How to distinguish between move and click in onTouchEvent()?

Question

In my application, I need to handle both move and click events.

A click is a sequence of one ACTION_DOWN action, several ACTION_MOVE actions and one ACTION_UP action

Answer 1

I got the best results by taking into account:

1. Primarily, the distance moved between ACTION_DOWN and ACTION_UP events. I wanted to specify the max allowed distance in density-indepenent pixels rather than pixels, to better support different screens. For example, 15 DP.
2. Secondarily, the duration between the events. One second seemed good maximum. (Some people "click" quite "thorougly", i.e. slowly; I still want to recognise that.)

Example:

/**
 * Max allowed duration for a "click", in milliseconds.
 */
private static final int MAX_CLICK_DURATION = 1000;

/**
 * Max allowed distance to move during a "click", in DP.
 */
private static final int MAX_CLICK_DISTANCE = 15;

private long pressStartTime;
private float pressedX;
private float pressedY;

@Override
public boolean onTouchEvent(MotionEvent e) {
     switch (e.getAction()) {
        case MotionEvent.ACTION_DOWN: {
            pressStartTime = System.currentTimeMillis();                
            pressedX = e.getX();
            pressedY = e.getY();
            break;
        }
        case MotionEvent.ACTION_UP: {
            long pressDuration = System.currentTimeMillis() - pressStartTime;
            if (pressDuration < MAX_CLICK_DURATION && distance(pressedX, pressedY, e.getX(), e.getY()) < MAX_CLICK_DISTANCE) {
                // Click event has occurred
            }
        }     
    }
}

private static float distance(float x1, float y1, float x2, float y2) {
    float dx = x1 - x2;
    float dy = y1 - y2;
    float distanceInPx = (float) Math.sqrt(dx * dx + dy * dy);
    return pxToDp(distanceInPx);
}

private static float pxToDp(float px) {
    return px / getResources().getDisplayMetrics().density;
}

The idea here is the same as in Gem's solution, with these differences:

• This calculates the actual Euclidean distance between the two points.
• This uses dp instead of px.

Update (2015): also check out Gabriel's fine-tuned version of this.