Swift - UIView 在更改选项卡控制器选项卡时移动答案

【问题标题】：Swift - UIView moves when changing tab controller tabsSwift - UIView 在更改选项卡控制器选项卡时移动
【发布时间】：2021-10-06 08:06:28
【问题描述】：

在viewDidAppear 里面我有一个包含这段代码的函数，为了制作一个UIView：

let contentView = UIView()
    func addSleepingView() {
        
        contentView.backgroundColor = .systemYellow.withAlphaComponent(0.25)
        
        view.addSubview(contentView)
        
        contentView.translatesAutoresizingMaskIntoConstraints = false
        contentView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        contentView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
        
        // Anchor your view right above the tabBar
        contentView.bottomAnchor.constraint(equalTo: (tabBarController?.tabBar.topAnchor)!).isActive = true
        contentView.heightAnchor.constraint(equalToConstant: 50).isActive = true
        
        let label = UILabel()
        label.text = "Test"
        label.frame = CGRect(x: 0, y: 0, width: 25, height: 34.0)
        label.lineBreakMode = .byWordWrapping
        label.numberOfLines = 0
        label.textAlignment = .center
        label.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(label)
        label.centerXAnchor.constraint(equalTo: contentView.centerXAnchor).isActive = true
        label.centerYAnchor.constraint(equalTo: contentView.centerYAnchor).isActive = true
        
        let button = UIButton()
        button.setImage(UIImage(systemName: "arrow.clockwise", withConfiguration: UIImage.SymbolConfiguration(scale: .large)), for: UIControl.State.normal)
        button.tintColor = .systemGray
        button.frame = CGRect(x: self.view.bounds.width-42, y: 8, width: 34, height: 34.0)
        button.isUserInteractionEnabled = true
        button.addTarget(self, action: #selector(wakeupFunction), for: .touchUpInside)
        contentView.addSubview(button)
        let button2 = UIButton()
        button2.setImage(UIImage(systemName: "exclamationmark.triangle", withConfiguration: UIImage.SymbolConfiguration(scale: .large)), for: UIControl.State.normal)
        button2.tintColor = .label
        button2.frame = CGRect(x: 8, y: 8, width: 34, height: 34.0)
        button2.isUserInteractionEnabled = false
        contentView.addSubview(button2)
        
        contentView.bringSubviewToFront(button)
    }

这就是它的样子：

现在这正是我想要的。当我更改标签时，问题就来了。例如，转到最后一个选项卡，然后再次返回第一个选项卡。然后它看起来像这样：

我在这里做错了什么？

【问题讨论】：

标签： ios swift uiview uitabbarcontroller

【解决方案1】：

您可以在 DispatchQueue.main 块中添加激活约束的代码

您可以更改更新的线路，它将开始按您的预期工作。

// 将视图锚定在 tabBar 的正上方

DispatchQueue.main.async 
{

        self.contentView.bottomAnchor.constraint(equalTo: (self.tabBarController?.tabBar.topAnchor)!).isActive = true
        self.contentView.heightAnchor.constraint(equalToConstant: 50).isActive = true
    }

【讨论】：