UIButton没有为.infoLight显示带有“i”的圆圈

Question

出于某种原因，当我运行下面的函数以编程方式添加UIButton时，没有显示带有“i”的iOS按钮标准圈。（我确实希望以编程方式而不是在界面中执行此操作） builder） - 我将它添加到UIPageViewController。我在屏幕的左下方有一个按钮，我将它设置为.backgroundColor = .lightGray以验证它已被添加到子视图＆amp;工作正常（图片左侧，下方）。对我可能最基本的东西的想法？非常感谢！

func configureAboutButton() {
    let aboutButtonHeight: CGFloat = 44
    let aboutButtonWidth: CGFloat = 44
    aboutButton = UIButton(type: .infoLight)
    aboutButton.tintColor = UIColor.red
    aboutButton = UIButton(frame: CGRect(x: 0, y: view.frame.height - aboutButtonHeight, width: aboutButtonWidth, height: aboutButtonHeight))
    aboutButton.backgroundColor = .lightGray
    aboutButton.addTarget(self, action: #selector(segueToAboutVC), for: .touchUpInside)
    view.addSubview(aboutButton)
}

奇怪的是，如果我在设置背景颜色的下方添加此行，则右侧的图像显示（否则我会在左侧显示图像）。

aboutButton.setTitle（“X”，for：。normal）

Answer 1

问题

使用aboutButton = UIButton(type: .infoLight))创建按钮后，再次使用aboutButton = UIButton(frame: CGRect(x: 0, y: view.frame.height - aboutButtonHeight, width: aboutButtonWidth, height: aboutButtonHeight))创建按钮。这就是为什么信息图标没有显示。

解决方案

只需设置框架属性aboutButton.frame = CGRect(x: 0, y: view.frame.height - aboutButtonHeight, width: aboutButtonWidth, height: aboutButtonHeight)即可设置按钮的框架，然后删除aboutButton = UIButton(frame: CGRect(x: 0, y: view.frame.height - aboutButtonHeight, width: aboutButtonWidth, height: aboutButtonHeight))：

func configureAboutButton() {
  let aboutButtonHeight: CGFloat = 44
  let aboutButtonWidth: CGFloat = 44
  aboutButton = UIButton(type: .infoLight)
  aboutButton.tintColor = UIColor.red
  aboutButton.frame = CGRect(x: 0, y: view.frame.height - aboutButtonHeight, width: aboutButtonWidth, height: aboutButtonHeight)
  aboutButton.backgroundColor = .lightGray
  aboutButton.addTarget(self, action: #selector(segueToAboutVC), for: .touchUpInside)
  view.addSubview(aboutButton)
}

提示

更好的解决方案是使用auto layout options to set constraints programmatically之一。在下面的版本中，我使用布局锚点来设置约束。例如，您可以找到here自动布局的优点。

func configureAboutButton() {
  aboutButton = UIButton(type: .infoLight)
  // need to set to false, to set the constraints programmatically
  aboutButton.translatesAutoresizingMaskIntoConstraints = false
  aboutButton.tintColor = UIColor.red
  aboutButton.backgroundColor = .lightGray
  aboutButton.addTarget(self, action: #selector(segueToAboutVC), for: .touchUpInside)
  view.addSubview(aboutButton)

  // set the constraints via Layout Anchors
  // x, y, w, h
  aboutButton.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
  aboutButton.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
  aboutButton.widthAnchor.constraint(equalToConstant: 44).isActive = true
  aboutButton.heightAnchor.constraint(equalToConstant: 44).isActive = true
}