public class AndroidsCastleActivity extends Activity {

        protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(new MyView(this));
        }

        class MyView extends View {

                public MyView(Context context) {
                        super(context);
                        
                }

                @Override
                protected void onDraw(Canvas canvas) {
                
                        Paint paint = new Paint();
                        paint.setColor(Color.argb(255, 255, 0, 0));//赤セット
                        
                        canvas.drawCircle(50, 50, 50, paint);//円描画
                        
                        //グラデーション情報を作成(0,100)から(240,200)に向けて緑→黄色でグラデーション
                        Shader s = new LinearGradient(0, 100, 240, 200, Color.GREEN, Color.YELLOW,  Shader.TileMode.CLAMP);  
                        paint.setShader(s);//グラデーションをセット 
                        
                        canvas.drawOval(new RectF(0.0f, 100.0f, 240.0f, 200.0f), paint);//楕円描画
                        
                }

        }
}