图表的集合视图展示："no chart data available" for Charts cocoapods

Question

我正在编写一个 GraphViewController class，其中包含一组图表（LineChartView 类型）。但是，当我尝试以集合视图的单元格格式显示这些图形时（使用调用的 class GraphCell），LineChartView 对象似乎没有加载任何数据，尽管这些函数是在 GraphViewController class 内部调用的。到目前为止，这是我的代码的相关部分：

class GraphViewController: UIViewController {
    
    //lazy var only calculated when called
    lazy var lineChartView: LineChartView = {
        let chartView = LineChartView()
        chartView.backgroundColor = .systemBlue
        chartView.rightAxis.enabled = false //right axis contributes nothing
        
        let yAxis = chartView.leftAxis
        yAxis.labelFont = .boldSystemFont(ofSize: 12)
        yAxis.setLabelCount(6, force: false)
        yAxis.labelTextColor = .white
        yAxis.axisLineColor = .white
        yAxis.labelPosition = .outsideChart
        
        let xAxis = chartView.xAxis
        xAxis.labelPosition = .bottom
        xAxis.labelFont = .boldSystemFont(ofSize: 12)
        xAxis.setLabelCount(6, force: false)
        xAxis.labelTextColor = .white
        xAxis.axisLineColor = .systemBlue
        
        chartView.animate(xAxisDuration: 1)
        
        return chartView
    }()
    
    var graphColl: UICollectionView!
    var graphs: [LineChartView] = []
    var graphReuseID = "graph"
    
    var homeViewController: ViewController = ViewController()
    
    let dataPts = 50
    var yValues: [ChartDataEntry] = []
    var allWordsNoPins: [Word] = []
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = .white
        
        setUpViews();
        setUpConstraints()
        
    }
    
    func setUpViews(){
        let layout = UICollectionViewFlowLayout()
        layout.minimumLineSpacing = padding/3.2
        layout.scrollDirection = .vertical
        
        graphColl = UICollectionView(frame: .zero, collectionViewLayout: layout)
        graphColl.translatesAutoresizingMaskIntoConstraints = false
        graphColl.dataSource = self
        graphColl.delegate = self
        
        //must register GraphCell class before calling dequeueReusableCell
        graphColl.register(GraphCell.self, forCellWithReuseIdentifier: graphReuseID)
        
        graphColl.backgroundColor = .white

        view.addSubview(graphColl)
        
        print("stuff assigned")
        assignData()
        setData()
        
        graphs.append(lineChartView)
        
        
    }

可以假设 setUpConstraints() 工作正常，因为图表集合确实显示了。以下是必须处理我正在使用的集合视图的所有函数：

//INSIDE GraphViewController
extension GraphViewController: UICollectionViewDelegateFlowLayout{
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize{
        
        //collectionView.frame.height -
        
        let size = 25*padding
        let sizeWidth = collectionView.frame.width - padding/3
        return CGSize(width: sizeWidth, height: size)
    }
    
}

extension GraphViewController: UICollectionViewDataSource{
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        
        return graphs.count //total number of entries
    }
    
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let graphColl = collectionView.dequeueReusableCell(withReuseIdentifier: graphReuseID, for: indexPath) as! GraphCell
        
        graphColl.configure(graph: graphs[indexPath.item])
        return graphColl
    }
}

和：

//configure function INSIDE GraphCell
    func configure(graph: LineChartView){
        chartView = graph
    }

这里是 assignData() 和 setData() 函数：

func setData(){
        let set1 = LineChartDataSet(entries: yValues, label: "Word Frequency")
        let data = LineChartData(dataSet: set1)
        
        set1.drawCirclesEnabled = true
        set1.circleRadius = 3
        set1.mode = .cubicBezier //smoothes out curve
        set1.setColor(.white)
        set1.lineWidth = 3
        set1.drawHorizontalHighlightIndicatorEnabled = false //ugly yellow line
        
        data.setDrawValues(false)
        
        
        lineChartView.data = data
    }
    
    func assignData(){
        setUpTempWords()
        
        let dataValues = allWordsNoPins
        print(allWordsNoPins.count)
        
        for i in 0...dataPts-1{
            yValues.append(ChartDataEntry(x: Double(i), y: Double(dataValues[i].count)))
        }
        
