on
Responds to the beginning of a scaling gesture. Reported bynew pointers going down.
Return
Whether or not the detector should continue recognizingthis gesture. For example, if a gesture is beginningwith a focal point outside of a region where it makessense, onScaleBegin() may return false to ignore therest of the gesture.
Parameters
detector
The detector reporting the event - use this toretrieve extended info about event state.