图表的集合视图演示：图表 cocoapods 的“没有可用的图表数据”

Posted 2023-03-14

【中文标题】图表的集合视图演示：图表 cocoapods 的“没有可用的图表数据”

【英文标题】：collection view presentation of graph: "no chart data available" for Charts cocoapods

【发布时间】：2021-03-31 15:16:54

【问题描述】：

我正在编写一个 GraphViewController 类，其中包含一组图形（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表时（使用被调用的类GraphCell），LineChartView 对象似乎没有加载任何数据，即使这些函数在内部调用GraphViewController 班级。到目前为止，这是我的代码的相关位：

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，因为图形集合确实出现了。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() 函数工作正常，因为下面的截图：

在这里，我在 GraphViewController 类中的 GraphColl UICollectionView 变量上直接绘制了 LineChartView 类型的 lineChartView 对象。显示数据。但是，当我尝试在 GraphCell 类中绘制相同的图表时，我得到了

“没有可用的图表数据。”我已经在我的 GraphViewController 类中跟踪了调用，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 类代码：

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，将 lineChartView 更改为非惰性（普通）变量并不能解决此问题。我怀疑惰性声明是问题所在，因为该图仅在调用时才会被初始化，但事实并非如此。感谢您阅读这篇文章，我将不胜感激任何方向或指导！

【问题讨论】：

在UICollectionViewCell 中，您正在使用chartView 配置（添加子视图、锚点等）所有内容，但之后，您将其替换为chartView = graph，期望之前的视图仍然正确？我不认为它应该是这样工作的。相反，正如问题中所建议的那样，对图表使用“容器视图”，即“占位符视图”。

【参考方案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 作为您通过configure(...) 传递的LineChartView 的“容器”：

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),
        ])