安卓 自定义View 转圈圈

public class MyView extends View {
    //默认大小
    private int dsize;
    //绘制扇形区域
    private RectF rectF;
    //画笔
    private Paint paint;
    //中心点
    private PointF pointF;
    private int n;
    private int o;

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

    public MyView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        initView();
    }


    private void initView() {
        dsize = 200;
        o = 20;
        rectF = new RectF();
        pointF = new PointF();
        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setStrokeWidth(o);
        paint.setStrokeCap(Paint.Cap.ROUND);
        paint.setColor(Color.BLUE);
        //描边
        paint.setStyle(Paint.Style.STROKE);
    }

    //大小发生变化  第一次绘制
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        //计算区域
        rectF.top = o >> 1;
        rectF.bottom = h - (o >> 1);
        rectF.left =  o >> 1;
        rectF.right = w - (o >> 1);
        //计算中心点
        pointF.y = w >> 1;
        pointF.x = h >> 1;
    }

    //绘制
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.save();
        canvas.rotate(135,pointF.x,pointF.y);
        canvas.drawArc(rectF,0,n,false,paint);
        canvas.restore();
        if (n < 360){
            n += 10;
            postInvalidateDelayed(50);
        }
    }
}