I think you need to modify SDLActivity.java to do that : 

public SDLSurface(Context context) {
         super(context);
         getHolder().addCallback(this);
         getHolder().setFormat(PixelFormat.RGBA_8888); // Add this line & set the format there.

Sylvain, shouldn't we be taking the surface format from the desired EGL depth?

Indeed you're right, it seems enough to set:
    SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);


After that, the calls to "eglGetConfigAttrib" and "ANativeWindow_setBuffersGeometry" report and use a "format == 1 ".
(https://hg.libsdl.org/SDL/file/f7abcb63e51e/src/video/SDL_egl.c#l726 ).
Which means WINDOW_FORMAT_RGBA_8888. (see the file android/native_window.h)


But, what is strange is that the SDLActivity java function surfaceChanged would still report RGB_565.
https://developer.android.com/reference/android/view/SurfaceHolder.Callback.html#surfaceChanged(android.view.SurfaceHolder,%20int,%20int,%20int)

(for the first call that could make sense (default value), then egl re-configure the java surface, but after some foreground/background, surfaceChanged still reports RGB_565)




Android ndk:  android/native_window.h

 26 /*
 27  * Pixel formats that a window can use.
 28  */
 29 enum {
 30     WINDOW_FORMAT_RGBA_8888          = 1,
 31     WINDOW_FORMAT_RGBX_8888          = 2,
 32     WINDOW_FORMAT_RGB_565            = 4,
 33 };

 88 /*
 89  * Change the format and size of the window buffers.
 90  *
 91  * The width and height control the number of pixels in the buffers, not the
 92  * dimensions of the window on screen.  If these are different than the
 93  * window's physical size, then it buffer will be scaled to match that size
 94  * when compositing it to the screen.
 95  *
 96  * For all of these parameters, if 0 is supplied then the window's base
 97  * value will come back in force.
 98  *
 99  * width and height must be either both zero or both non-zero.
100  *
101  */
102 int32_t ANativeWindow_setBuffersGeometry(ANativeWindow* window,
103

I have fixed in: https://hg.libsdl.org/SDL/rev/82f9397db3e7

Once you have the EGL format, it calls "Android_JNI_SetSurfaceViewFormat" to reconfigure the java SurfaceView holder format with it.

(Not much difference, but maybe it's the reason for the black screen on some phone ..)

Marked as fixed!

A corner from the patch is fixed here: https://hg.libsdl.org/SDL/rev/bedfecf09e71
Test-case:

Set
    SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);

So that it will trigger a SurfaceView holder reconfiguration after the window is created (eg surfaceDestroyed/Created/Change sequence).

Add a SDL_Delay(500) and start rendering. (This is for the test-case, but it can be considered as loading resources).

- event loop is filled with 

SDL_WINDOWEVENT_ENTER
SDL_WINDOWEVENT_FOCUS_LOST
SDL_WINDOWEVENT_MINIMIZED
SDL_APP_WILL ENTER BACKGROUND
SDL_APP_DID ENTER BACKGROUND
SDL_APP_WILL ENTER FOREGROUND
SDL_APP_DID ENTER FOREGROUND
SDL_WINDOWEVENT_FOCUS_GAINED
SDL_WINDOWEVENT_RESTORED

- The extra surfaceDestroyed/Created/Change is destroying EGL_Surface, Creating a new one, but not doing MakeCurrent.

Application starts polling, and render with no context made current. 
First eglSwapBuffers reports EGL_BAD_SURFACE.

At second polling, it does the pause/resume, hence backup-restore and make current and it renders.

With the patch, backup-restore and make current is done after SDL_APP_DID ENTER BACKGROUND is consumed.

Another corner case: https://hg.libsdl.org/SDL/rev/b5f8e6c420c2

Can be triggered by putting the screen off (manually), as soon as the app starts