OpenGL ES: A Gentle Introduction - Beginning Android Games - page 282

We keep a reference to a GLSurfaceView instance as a member of the class. In the onCreate()
method, we make our application go full-screen, create the GLSurfaceView , set our Renderer
implementation, and make the GLSurfaceView the content view of our activity.
@Override
public void onResume() {
super .onPause();
glView.onResume();
}
@Override
public void onPause() {
super .onPause();
glView.onPause();
}
In the onResume() and onPause() methods, we call the supermethods as well as the respective
GLSurfaceView methods. These will start up and tear down the rendering thread of the
GLSurfaceView , which in turn will trigger the callback methods of our Renderer implementation at
appropriate times.
static class SimpleRenderer implements Renderer {
Random rand = new Random();
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
Log. d ("GLSurfaceViewTest", "surface created");
}
public void onSurfaceChanged(GL10 gl, int width, int height) {
Log. d ("GLSurfaceViewTest", "surface changed: "+width+"x"
+ height);
}
public void onDrawFrame(GL10 gl) {
gl.glClearColor(rand.nextFloat(), rand.nextFloat(),
rand.nextFloat(), 1);
gl.glClear(GL10. GL_COLOR_BUFFER_BIT );
}
}
}
The final piece of the code is our Renderer implementation. It just logs some information in
the onSurfaceCreated() and onSurfaceChanged() methods. The really interesting part is the
onDrawFrame() method.
As stated earlier, the GL10 instance gives us access to the OpenGL ES API. The 10 in GL10
indicates that it offers us all the functions defined in the OpenGL ES 1.0 standard. For now, we
can be happy with that. All the methods of that class map to a corresponding C function, as
defined in the standard. Each method begins with the prefix gl , an old tradition of OpenGL ES.
The first OpenGL ES method we call is glClearColor() . You probably already know what that
will do. It sets the color to be used when we issue a command to clear the screen. Colors in