    }

也可以假设 setUpTempWords() 功能正常工作，因为下面的屏幕截图：

在这里，我直接在 GraphViewController class 内的 GraphColl UICollectionView 变量之上绘制了 LineChartView 类型的 lineChartView 对象。显示数据。但是，当我尝试在我的 GraphCell class 中绘制相同的图形时，我得到

“没有可用的图表数据。”我已经跟踪了我的 GraphViewController class 中的调用，并且根据 viewDidLoad() 函数的设置方式，我可以得出结论，正在调用 lineChartView 设置方法（assignData() 等）。作为参考，这是我的 GraphCell class 代码：

import UIKit
import Charts

class GraphCell: UICollectionViewCell {
    
    var chartView = LineChartView()
    var graphCellBox: UIView!
    
    override init(frame: CGRect){
        super.init(frame: frame)
        
        contentView.backgroundColor = .blue
        
        chartView.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(chartView)
        
        graphCellBox = UIView()
        graphCellBox.translatesAutoresizingMaskIntoConstraints = false
        //graphCellBox.backgroundColor = cellorange
        graphCellBox.layer.cornerRadius = 15.0
        contentView.addSubview(graphCellBox)
        
        setUpConstraints()
    }
    
    func setUpConstraints(){
        NSLayoutConstraint.activate([
            graphCellBox.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 5),
            graphCellBox.bottomAnchor.constraint(equalTo: contentView.bottomAnchor),
            graphCellBox.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
            graphCellBox.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),
            
            chartView.topAnchor.constraint(equalTo: graphCellBox.topAnchor),
            chartView.bottomAnchor.constraint(equalTo: graphCellBox.bottomAnchor),
            chartView.leadingAnchor.constraint(equalTo: graphCellBox.leadingAnchor),
            chartView.trailingAnchor.constraint(equalTo: graphCellBox.trailingAnchor),
        ])
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    
    func configure(graph: LineChartView){
        chartView = graph
    }
}

附带说明一下，将 lineChartView 更改为非惰性（正常）变量并不能解决此问题。我怀疑延迟声明是问题所在，因为只有调用时图才会初始化，但事实并非如此。感谢您阅读本文 post，如有任何指导或指导，我将不胜感激！

Answer 1

如果没有可重现的示例，很难对此进行测试，但是...

分配 chartView = graph 看起来有问题。

尝试使用您的 graphCellBoxgraphCellBox 作为 LineChartView 的“容器”，您使用 configure(...):

class GraphCell: UICollectionViewCell {
    
    var graphCellBox: UIView!
    
    override init(frame: CGRect){
        super.init(frame: frame)
        
        contentView.backgroundColor = .blue
        
        graphCellBox = UIView()
        graphCellBox.translatesAutoresizingMaskIntoConstraints = false
        //graphCellBox.backgroundColor = cellorange
        graphCellBox.layer.cornerRadius = 15.0
        contentView.addSubview(graphCellBox)
        
        setUpConstraints()
    }
    
    func setUpConstraints(){
        NSLayoutConstraint.activate([
            graphCellBox.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 5),
            graphCellBox.bottomAnchor.constraint(equalTo: contentView.bottomAnchor),
            graphCellBox.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
            graphCellBox.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),
        ])
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    
    func configure(graph: LineChartView){
        graph.translatesAutoresizingMaskIntoConstraints = false
        graphCellBox.addSubview(graph)

        NSLayoutConstraint.activate([
            graph.topAnchor.constraint(equalTo: graphCellBox.topAnchor),
            graph.bottomAnchor.constraint(equalTo: graphCellBox.bottomAnchor),
            graph.leadingAnchor.constraint(equalTo: graphCellBox.leadingAnchor),
            graph.trailingAnchor.constraint(equalTo: graphCellBox.trailingAnchor),
        ])
    }
}

图表的集合视图展示："no chart data available" for Charts cocoapods

collection view presentation of graph: "no chart data available" for Charts cocoapods

charts

ios

cocoapods

uicollectionview

swift