You just confirmed that pinch = keycode 7 and stretch = keycode 8, as was reported some time ago:
https://www.mobileread.com/forums/sho....php?p=1932094
You gave good information on how to use this information in java. Perhaps you could try the other gestures reported in that previous thread, using your method.
We have SO MANY threads here, that a lot of useful information can get deeply burried. The gesture engine thread link above IS in the index wikis, but even those wikis are getting a bit large.