Android for Game Developers - Beginning Android Games - page 168

import android.view.View;
import android.view.Window;
import android.view.WindowManager;
public class RenderViewTest extends Activity {
class RenderView extends View {
Random rand = new Random();
public RenderView(Context context) {
super (context);
}
protected void onDraw(Canvas canvas) {
canvas.drawRGB(rand.nextInt(256), rand.nextInt(256),
rand.nextInt(256));
invalidate();
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super .onCreate(savedInstanceState);
requestWindowFeature(Window. FEATURE_NO_TITLE );
getWindow().setFlags(WindowManager.LayoutParams. FLAG_FULLSCREEN ,
WindowManager.LayoutParams. FLAG_FULLSCREEN );
setContentView( new RenderView( this ));
}
}
For our first graphics demo, this is pretty concise. We define the RenderView class as an inner class
of the RenderViewTest activity. The RenderView class derives from the View class, as discussed
earlier, and has a mandatory constructor as well as the overridden onDraw() method. It also has an
instance of the Random class as a member; we'll use that to generate our random colors.
The onDraw() method is dead simple. We first tell the Canvas to fill the whole view with a random
color. For each color component, we simply specify a random number between 0 and 255
( Random.nextInt() is exclusive). After that, we tell the system that we want the onDraw() method
to be called again as soon as possible.
The onCreate() method of the activity enables full-screen mode and sets an instance of our
RenderView class as the content view. To keep the example short, we're leaving out the wake
lock for now.
Taking a screenshot of this example is a little bit pointless. All it does is fill the screen with a
random color as fast as the system allows on the UI thread. It's nothing to write home about.
Let's do something more interesting instead: draw some shapes.
Note The preceding method of continuous rendering works, but we strongly recommend not
using it! We should do as little work on the UI thread as possible. In a minute, we'll use a separate
thread to discuss how to do it properly, where later on we can also implement our game logic.