自定义分段控件还是..？

Question

Twitter的屏幕截图

我想要在Swift 4中使用这种分段控制。我已经研究了Apple Documents，但是找不到一些我需要的东西，例如删除边框，删除cornerRadius等。如何自定义分段控制（如Twitter的）？还是有其他选项卡/段解决方案？谢谢。

Answer 1

以下是自定义UISegmentedControl使其在选择时显示底部边框的方法：

• 为分段控件创建一个容器视图，并使用“自动布局”将其固定到其超级视图。
• 将分段控件作为子视图添加到容器视图，然后使用“自动布局”将其固定到容器视图的边缘。
• 创建一个底部的下划线视图，将其作为子视图添加到容器视图，然后对其应用自动布局（请参见示例实现）。
• 然后设置一个事件侦听器：在分段控件的值更改事件上，更改底部下划线视图的原点，以便将其移到所选段的下方。
• 我还添加了一些有关如何格式化分段控件标签的字体和文本颜色的代码，请参见下面的示例。

它将是这样的：

通过编程创建容器视图和分段控件视图的示例实现：

Swift 4.2：

import UIKit

class ViewController: UIViewController {

    private enum Constants {
        static let segmentedControlHeight: CGFloat = 40
        static let underlineViewColor: UIColor = .blue
        static let underlineViewHeight: CGFloat = 2
    }

    // Container view of the segmented control
    private lazy var segmentedControlContainerView: UIView = {
        let containerView = UIView()
        containerView.backgroundColor = .clear
        containerView.translatesAutoresizingMaskIntoConstraints = false
        return containerView
    }()

    // Customised segmented control
    private lazy var segmentedControl: UISegmentedControl = {
        let segmentedControl = UISegmentedControl()

        // Remove background and divider colors
        segmentedControl.backgroundColor = .clear
        segmentedControl.tintColor = .clear

        // Append segments
        segmentedControl.insertSegment(withTitle: "First", at: 0, animated: true)
        segmentedControl.insertSegment(withTitle: "Second", at: 1, animated: true)
        segmentedControl.insertSegment(withTitle: "Third", at: 2, animated: true)

        // Select first segment by default
        segmentedControl.selectedSegmentIndex = 0

        // Change text color and the font of the NOT selected (normal) segment
        segmentedControl.setTitleTextAttributes([
            NSAttributedStringKey.foregroundColor: UIColor.black,
            NSAttributedStringKey.font: UIFont.systemFont(ofSize: 16, weight: .regular)], for: .normal)

        // Change text color and the font of the selected segment
        segmentedControl.setTitleTextAttributes([
            NSAttributedStringKey.foregroundColor: UIColor.blue,
            NSAttributedStringKey.font: UIFont.systemFont(ofSize: 16, weight: .bold)], for: .selected)

        // Set up event handler to get notified when the selected segment changes
        segmentedControl.addTarget(self, action: #selector(segmentedControlValueChanged), for: .valueChanged)

        // Return false because we will set the constraints with Auto Layout
        segmentedControl.translatesAutoresizingMaskIntoConstraints = false
        return segmentedControl
    }()

    // The underline view below the segmented control
    private lazy var bottomUnderlineView: UIView = {
        let underlineView = UIView()
        underlineView.backgroundColor = Constants.underlineViewColor
        underlineView.translatesAutoresizingMaskIntoConstraints = false
        return underlineView
    }()

    private lazy var leadingDistanceConstraint: NSLayoutConstraint = {
        return bottomUnderlineView.leftAnchor.constraint(equalTo: segmentedControl.leftAnchor)
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        // Add subviews to the view hierarchy
        // (both segmentedControl and bottomUnderlineView are subviews of the segmentedControlContainerView)
        view.addSubview(segmentedControlContainerView)
        segmentedControlContainerView.addSubview(segmentedControl)
        segmentedControlContainerView.addSubview(bottomUnderlineView)

        // Constrain the container view to the view controller
        let safeLayoutGuide = self.view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
            segmentedControlContainerView.topAnchor.constraint(equalTo: safeLayoutGuide.topAnchor),
            segmentedControlContainerView.leadingAnchor.constraint(equalTo: safeLayoutGuide.leadingAnchor),
            segmentedControlContainerView.widthAnchor.constraint(equalTo: safeLayoutGuide.widthAnchor),
            segmentedControlContainerView.heightAnchor.constraint(equalToConstant: Constants.segmentedControlHeight)
            ])

        // Constrain the segmented control to the container view
        NSLayoutConstraint.activate([
            segmentedControl.topAnchor.constraint(equalTo: segmentedControlContainerView.topAnchor),
            segmentedControl.leadingAnchor.constraint(equalTo: segmentedControlContainerView.leadingAnchor),
            segmentedControl.centerXAnchor.constraint(equalTo: segmentedControlContainerView.centerXAnchor),
            segmentedControl.centerYAnchor.constraint(equalTo: segmentedControlContainerView.centerYAnchor)
            ])

        // Constrain the underline view relative to the segmented control
        NSLayoutConstraint.activate([
            bottomUnderlineView.bottomAnchor.constraint(equalTo: segmentedControl.bottomAnchor),
            bottomUnderlineView.heightAnchor.constraint(equalToConstant: Constants.underlineViewHeight),
            leadingDistanceConstraint,
            bottomUnderlineView.widthAnchor.constraint(equalTo: segmentedControl.widthAnchor, multiplier: 1 / CGFloat(segmentedControl.numberOfSegments))
            ])
    }

    @objc private func segmentedControlValueChanged(_ sender: UISegmentedControl) {
        changeSegmentedControlLinePosition()
    }

    // Change position of the underline
    private func changeSegmentedControlLinePosition() {
        let segmentIndex = CGFloat(segmentedControl.selectedSegmentIndex)
        let segmentWidth = segmentedControl.frame.width / CGFloat(segmentedControl.numberOfSegments)
        let leadingDistance = segmentWidth * segmentIndex
        UIView.animate(withDuration: 0.3, animations: { [weak self] in
            self?.leadingDistanceConstraint.constant = leadingDistance
            self?.layoutIfNeeded()
        })
    }

}