Can' get rendering to work(android,SurfaceView,ndk,ANativeWindow)

Question

I searched the whole day and can still not figure out, what I am missing. All Examples I found are either incomplete (only not connected snippets) or overcomplete(cannt see what is really part if the principle)

I have an Activity that has a View that extends SurfaceView that should be filled using a native method. It is currently implemented by a memset(..,0,..) but my View is white although all calls seem fine.

MyView:

public class MyView extends SurfaceView implements SurfaceHolder.Callback
{
  public MyView(Context context)
  {
    super(context);
    SurfaceHolder sh = getHolder();
    sh.addCallback(this);
  }

  // protected void onDraw(Canvas canvas) // works to make the view red
  //   { canvas.drawColor(Color.RED);} 

  public void surfaceChanged(SurfaceHolder holder, int format, int width, int height)
  {
    nativeRender(holder.getSurface(), width, height);
  }

  public void surfaceCreated(SurfaceHolder holder)
  {}

  public void surfaceDestroyed(SurfaceHolder holder)
  {}

  private native void nativeRender(Object surface, int width, int height);
}

Native method:

void ...nativeRender(JNIEnv* env, jobject myView, jobject surface, jint width, jint height)
{
   ANativeWindow* pWindow(ANativeWindow_fromSurface(env, surface));
   ANativeWindow_setBuffersGeometry(pWindow, width,height,WINDOW_FORMAT_RGBX_8888);

   ANativeWindow_Buffer buffer;

   if (ANativeWindow_lock(pWindow, &buffer, NULL) == 0) 
   {
       memset(buffer.bits, 0, buffer.stride*buffer.height*4);
       ANativeWindow_unlockAndPost(pWindow);
   }
   ANativeWindow_release(pWindow);
}

Things I checked:

• return values of all ANativeWindow_* are 0.
• buffer size/format is as expected

Things I tried:

• calling nativeRender() from onDraw()
• calling nativeRender() repeatetly (Handler(mainLooper(), postDelayed())
• keeping ANativeWindow* as static variable (over multiple calls of the above)
• same without the ANativeWindow_release(pWindow);
• WINDOW_FORMAT_RGBX_8888 vs WINDOW_FORMAT_RGBA_8888
• fill with patterns

So it looks to me that I fill a buffer of the correct dimensions that is never shown. Probably I' missing something obvious because nobody else seems to have problems in that way.

Thanks in Advance Moritz

Answer 1

Thanks!

fadden's comment was the answer. My code actually called setBackgroundColor() which is obviously not what I wanted...

(Although I would expect that in this context this property would have no meaning or would be what the buffer would be prefilled with...)