The only place I can find documentation on OpenGL ES 2.0 for android is at https://developer.android.com/reference/android/opengl/GLES20.html and at the tutorials on their website. Where can I find an api that explains what the GLES20 methods do? The current api just lists them without any explanation. I've run several internet searches and have had no luck.
OpenGL ES is managed by the Khronos Group and documentation can be found on their site here: http://www.khronos.org/opengles/sdk/docs/man/
It may not be Java/Android specific, but it is the 'official' documentation for OpenGL ES 2.0. You could use it in combination with the link you provided yourself for the actual Java/Android calls.
I also had trouble figuring out open GL and the related libraries just from online resources. Eventually I ran across a reference to a book:
OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3 (8th Edition). This is the latest edition of the "Red Book" (even though it is orange).
There are a bunch of books about OpenGL and related libraries, you might have to get some. I haven't got any yet so I can't say which one(s) might be best.
Also, I just googled for gles20, and came across this site.
http://www.learnopengles.com/category/android-tutorials/
Looks like it might be useful.
There are a lot of undocumented pitfalls to using OpenGL ES on Android. I highly recommend starting with example code that is Android specific. This article is a good starting point:
来源：https://stackoverflow.com/questions/17288113/where-is-the-documentation-for-opengl-es-2-0-on-android