCurrPtY - mPrevPt.getY());
 if (diffX < threshold && diffY < threshold) 
     has_moved = false;
     return;
 

现在，当 onLongClick 触发时，我知道是否要采取行动。

最后一块是设置：

setHapticFeedbackEnabled(false);

在我的视图中，这样用户就不会在每次 longClick 触发但不采取任何操作时都得到振动。我计划下一步手动进行振动。

到目前为止，这似乎还可以，希望对遇到与此类似情况的任何人有所帮助。

【参考方案2】：

我会停止使用 onLongClickListener 并只实现你自己的，这很容易做到。然后您就拥有了防止它们相互干扰所需的控制权。

以下代码实现了以下手势：拖动、点击、双击、长按和捏合。

static final short NONE = 0;
static final short DRAG = 1;
static final short ZOOM = 2;
static final short TAP = 3;
static final short DOUBLE_TAP = 4;
static final short POST_GESTURE = 5;
short mode = NONE;
static final float MIN_PINCH_DISTANCE = 30f;
static final float MIN_DRAG_DISTANCE = 5f;
static final float DOUBLE_TAP_MAX_DISTANCE = 30f;
static final long MAX_DOUBLE_TAP_MS = 1000;
static final long LONG_PRESS_THRESHOLD_MS = 2000;

public class Vector2d 
    public float x;
    public float y;

    public Vector2d() 
        x = 0f;
        y = 0f;
    

    public void set(float newX, float newY) 
        x = newX;
        y = newY;
    

    public Vector2d avgVector(Vector2d remote) 
        Vector2d mid = new Vector2d();
        mid.set((remote.x + x)/2, (remote.y + y)/2);
        return mid;
    

    public float length() 
        return (float) Math.sqrt(x * x + y * y);
    

    public float distance(Vector2d remote) 
        float deltaX = remote.x - x;
        float deltaY = remote.y - y;
        return (float) Math.sqrt(deltaX * deltaX + deltaY * deltaY);
    


private Vector2d finger1 = new Vector2d();
private Vector2d finger2 = new Vector2d();
private Vector2d pinchStartDistance = new Vector2d();
private Vector2d pinchMidPoint;
private Vector2d fingerStartPoint = new Vector2d();
private long gestureStartTime;
private Marker selectedMarker;

@Override
public boolean onTouch(View v, MotionEvent event) 
    // Dump touch event to log
    dumpEvent(event);

    // Handle touch events here...
    switch (event.getAction() & MotionEvent.ACTION_MASK) 
    case MotionEvent.ACTION_DOWN:
        finger1.set(event.getX(), event.getY());
        if (mode == TAP) 
            if (finger1.distance(fingerStartPoint) < DOUBLE_TAP_MAX_DISTANCE) 
                mode = DOUBLE_TAP;
             else 
                mode = NONE;
                gestureStartTime = SystemClock.uptimeMillis();
            
         else 
            gestureStartTime = SystemClock.uptimeMillis();
        
        fingerStartPoint.set(event.getX(), event.getY());
        break;
    case MotionEvent.ACTION_POINTER_DOWN:
        finger2.set(event.getX(1), event.getY(1));

        pinchStartDistance.set(Math.abs(finger1.x - finger2.x), Math.abs(finger1.y - finger2.y));
        Log.d(TAG, String.format("pinch start distance = %f, %f", pinchStartDistance.x, pinchStartDistance.y));
        if (pinchStartDistance.length() > MIN_PINCH_DISTANCE) 
            if (pinchStartDistance.x < MIN_PINCH_DISTANCE) 
                pinchStartDistance.x = MIN_PINCH_DISTANCE;
            
            if (pinchStartDistance.y < MIN_PINCH_DISTANCE) 
                pinchStartDistance.y = MIN_PINCH_DISTANCE;
            
            pinchMidPoint = finger1.avgVector(finger2);
            mode = ZOOM;
            Log.d(TAG, "mode=ZOOM" );
        
        break;
    case MotionEvent.ACTION_UP:
    case MotionEvent.ACTION_POINTER_UP:
        if (mode == ZOOM) 
            Vector2d pinchEndDistance = new Vector2d();
            pinchEndDistance.set(Math.abs(finger1.x - finger2.x), Math.abs(finger1.y - finger2.y));
            if (pinchEndDistance.x < MIN_PINCH_DISTANCE) 
                pinchEndDistance.x = MIN_PINCH_DISTANCE;
            
            if (pinchEndDistance.y < MIN_PINCH_DISTANCE) 
                pinchEndDistance.y = MIN_PINCH_DISTANCE;
            
            Log.d(TAG, String.format("pinch end distance = %f, %f", pinchEndDistance.x, pinchEndDistance.y));
            zoom(pinchMidPoint, pinchStartDistance.x/pinchEndDistance.x, pinchStartDistance.y/pinchEndDistance.y);
            // Set mode to "POST_GESTURE" so that when the other finger lifts the handler won't think it was a
            // tap or something.
            mode = POST_GESTURE;
         else if (mode == NONE) 
            // The finger wasn't moved enough for it to be considered a "drag", so it is either a tap
            // or a "long press", depending on how long it was down.
            if ((SystemClock.uptimeMillis() - gestureStartTime) < LONG_PRESS_THRESHOLD_MS) 
                Log.d(TAG, "mode=TAP");
                mode = TAP;
                selectedMarker = checkForMarker(finger1);
                if (selectedMarker != null) 
                    Log.d(TAG, "Selected marker, mode=NONE");
                    mode = NONE;
                    ((Activity) parent).showDialog(ResultsActivity.DIALOG_MARKER_ID);
                
