More Gaming Tricks with OpenGL and JNI - Pro Android Games - page 71

Listing 3-7 shows a fragment of the GLThread class taken from the GL cubes sample. When
the thread starts, the run() method is invoked, and a semaphore is used to ensure that
guardedRun() can be accessed by one thread only. guardedRun() performs other important
steps, such as the following:

 Initializes the OpenGL ES for a given configuration specification.

The configuration specification defines information, such as pixel
format and image depth.

 Creates the OpenGL surface and tells the renderer about it.

 Checks whether the size of the surface has changed and tells the

renderer about it.

 Queues and gets events to be run on the GL rendering thread.

Listing 3-7. Rendering Thread for the GL Cubes Sample

package opengl.scenes;

// ...

/**
* A generic GL Thread. Takes care of initializing EGL and GL.
* Delegates to a Renderer instance to do the actual drawing.
*/
public class GLThread extends Thread
{
public GLThread(Renderer renderer, SurfaceHolder holder) {
super();
mDone = false;
mWidth = 0;
mHeight = 0;
mRenderer = renderer;
mHolder = holder;
setName("GLThread");
}

@Override
public void run() {
try {
try {
sEglSemaphore.acquire();
} catch (InterruptedException e) {
return;
}
guardedRun();
} catch (Exception ex) {
ex.printStackTrace();
} finally {
sEglSemaphore.release();
}
}