Each runtime has its own sample project.
spine-libgdx represents the java implementation and that has a few sample classes. spine-runtimes/spine-libgdx/spine-libgdx-tests/src/com/esotericsoftware/spine at master · EsotericSoftware/spine-runtimes · GitHub
Any other Android-targetable framework, you can check the sample project from the framework folder too.
For example, spine-cocos2dx has a few. spine-unity has several.
Other frameworks/engines probably target Android too.
Each framework/engine runtime also serve as sample implementations of how to hook into the Spine core if you plan to use another engine that we don't have an official runtime for.