Saturday, October 16, 2010

android touch event summary

In "implement drag and drop on android", I wrote the rules how touch event can be passed to the touched view's parent, and how a parent can intercept the touched view's event. On a device without mouse, Click and LongClicked events are also strongly related to touch event. So, I'll summarize how they are related.

  1. Button widget doesn't bubble event. If a button is touched, it doesn't pass the event to its parent in any case. (There should be more widgets exhibit this character.)
  2. Touch event doesn't bubble up to parent if the widget also registers Click or LongClick event handler.
  3. If a widget registers both Touch and Click event handler, Click event fires only when Touch event handler returns false. In other words, Click event gets fired only when touch event handler declares it's not interested in the touch event.
  4. If a widget registers both Click and LongClick event handler, and LongClick event get fired. Click event will be fired only if LongClick event handler returns false.

Testing Code:

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