1、效果图

雷达.gif

2、自定义的View

public class View_07 extends View {
    private Paint mPaint;
    private static float[] circleProportion = {1 / 15f, 2 / 15f, 3 / 15f, 4 / 15f, 5 / 15f, 6 / 15f};
    private Bitmap bitmap;

    private Paint mPaintScan;//扫描的画笔
    private Matrix matrix = new Matrix();// 旋转需要的矩阵
    private int mRoteDegree;//扫描的角度
    private Shader scanShader;

    private static final String TAG = "View_07";
    public View_07(Context context) {
        this(context, null);
    }

    public View_07(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public View_07(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mPaint = new Paint();
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(2);
        mPaint.setColor(Color.WHITE);
        mPaint.setAntiAlias(true);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int mWidth = MeasureSpec.getSize(widthMeasureSpec);
        int mHeight = MeasureSpec.getSize(heightMeasureSpec);
        setMeasuredDimension(mWidth, mHeight);
        //设置扫描渲染的shader
        scanShader = new SweepGradient(mWidth / 2, mHeight / 2,
                new int[]{Color.TRANSPARENT, Color.parseColor("#84B5CA")}, null);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int x = getWidth() / 2;
        int y = getHeight() / 2;

       //画⚪
        for (int i = 0; i < circleProportion.length; i++) {
            canvas.drawCircle(x, y, getWidth() * circleProportion[i], mPaint);
        }
        bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.foucs);
        canvas.drawBitmap(bitmap, x - bitmap.getWidth() / 2, y - bitmap.getHeight() / 2, mPaint);
        drawSweep(canvas, x, y, (int)(getWidth() * circleProportion[circleProportion.length-1]));

//        LinearGradient 线性渐变
//        shader=new LinearGradient(300,300,400,400, Color.RED, Color.BLUE
//                , Shader.TileMode.CLAMP);

//        RadialGradient 辐射渐变
//         shader = new RadialGradient(300, 300, 200, Color.RED, Color.BLUE, Shader.TileMode.CLAMP);

//        SweepGradient 扫描渐变
//        shader=new SweepGradient(300,300,Color.RED, Color.BLUE);

//        BitmapShader
//        Bitmap bitmap=BitmapFactory.decodeResource(getResources(),R.mipmap.ic_launcher);
//        shader=new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);


    }


    /**
     * 画扫描效果
     */
    private void drawSweep(Canvas canvas, int cx, int cy, int radius) {
        //扇形的透明的渐变效果
        SweepGradient sweepGradient = new SweepGradient(cx, cy,
                new int[]{Color.TRANSPARENT, changeAlpha(Color.WHITE, 40), changeAlpha(Color.WHITE, 140)
                }, new float[]{0.0f, 0.5f, 0.8f});

        Paint mSweepPaint = new Paint();
        mSweepPaint.setAntiAlias(true);
        mSweepPaint.setShader(sweepGradient);
        //先旋转画布，再绘制扫描的颜色渲染，实现扫描时的旋转效果。
        canvas.rotate(mRoteDegree, cx, cy);
        canvas.drawCircle(cx, cy, radius, mSweepPaint);
    }


    public void setMatrix(int degree) {
        mRoteDegree = degree;
        invalidate();
    }

    //线程叠加
    public Runnable runnable=new Runnable() {
        @Override
        public void run() {
            mRoteDegree+=1;
            setMatrix(mRoteDegree);
            postDelayed(runnable,20);

        }
    };
    /**
     * 改变颜色的透明度
     */
    private static int changeAlpha(int color, int alpha) {
        int red = Color.red(color);
        int green = Color.green(color);
        int blue = Color.blue(color);
        return Color.argb(alpha, red, green, blue);
    }

}

3、使用

public class ViewFragment_07 extends Fragment {
    private static final String TAG = "ViewFragment_07";
    private View_07 sweepView;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.view_07, container, false);
        sweepView = view.findViewById(R.id.view_sweep);
        new Thread(sweepView.runnable).start(); //开启线程
        return view;
    }
}