使用ios-charts设置LineChartData标签的背景颜色和空格/填充

pod 'Charts'

import Charts
import UIKit

class CustomMarkerView: MarkerView {
    private var text = ""
    private let textLabel: UILabel = {
        let label = UILabel()
        label.textColor = .white
        label.textAlignment = .center
        label.font = UIFont.systemFont(ofSize: 12)
        return label
    }()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        addSubview(textLabel)
        backgroundColor = UIColor.black.withAlphaComponent(0.7)
        layer.cornerRadius = 5
        layer.masksToBounds = true
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func refreshContent(entry: ChartDataEntry, highlight: Highlight) {
        text = "Value: \(entry.y)"
        textLabel.text = text
        textLabel.sizeToFit()
        let size = textLabel.frame.size
        self.frame = CGRect(x: 0, y: 0, width: size.width + 16, height: size.height + 8)
        textLabel.frame = CGRect(x: 8, y: 4, width: size.width, height: size.height)
    }
    
    override func offsetForDrawing(atPoint point: CGPoint) -> CGPoint {
        let size = self.bounds.size
        let offset = CGPoint(x: -size.width / 2, y: -size.height)
        return offset
    }
}

import UIKit
import Charts

class ViewController: UIViewController {
    var lineChartView: LineChartView!

    override func viewDidLoad() {
        super.viewDidLoad()
        
        lineChartView = LineChartView()
        lineChartView.frame = CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height / 2)
        self.view.addSubview(lineChartView)
        
        let entries = (0..<10).map { (i) -> ChartDataEntry in
            let val = Double(i) * Double(arc4random_uniform(10) + 3)
            return ChartDataEntry(x: Double(i), y: val)
        }
        
        let dataSet = LineChartDataSet(entries: entries, label: "Sample Data")
        dataSet.colors = [NSUIColor.blue]
        dataSet.circleColors = [NSUIColor.red]
        
        let data = LineChartData(dataSet: dataSet)
        lineChartView.data = data
        
        let marker = CustomMarkerView(frame: CGRect(x: 0, y: 0, width: 80, height: 40))
        marker.chartView = lineChartView
        lineChartView.marker = marker
    }
}