             // 根据chunk的y值，计算value
             let value = calcValueByY()
             print("value:\(value)")
+            
+            setNeedsDisplay()
         }
     }
     

    
    override func draw(_ rect: CGRect) {
        let unselected = UIBezierPath()
        unselected.move(to: CGPoint(x: rect.width/2, y: 0))
        unselected.addLine(to: CGPoint(x: rect.width/2, y: rect.height))
        unselected.close()
        
        unselectColor.set()

        unselected.fill()
        
        let selected = UIBezierPath()
        selected.move(to: CGPoint(x: chunk.center.x, y: 0))
        let selected_point = CGPoint(x: chunk.center.x, y: chunk.center.y)
        selected.addLine(to: selected_point)
        selected.close()
        
