Ios PieChartView未以编程方式显示在屏幕上

我试图以编程方式显示饼图，但我无法做到这一点. 这是密码.

// Create pie chart view
let pieChart: PieChartView = {
    let pieChart = PieChartView()
    pieChart.translatesAutoresizingMaskIntoConstraints = false
    pieChart.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    return pieChart
}()

setPieChartData(chartView: pieChart, labels: labels, values: values)
        
setupViews() // Here I am adding the piechart view as follows
view.addSubview(pieChart)

NSLayoutConstraint.activate([
    pieChart.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 180),
    pieChart.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20)])
        
pieChart.setNeedsDisplay()


func setPieChartData(chartView: PieChartView, labels: [String], values: [Double]) {
    var entries: [PieChartDataEntry] = []
    for i in 0..<labels.count {
        entries.append(PieChartDataEntry(value: values[i], label: labels[i]))
    }
    let dataSet = PieChartDataSet(entries: entries, label: "Pie Chart")
    dataSet.colors = [.orange, .red]
//    dataSet.drawValuesEnabled = true // Hide values on chart
//    
//    // Set additional properties for donut chart
//    dataSet.drawIconsEnabled = true
//    dataSet.drawValuesEnabled = true
//    dataSet.sliceSpace = 2.0 // Adjust space between slices to create donut effect
            
    let data = PieChartData(dataSet: dataSet)
    chartView.data = data
}

我错过了什么？

我试着添加背景色并改变了约束条件，但它不起作用.