It’s difficult to get Java widgets to work on Android. Here is one alternative:
https://discourse.processing.org/t/androidwidgetcollection/38889
A more historical version is here:
https://github.com/EmmanuelPil/Android-java-code-utilities-widgets-for-Processing-for-Android
And you can roll your own fairly easily if you are so inclined. eg its not too difficult to create your own Button class which is just a rectangle that you trap a click(touch) on.