public class MySearch extends View {
  Paint paint;
  Path searchPath; //搜索的圆
  Path ciclePath; //外圆
  //获得宽高
  int w;
  int h;
  //这是保存截取时，返回的坐标点
  float serpos[];
  float cicpos[];
  //测量 path 的类
  PathMeasure measure;
  //动画产生的实时数据
  float value;
  public MySearch(Context context) {
    this(context,null);
  }
  public MySearch(Context context, @Nullable AttributeSet attrs) {
    this(context,attrs,0);
  }
  public MySearch(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    //获得屏幕的宽高
    WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
    w = wm.getDefaultDisplay().getWidth();
    h = wm.getDefaultDisplay().getHeight();
    //初始化数据
    serpos = new float[2];
    cicpos = new float[2];
    //画笔
    paint = new Paint();
    paint.setStyle(Paint.Style.STROKE);
    paint.setDither(true);
    paint.setStrokeWidth(6);
    paint.setAntiAlias(true);
    //初始化路径
    initPath();
    //初始化动画
    initAnimator();
  }
  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    //移动画布的远点到屏幕中心
    canvas.translate(w/2,h/5);
    paint.setColor(Color.BLUE);
    //这是截取方法返回的路径
    Path dra = new Path();
    //解除硬件加速，不然没效果
    dra.reset();
    dra.lineTo(0,0);
    //设置当前需要测量的path
    measure.setPath(searchPath,false);
    //开始截取
    boolean s = measure.getSegment(measure.getLength()*value,measure.getLength(),dra,true);
    //绘制路径
    canvas.drawPath(dra,paint);
  }
  /**
   * 初始化路径
   */
  public void initPath(){
    paint.setColor(Color.BLUE);
    //搜索的圆
    searchPath = new Path();
    RectF rectF = new RectF(-50,-50,50,50);
    searchPath.addArc(rectF,45,359.9f);
    //辅助圆
    ciclePath = new Path();
    RectF rectF1 = new RectF(-100,-100,100,100);
    ciclePath.addArc(rectF1,45,359.9f);
    //测量类
    measure = new PathMeasure();
    measure.setPath(searchPath,false);
    //获取坐标
    measure.getPosTan(0,serpos,null);
    measure.setPath(ciclePath,false);
    //获取坐标
    measure.getPosTan(0,cicpos,null);
    //根据两点坐标绘制线
    searchPath.lineTo(cicpos[0],cicpos[1]);
  }
  /**
   * 初始化动画
   */
  public void initAnimator(){
    ValueAnimator animator = ValueAnimator.ofFloat(0,1);
    animator.setDuration(2600);
    animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
      @Override
      public void onAnimationUpdate(ValueAnimator animation) {
        value = (float) animation.getAnimatedValue();
        postInvalidate();
      }
    });
    animator.start();
  }
}