Android OnTouch MotionEvent 动作

Question

So I think I have a very simple issue but I can't seem to figure it out.

I have an ImageView and I am using it's setOnTouchListener method ( OnTouch ).

How can I differentiate between the ACTION_DOWN event and ACTION_MOVE event?

Even when I just click (touch) on the ImageView , ACTION_MOVE event gets called.

My goal is to open something(do anything) when the user clicks on it and move it when user holds it and moves it.

private int initialX;
private int initialY;
private float initialTouchX;
private float initialTouchY;

@Override
public boolean onTouch(View v, MotionEvent event) {
    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            initialX = params.x;
            initialY = params.y;
            initialTouchX = event.getRawX();
            initialTouchY = event.getRawY();
            return true;
       case MotionEvent.ACTION_UP:
           return true;
       case MotionEvent.ACTION_MOVE:
           params.x = initialX + (int) (event.getRawX() - initialTouchX);
           params.y = initialY + (int) (event.getRawY() - initialTouchY);
           mWindowManager.updateViewLayout(mImgFloatingView, params);

           // Log.d("Params", "X: " + params.x + ".  Y: " + params.y + ".");

          if(params.x == initialX && params.y == initialY) {
              Toast.makeText(getBaseContext(), "Test", Toast.LENGTH_SHORT).show();
          }

          return true;
      }
      return false;
}

Answer 1

As others have said, ACTION_MOVE is called along with ACTION_DOWN because of the sensitivity of the device and the inherent unsensitivity of big fingers. This is known as touch slop . The results you want can be obtained by adjusting the thresholds for time and distance moved. Alternatively, you could use a gesture detector .

OnTouch MotionEvent Actions

Based on the title of the question, I came here looking for a quick reference for the onTouch MotionEvent actions. So here is a snippet copied from the documentation :

@Override
public boolean onTouchEvent(MotionEvent event){

    int action = event.getActionMasked();

    switch(action) {
        case (MotionEvent.ACTION_DOWN) :
            Log.d(DEBUG_TAG,"Action was DOWN");
            return true;
        case (MotionEvent.ACTION_MOVE) :
            Log.d(DEBUG_TAG,"Action was MOVE");
            return true;
        case (MotionEvent.ACTION_UP) :
            Log.d(DEBUG_TAG,"Action was UP");
            return true;
        case (MotionEvent.ACTION_CANCEL) :
            Log.d(DEBUG_TAG,"Action was CANCEL");
            return true;
        case (MotionEvent.ACTION_OUTSIDE) :
            Log.d(DEBUG_TAG,"Movement occurred outside bounds " +
                    "of current screen element");
            return true;
        default :
            return super.onTouchEvent(event);
    }
}

Notes:

• The above code could be used in an activity or a subclassed view. If subclassing a view is not desired, then the same motion events can be tracked by adding an OnTouchListener to the view. (example also taken from the documentation )

   View myView = findViewById(R.id.my_view); myView.setOnTouchListener(new OnTouchListener() { public boolean onTouch(View v, MotionEvent event) { // ... Respond to touch events return true; } });

• Difference between getAction() and getActionMasked()

• Returning true means that future events will still be processed. So if you returned false for ACTION_DOWN then all other events (like move or up) would be ignored.

Further reading

• Using Touch Gestures : This is a series of official lessons in the documentation. It is an essential read for understanding how to correctly handle touch events and gestures.

Answer 2

What is happening is that View.OnTouchListener will send you ALL events. If you tap and move by only 1 pixel, it'll be registered as a ACTION_MOVE.

You will need to implement some logic to determine a 'hold' action - waiting 100ms or something similar - after which a 'drag' action can proceed. Before that time, it should just be a 'click' action.