Android-未检测到ACTION_UP

Question

I am unable to figure out why the ACTION_UP event is not being fired when I move my finger away from contact in the following code.

public boolean onTouch(View v, MotionEvent event) {
        switch(event.getActionIndex()){
        case MotionEvent.ACTION_UP:
            Utils.log("Touch Up");
            break;
        case MotionEvent.ACTION_DOWN:
            Utils.log("Touch Down");
            break;
        }
        return true;
    }

Answer 1

You should use getActionMasked() .

• getAction() returns single pointer events (and deprecated multiple pointer events...)
• getActionMasked() returns single and multiple pointer events (use with getActionIndex() to determine which pointer),
• getActionIndex() returns only the pointer index.

So getActionIndex() returns which finger performed a down / up action (0, 1, 2, etc.) While getAction() or getActionMasked() return the single pointer events you want ( ACTION_DOWN , ACTION_UP , etc.)

Answer 2

Replace your code with mine.

public boolean onTouch(View v, MotionEvent event) {
          //Here's the problem            
       switch(event.getAction()){
        case MotionEvent.ACTION_UP:
            Utils.log("Touch Up");
            break;
        case MotionEvent.ACTION_DOWN:
            Utils.log("Touch Down");
            break;
        }
        return true;
    }

Answer 3

For others having a similar problem, one of the reasons why ACTION_UP is not fired could be overly sensitive ACTION_MOVE. In this case, ACTION_UP never gets fired because system interprets touch action as ACTION_MOVE and fires it instead.

A solution for that is to check when ACTION_MOVE happens if x and y offset is big enough to handle it as ACTION_MOVE, otherwise, you can threat it as ACTION_UP. Here is SO example.