            
            else 
                Log.d(TAG, "mode=LONG_PRESS");
                addMarker(finger1);
                requestRender();
            
         else if (mode == DOUBLE_TAP && (SystemClock.uptimeMillis() - gestureStartTime) < MAX_DOUBLE_TAP_MS) 
            // The finger was again not moved enough for it to be considered a "drag", so it is
            // a double-tap.  Change the center point and zoom in.
            Log.d(TAG, "mode=DOUBLE_TAP");
            zoom(fingerStartPoint, 0.5f, 0.5f);
            mode = NONE;
         else 
            mode = NONE;
            Log.d(TAG, "mode=NONE" );
        
        break;
    case MotionEvent.ACTION_MOVE:
        if (mode == NONE || mode == TAP || mode == DOUBLE_TAP) 
            finger1.set(event.getX(), event.getY());
            if (finger1.distance(fingerStartPoint) > MIN_DRAG_DISTANCE) 
                Log.d(TAG, "mode=DRAG" );
                mode = DRAG;
                scroll(fingerStartPoint.x - finger1.x, fingerStartPoint.y - finger1.y);
            
        
        else if (mode == DRAG) 
            scroll(finger1.x - event.getX(), finger1.y - event.getY());
            finger1.set(event.getX(), event.getY());
        
        else if (mode == ZOOM) 
            for (int i=0; i<event.getPointerCount(); i++) 
                if (event.getPointerId(i) == 0) 
                    finger1.set(event.getX(i), event.getY(i));
                
                else if (event.getPointerId(i) == 1) 
                    finger2.set(event.getX(i), event.getY(i));
                
                else 
                    Log.w(TAG, String.format("Unknown motion event pointer id: %d", event.getPointerId(i)));
                
            
        
        break;
    

    return true;


/** Show an event in the LogCat view, for debugging */
private void dumpEvent(MotionEvent event) 
   String names[] =  "DOWN" , "UP" , "MOVE" , "CANCEL" , "OUTSIDE" ,
      "POINTER_DOWN" , "POINTER_UP" , "7?" , "8?" , "9?" ;
   StringBuilder sb = new StringBuilder();
   int action = event.getAction();
   int actionCode = action & MotionEvent.ACTION_MASK;
   sb.append("event ACTION_" ).append(names[actionCode]);
   if (actionCode == MotionEvent.ACTION_POINTER_DOWN
         || actionCode == MotionEvent.ACTION_POINTER_UP) 
      sb.append("(pid " ).append(
      action >> MotionEvent.ACTION_POINTER_ID_SHIFT);
      sb.append(")" );
   
   sb.append("[" );
   for (int i = 0; i < event.getPointerCount(); i++) 
      sb.append("#" ).append(i);
      sb.append("(pid " ).append(event.getPointerId(i));
      sb.append(")=" ).append((int) event.getX(i));
      sb.append("," ).append((int) event.getY(i));
      if (i + 1 < event.getPointerCount())
         sb.append(";" );
   
   sb.append("]" );
   Log.d(TAG, sb.toString());

【参考方案3】：

//此代码用于处理手势检测

final Handler handler = new Handler();
private Runnable mLongPressRunnable;

detector = new GestureDetector(this, new MyGestureDectector());
view.setOnTouchListener(new OnTouchListener() 

        @SuppressLint("ClickableViewAccessibility")
        @SuppressWarnings("deprecation")
        @Override
        public boolean onTouch(View v, MotionEvent event) 
            detector.onTouchEvent(event);
            if (event.getAction() == MotionEvent.ACTION_DOWN) 

                handler.postDelayed(mLongPressRunnable, 1000);
            
            if ((event.getAction() == MotionEvent.ACTION_MOVE)
                    || (event.getAction() == MotionEvent.ACTION_UP)) 
                handler.removeCallbacks(mLongPressRunnable);

                

            

            return true;
        
    );
mLongPressRunnable = new Runnable() 
        public void run() 
            Toast.makeText(MainActivity.this, "long", Toast.LENGTH_SHORT)
                    .show();
        
    ;
class MyGestureDectector implements GestureDetector.OnDoubleTapListener,
        OnGestureListener 
        //Implement all the methods
        

【讨论】：

注意：我发现至少在一台设备上，移动事件几乎在向下事件之后立即触发，即使我尝试完全不移动手指。因此，我建议不要在收到移动事件后立即取消长按（removeCallbacks 实际上是取消）。相反，对 ACCEPTED 答案中显示的“移动阈值”方法进行一些变化。这个答案的handler postDelayed/removeCallbacks 方法可以适应这样的移动阈值。