how to use multitouch properly - purpose of MotionEvent.getActionIndex()?

Question

MotionEvent's documentation states in Consistency Guarantees that: "(For touch events)... pointers go down one at a time, move around as a group and then go up one at a time or are canceled".

If I understand correctly, there are two ways one can determine the action that triggered onTouchEvent():

• MotionEvent.getAction()
• MotionEvent.getActionMasked() with MotionEvent.getActionIndex() (this should be used for multitouch, which is what I'm after)

Since getActionMasked() always returns just ACTION_POINTER_DOWN and ACTION_POINTER_UP, according to Consistency Guarantees there should always be just one pointer passed inside MotionEvent to onTouchEvent(), which means that MotionEvent.getActionIndex() will always return 0.

If that is so, what is the point of having MotionEvent.getActionIndex() at all? In other words: what am I missing?

UPDATE: To further clarify my question: MotionEvent.getActionMasked() returns just one action and MotionEvent.getActionIndex() tells us which pointer it applies to. Does that mean that we can't get the action for other pointers? Or if it is the same for all pointers, why specify actionIndex at all?

Answer 1

The event ACTION_POINTER_DOWN means two or more fingers are now touching the screen, to distinguish whether it is the second or third (etc) finger you need to use getActionIndex().

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Since getActionMasked() always returns just ACTION_POINTER_DOWN and ACTION_POINTER_UP

In case there is any confusion, getActionMasked() returns many more types like ACTION_DOWN, ACTION_MOVE, etc.