android_canvas.java

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new MainView(this));
    }

    private class MainView extends View {
        public MainView(Context context) {
            super(context);
        }

        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);

            canvas.drawColor(Color.WHITE);
            Paint paint = new Paint();

            paint.setColor(Color.RED);
            canvas.drawCircle(
                    canvas.getWidth()/2,
                    canvas.getHeight()/4,
                    canvas.getHeight()/10,
                    paint);

            paint.setColor(Color.GREEN);
            paint.setStyle(Paint.Style.STROKE);
            canvas.drawRect(
                    canvas.getWidth()/2 - canvas.getHeight()/10,
                    canvas.getHeight()*2/4 - canvas.getHeight()/10,
                    canvas.getWidth()/2 + canvas.getHeight()/10,
                    canvas.getHeight()*2/4 + canvas.getHeight()/10,
                    paint);

            paint.setColor(Color.BLUE);
            paint.setStyle(Paint.Style.FILL);
            paint.setAntiAlias(true);
            canvas.drawCircle(canvas.getWidth()/2,
                    canvas.getHeight()*3/4,
                    canvas.getHeight()/10,
                    paint);
        }
    }
}