iOS键盘弹出/收起时屏幕偏移异常问题求助

我来帮你搞定这个键盘偏移的问题！你遇到的多次操作后屏幕逐渐偏移、键盘弹出后底部出现空白的问题，主要是当前代码里的两个关键问题导致的，咱们一步步来修复：

问题根源 #

• 错误的键盘Frame获取键：你用了UIKeyboardFrameBeginUserInfoKey，这个值是键盘开始显示时的初始位置，而键盘显示是有动画过渡的，这个初始位置的高度并不等于最终显示在屏幕上的键盘高度，多次触发后就会导致偏移累加。
• 偏移逻辑的判断漏洞：直接通过self.view.frame.origin.y == 0来判断是否需要偏移，一旦键盘高度发生变化（比如切换到表情键盘），这个判断就会失效，导致复位时的偏移量错误，最终屏幕越来越偏。

修复方案 #

方案1：修正现有代码逻辑 #

我们需要改用UIKeyboardFrameEndUserInfoKey获取键盘最终的显示高度，同时和键盘动画同步，并且确保复位时准确回到初始位置：

override func viewDidLoad() {
    super.viewDidLoad()
    // 注册键盘通知（兼容iOS各版本写法）
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide), name: UIResponder.keyboardWillHideNotification, object: nil)
}

@objc func keyboardWillShow(notification: NSNotification) {
    // 获取键盘最终的显示frame
    guard let keyboardFrame = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue else { return }
    let keyboardHeight = keyboardFrame.cgRectValue.height
    
    // 仅当视图在初始位置时执行偏移，避免重复操作
    if self.view.frame.origin.y == 0 {
        // 同步键盘动画的时长与曲线，保证视觉流畅
        let duration = notification.userInfo?[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double ?? 0.25
        let curve = notification.userInfo?[UIResponder.keyboardAnimationCurveUserInfoKey] as? UInt ?? UIView.AnimationOptions.curveEaseInOut.rawValue
        
        UIView.animate(withDuration: duration, delay: 0, options: UIView.AnimationOptions(rawValue: curve)) {
            self.view.frame.origin.y -= keyboardHeight
        }
    }
}

@objc func keyboardWillHide(notification: NSNotification) {
    // 直接复位到初始位置，不依赖键盘高度，彻底避免累加错误
    if self.view.frame.origin.y != 0 {
        let duration = notification.userInfo?[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double ?? 0.25
        let curve = notification.userInfo?[UIResponder.keyboardAnimationCurveUserInfoKey] as? UInt ?? UIView.AnimationOptions.curveEaseInOut.rawValue
        
        UIView.animate(withDuration: duration, delay: 0, options: UIView.AnimationOptions(rawValue: curve)) {
            self.view.frame.origin.y = 0
        }
    }
}

方案2：更优的AutoLayout方式（推荐） #

如果你的界面是用AutoLayout构建的，直接修改view的frame容易和约束冲突，更推荐通过调整底部约束的constant值来实现：

1. 给主视图底部添加一个约束，关联为IBOutlet：

@IBOutlet weak var bottomConstraint: NSLayoutConstraint!

2. 修改通知处理代码：

@objc func keyboardWillShow(notification: NSNotification) {
    guard let keyboardFrame = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue else { return }
    let keyboardHeight = keyboardFrame.cgRectValue.height
    let duration = notification.userInfo?[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double ?? 0.25
    let curve = notification.userInfo?[UIResponder.keyboardAnimationCurveUserInfoKey] as? UInt ?? UIView.AnimationOptions.curveEaseInOut.rawValue
    
    bottomConstraint.constant = keyboardHeight
    UIView.animate(withDuration: duration, delay: 0, options: UIView.AnimationOptions(rawValue: curve)) {
        self.view.layoutIfNeeded()
    }
}

@objc func keyboardWillHide(notification: NSNotification) {
    let duration = notification.userInfo?[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double ?? 0.25
    let curve = notification.userInfo?[UIResponder.keyboardAnimationCurveUserInfoKey] as? UInt ?? UIView.AnimationOptions.curveEaseInOut.rawValue
    
    bottomConstraint.constant = 0
    UIView.animate(withDuration: duration, delay: 0, options: UIView.AnimationOptions(rawValue: curve)) {
        self.view.layoutIfNeeded()
    }
}

方案3：如果使用UIScrollView（或子类如UITableView） #

如果你的界面包含滚动视图，苹果官方推荐的方式是调整contentInset和scrollIndicatorInsets，这样滚动视图会自动适配键盘，同时避免偏移问题：

@objc func keyboardWillShow(notification: NSNotification) {
    guard let keyboardFrame = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue else { return }
    let keyboardHeight = keyboardFrame.cgRectValue.height
    
    // 调整滚动视图的内边距，适配键盘高度
    scrollView.contentInset.bottom = keyboardHeight
    scrollView.scrollIndicatorInsets.bottom = keyboardHeight
}

@objc func keyboardWillHide(notification: NSNotification) {
    // 复位内边距
    scrollView.contentInset.bottom = 0
    scrollView.scrollIndicatorInsets.bottom = 0
}

额外注意事项 #

• 记得在deinit里移除通知观察者，避免内存泄漏：

deinit {
    NotificationCenter.default.removeObserver(self)
}

• iOS 13及以上，推荐使用NotificationCenter的block注册方式，不需要手动移除观察者（系统会自动处理）：

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(forName: UIResponder.keyboardWillShowNotification, object: nil, queue: .main) { [weak self] notification in
        // 处理键盘显示逻辑
    }
    // 同理注册键盘隐藏的通知
}

内容的提问来源于stack exchange，提问作者user