Stop OnLongClickListener from firing while dragging

Question

I have a custom View with bitmaps on it that the user can drag about.

I want to make it so when they long click one of them I can pop up a context menu with options such as reset position etc.

In the custom View I add my OnLongClickListener:

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

And override onTouchEvent to look something like this:

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

The handleDrag function finds what object is been pressed, and handles updating it's position.

My problem is that when I start to drag an image the OnLongClickListener fires also. I'm not sure the best way around this.

I've tried adding a threshold to handleDrag to return false if user touches down but doesn't attempt to drag, but I'm finding it still difficult to get the correct handler fired.

Can anyone suggest a way to skip the OnLongClickListener while dragging?

Answer 1

I think I have this solved through tweaking my threshold approach.

First, I changed my onTouchEvent to look like this:

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

They now both fire, so I then changed my OnLongClickListener to the following:

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

(mMultiTouchController is the class containing all my gesture detection code). The key here is within this class, I added the bool 'has_moved'. When I go to start a drag I then compute the delta:

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

Now when the onLongClick fires I know whether to take action or not.

The final piece was to set:

setHapticFeedbackEnabled(false);

in my View so that the user doesn't get a vibrate every time the longClick fires but no action is taken. I plan to do the vibration manually as a next step.

This seems to be ok so far, hope that helps anyone who has come across a similar situation as this one.

Answer 2

I would stop using the onLongClickListener and just implement your own, which is pretty easy to do. Then you have the control you need to keep them from interfering with each other.

The following code implements the following gestures: drag, tap, double tap, long click, and pinch.

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());
}