在没有onInterceptTouchEvent的情况下调度ACTION_CANCEL

Question

I am extending View and overriding onTouchEvent.
I want to fire/dispatch MotionEvent.ACTION_CANCEL when the second finger touch the screen. Is there a way to do that?

Answer 1

You can either call or override dispatchTouchEvent(MotionEvent event).

Who do you want to send ACTION_CANCEL to? If your View is a ViewGroup for instance, this would send it to all of its children on the second press:

class MyGroup extends ViewGroup {
    ...
    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        // Is this the second finger down?
        if (event.getActionMasked() == MotionEvent.ACTION_POINTER_DOWN) {
            // Cancel all children
            MotionEvent cancelEvent = MotionEvent.obtain(event);
            cancelEvent.setAction(MotionEvent.ACTION_CANCEL);
            for (int i = 0; i < getChildCount(); i++) {
                View child = getChildAt(i);
                child.dispatchTouchEvent(cancelEvent);
            }
            cancelEvent.recycle();
            return false;
        }
        // Otherwise just do the normal behavior
        return super.dispatchTouchEvent(event);
    }
    ...
}