How to save OpenGL textures when lose context on Android

Question

Our game requires that several large textures are built up dynamically from small images, and we don't keep a data copy of the textures, we just use OpenGL with glTexSubImage2d to update the actual textures.

When Back is pressed, or the game loses focus, we want to save these textures to ram, so if the user then goes back to the game, we can recreate/reload them in onSurfaceCreated. We already reload from 'disk' all static textures.

However, its proving hard to find out where we can get a message to know that we are about to lose the EGL context. If we set a flag in the main activity's onBackPressed then check that flag in the main render loop, we can save the textures there, but we can't access the textures from the main activity, so putting the call in the main activity's onStop callback is too late. There is no subsequent render loop to save the textures, as, well, its stopped by then. We need to do this as there will be other ways where onStop is called other than pressing the Back button.

Supposedly I can't delay onStop to get one more "render" in either. Any other ideas ?

Answer 1

Since you already generate this textures dynamically during the cold start of your application, it may be a good point just to part this textures dirty and regenerate them just as if your application was starting cold.

If you want to save those textures then don't wait for onStop() to be called. Just save them once you have generated their content.