Android NDK Beginner`s Guide - Second Edition

Time for action – clearing and swapping buffers

Let's clear the display buffers with a color fading from black to white:

1. While still being in jni/GraphicsManager.cpp, refresh the screen during each update step with eglSwapBuffers().

   To have a visual feedback, change the display background color gradually with the help of glClearColor() before erasing the Framebuffer with glClear():

   ...
   status GraphicsManager::update() {
       static float clearColor = 0.0f;
       clearColor += 0.001f;
       glClearColor(clearColor, clearColor, clearColor, 1.0f);
       glClear(GL_COLOR_BUFFER_BIT);
   
       if (eglSwapBuffers(mDisplay, mSurface) != EGL_TRUE) {
           Log::error("Error %d swapping buffers.", eglGetError());
           return STATUS_KO;
       } else {
           return STATUS_OK;
       }
   }

2. Update the Android.mk file to link ...