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.RED);//赤に設定する
                        paint.setStrokeWidth(12);//大きさを12にする
                        canvas.drawPoint( 50, 100, paint );
                }

        }
}