廢話不多說鲜滩，先看效果。

QQ圖片20170708101103.gif

如何現(xiàn)實(shí)

代碼里面也注釋得很清楚。掃描效果就是通過SweepGradient來實(shí)現(xiàn)的加上變換Matrix來現(xiàn)實(shí)的。

實(shí)現(xiàn)步驟：

1.先實(shí)現(xiàn)圓環(huán)
2.SweepGradient現(xiàn)實(shí)掃描渲染
3.用Matrix旋轉(zhuǎn)變換讓SweepGradient旋轉(zhuǎn)掃描起來

1.先實(shí)現(xiàn)圓環(huán)律杠。很簡單，應(yīng)該不用詳說竞惋。下面就貼代碼柜去。

  //圓圈大小的比例
private float[] circleProportion = {1 / 13f, 2 / 13f, 3 / 13f, 4 / 13f, 5 / 13f, 6 / 13f};

 @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        //圓環(huán)
        drawCircle(canvas);
    }

    private void drawCircle(Canvas canvas) {
        canvas.drawCircle(mWidth / 2, mHeight / 2, maxRadius * circleProportion[0], mPaintCircle);
        canvas.drawCircle(mWidth / 2, mHeight / 2, maxRadius * circleProportion[1], mPaintCircle);
        canvas.drawCircle(mWidth / 2, mHeight / 2, maxRadius * circleProportion[2], mPaintCircle);
        canvas.drawCircle(mWidth / 2, mHeight / 2, maxRadius * circleProportion[3], mPaintCircle);
        canvas.drawCircle(mWidth / 2, mHeight / 2, maxRadius * circleProportion[4], mPaintCircle);
        canvas.drawCircle(mWidth / 2, mHeight / 2, maxRadius * circleProportion[5], mPaintCircle);
    }

效果是：

1.png

2.SweepGradient現(xiàn)實(shí)掃描渲染

不知道SweepGradient可以看一下這篇文章（后面有時(shí)間我也寫一篇，絕對不是我懶拆宛。好吧嗓奢。我承認(rèn)我懶）
http://blog.csdn.net/t12x3456/article/details/10473225

         //初始化掃描渲染
                mSweepGradient = new SweepGradient(mWidth / 2, mHeight / 2, new int[]{Color.TRANSPARENT,
                        Color.parseColor("#84B5CA")}, null);
        
            @Override
            protected void onDraw(Canvas canvas) {
                super.onDraw(canvas);
                //畫一環(huán)環(huán)的圓圈
                drawCircle(canvas);
                //畫掃描
                drawScan(canvas);
            }
    
            private void drawScan(Canvas canvas) {
                //給畫筆設(shè)置渲染效果
                mPaintScan.setShader(mSweepGradient);
                canvas.drawCircle(mWidth / 2, mHeight / 2, maxRadius * circleProportion[4], mPaintScan);
            } 

效果：

2.png

3.用Matrix旋轉(zhuǎn)變換讓SweepGradient旋轉(zhuǎn)掃描起來

不懂Matrix可以看這篇博客：
http://www.gcssloop.com/customview/Matrix_Basic

        Matrix matrix = new Matrix();
        int speed = 5;
        private Runnable run = new Runnable() {
            @Override
            public void run() {
                matrix.preRotate(speed,mWidth/2,mHeight/2);
                invalidate();
                postDelayed(run,130);
            }
        };

    private void drawScan(Canvas canvas) {
        //給畫筆設(shè)置渲染效果
        mPaintScan.setShader(mSweepGradient);
        canvas.concat(matrix);
        canvas.drawCircle(mWidth / 2, mHeight / 2, maxRadius * circleProportion[4], mPaintScan);
    }

具體代碼見：
https://github.com/zsj1225/RadarView

參考：
http://blog.csdn.net/t12x3456/article/details/10473225
http://www.gcssloop.com/customview/Matrix_Basic
http://blog.csdn.net/mr_immortalz/article/details/51319354