如何自定义组件原型菜单

  onMeasure(children: Array<LayoutChild>, constraint: ConstraintSizeOptions) { 
    //获取布局最大尺寸 
    let maxWidth = px2vp(constraint.maxWidth as number); 
    let maxHeight = px2vp(constraint.maxHeight as number); 
    //获取半径 
    this.mRadius = Math.min(maxWidth,maxHeight); 
    //设置子布局大小 
    this.childSize = this.mRadius * this.DEFAULT_CHILD_DIMENSION-20; 
    this.mPadding = this.mRadius * this.PADDING_LAYOUT 
    children.forEach((child) => { 
      //对子布局进行测量 
      child.measure({ minHeight:this.childSize, minWidth: this.childSize, maxWidth: this.childSize, maxHeight: this.childSize  }) 
    }) 
  }

onLayout(children: Array<LayoutChild>, constraint: ConstraintSizeOptions) { 
    //获取子布局个数 
    const childCount = children.length; 
    //根据menu item计算item的布局占用的角度 
    const angleDelay = 360 / childCount; 
    children.forEach((child) => { 
      this.mStartAngle %= 360; 
      //计算，中心点到menu item中心的距离 
      let distanceFromCenter = this.mRadius / 2  - this.childSize / 2 - this.mPadding; 
      console.info('CustomLayout onLayout === '+ this.mStartAngle) 
      let left = this.mRadius /2 + Math.round(distanceFromCenter *Math.cos(this.mStartAngle * Math.PI / 180) - this.childSize / 2) 
      let top = this.mRadius /2 + Math.round(distanceFromCenter * Math.sin(this.mStartAngle * Math.PI / 180) - this.childSize / 2) 
      child.layout({ position: { x:left, y: top }, constraint: constraint }) 
      this.mStartAngle += angleDelay; 
    }) 
  }