提高 CAShapeLayer 绘制的折线图的性能

问题描述

我通过 CAShapeLayer 中的 MTKView 创建了一个折线图。在某些情况下，此折线图每秒更新一次，但在当前的实现中，每当图表更新（每秒）时，都会有一个微小的冻结时刻，因为它会再次绘制所有内容。我尝试了所有我能想到的方法来提高它的性能，但我无法修复它。当新数据到来时，这个冻结时刻不允许图表平滑移动。

这是我的代码的一部分：

class LineChartView: MTKView,uiscrollviewdelegate {

  private let scrollView: UIScrollView = UIScrollView()

  public var lineGap: CGFloat = 0.7

  var dataEntries: [PointEntry]? {
       didSet {
          dispatchQueue.main.async {
             self.setNeedsLayout()
          }
       }
    }
        
    private var hrDataPoints: [CGPoint]?
        
    override func layoutSubviews() {
       if let dataEntries = dataEntries {

          scrollView.frame = CGRect(x: 50,y: 0,width: frame.size.width,height: frame.size.height)
          scrollView.contentSize = CGSize(width: 50 + CGFloat(dataEntries.count) * lineGap,height: frame.size.height)
          mainLayer.frame = CGRect(x: 0,width: CGFloat(dataEntries.count) * lineGap,height: frame.size.height)

          dataLayer.frame = CGRect(x: 0,y: topSpace,width: mainLayer.frame.width,height: mainLayer.frame.height - topSpace - bottomSpace)
          hrDataPoints = convertDataEntriesToPoints(entries: dataEntries)
          clean()
          drawCharts()
       }
    }
}

// MARK: - Drawing

extension LineChartView {
    
  private func convertDataEntriesToPoints(entries: [PointEntry]) -> [CGPoint] {

     if let max = entries.max()?.value,let min = entries.min()?.value {

        let filteredMax = max + emptySpaceAboveAndBelowChart
        let filteredMin = min - emptySpaceAboveAndBelowChart

        var result: [CGPoint] = []
        let minMaxrange: CGFloat = CGFloat(filteredMax - filteredMin) * topHorizontalLine

        for i in 0 ..< entries.count {

           let height = dataLayer.frame.height * (1 - ((CGFloat(entries[i].value) - CGFloat(filteredMin)) / minMaxrange))
           let point = CGPoint(x: CGFloat(i) * lineGap + 40,y: height)
           result.append(point)
        }
        return result
     }
     return []
  }
    
  private func drawCharts() {
     let lineLayer = CAShapeLayer()
     lineLayer.linewidth = 2
     lineLayer.fillColor = UIColor.clear.cgColor

     guard let path = createPath() else { return }
     lineLayer.path = path.cgPath
     lineLayer.strokeColor = UIColor.green.cgColor
     lineLayer.drawsAsynchronously = true
     dataLayer.addSublayer(lineLayer)
  }
    
  private func createPath() -> UIBezierPath? {

      var dataPoints: [CGPoint] = []

      guard let points = hrDataPoints,points.count > 0 else { return nil }
      dataPoints = points

      let path = UIBezierPath()
      path.move(to: dataPoints[0])

      for i in 1 ..< dataPoints.count {
         path.addLine(to: dataPoints[i])
      }
      return path
   }
}

// MARK: - Cleaning

extension LineChartView {

  private func clean() {
       mainLayer.sublayers?.forEach({
          if $0 is CATextLayer {
             $0.removeFromSuperlayer()
          }
       })

       gridLayer.sublayers?.forEach({ $0.removeFromSuperlayer() })
       dataLayer.sublayers?.forEach({ $0.removeFromSuperlayer() })
    }
}

并且在新数据到来的每一秒内，新数据都会附加到 dataEntries 中。如果有人能给我一些建议，我将不胜感激。

谢谢

解决方法

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