最近在项目中需要解决苹果系统输入法遮挡输入框的问题，预期结果为：
若键盘弹出后会遮挡输入框，则输入框随键盘弹起上移，输入法切换时输入框始终保持在距键盘上方 4pt 处;若键盘弹出后不会遮挡输入框，但切换输入法后会遮挡输入框，则输入框需要在切换后上移，随后输入法切换时输入框始终保持在键盘上方 4pt 处。
效果示意：
一. 背景
开发环境：iOS14.2 + Xcode v12.2 + Swift5
设备：iPhoneSE（其他机型测试有效）
页面采用自动布局
二. 实现方式
在viewWillAppear中添加键盘弹出、收起、frame变化的通知
override func viewWillAppear(_ animated: Bool) {super.viewWillAppear(animated)// 键盘弹出监听，解决键盘挡住输入框的问题NotificationCenter.default.addObserver(self,selector: #selector(keyboardWillAppear),name: UIResponder.keyboardWillShowNotification,object: nil)NotificationCenter.default.addObserver(self,selector: #selector(keyboardHasAppear),name: UIResponder.keyboardDidShowNotification,object: nil)NotificationCenter.default.addObserver(self,selector: #selector(keyboardWillDisappear),name: UIResponder.keyboardWillHideNotification,object: nil)NotificationCenter.default.addObserver(self,selector: #selector(keyboardFrameDidChange),name: UIResponder.keyboardDidChangeFrameNotification,object: nil)}
（相关链接：iOS键盘通知）
添加成员变量：
private var keyboardFlag: Int = 0 // 键盘弹起情况，收起=0private var deltaHeight: CGFloat = 0 // 键盘与输入框间距private var nameFieldBottomHeight: CGFloat = 0 // 输入框底部到页面底部距离private var transformDistance: CGFloat = 0 // 页面移动距离
实现 keyboardWillAppear：
@objcfunc keyboardWillAppear(noti: Notification) {// 获得软键盘的高let keyboardSize = (noti.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValuelet keyboardHeight = keyboardSize?.height// 计算输入框和软键盘的高度差/* nickNameEditView.containerView：输入框 */let rect = self.nickNameEditView.containerView.convert(self.nickNameEditView.containerView.bounds,to: self.view) // 将rect由rect所在视图转换到目标视图view中，返回在目标视图view中的rectself.nameFieldBottomHeight = self.view.bounds.height - (rect.origin.y + rect.size.height) // 输入框底部到页面底部距离self.deltaHeight = (keyboardHeight ?? 0) - self.nameFieldBottomHeight // 键盘高度 与 输入框底部到页面底部 距离差if self.keyboardFlag == 0, self.deltaHeight > 0 {// 键盘原来是收起的，且遮挡输入框self.pageContainerView.transform = CGAffineTransform(a: 1, b: 0, c: 0, d: 1,tx: 0, ty: -self.deltaHeight - 4)self.transformDistance = -self.deltaHeight - 4/* -4：为了使键盘距离输入框底部距离为4pt，该值可改 *//* pageContainerView：需要移动的控件，包成一个view */}}
实现keyboardHasAppear：
@objcfunc keyboardHasAppear() {self.keyboardFlag = 1 // 键盘已弹出}
实现keyboardWillDisappear：
@objcfunc keyboardWillDisappear() {if self.keyboardFlag == 0 {// 软键盘收起的时候恢复原始偏移self.pageContainerView.transform = CGAffineTransform.identityself.transformDistance = 0}}
实现 keyboardFrameDidChange，解决切换输入法动态调整：
@objcfunc keyboardFrameDidChange(noti: Notification) {// 获得软键盘的高let keyboardSize = (noti.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValuelet keyboardHeight = keyboardSize?.height// 计算输入框和软键盘的高度差self.deltaHeight = (keyboardHeight ?? 0) - (self.nameFieldBottomHeight + self.transformDistance)// 键盘在弹出的情况下如果frame有变化就改变输入框位置if self.keyboardFlag == 1 {// 如果页面之前没有上移，键盘遮挡输入框，页面上移; 页面之前有上移，输入框下降到键盘上方4pt处if (self.transformDistance == 0 && self.deltaHeight > 0) || (self.transformDistance != 0) {self.pageContainerView.transform = CGAffineTransform(a: 1, b: 0, c: 0, d: 1,tx: 0, ty: -self.deltaHeight - 4)self.transformDistance = -self.deltaHeight - 4}}}
点击空白区域收取键盘：
// 收起键盘override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {if self.nickNameEditView.nameTextField.isFirstResponder {self.keyboardFlag = 0self.nickNameEditView.nameTextField.resignFirstResponder()}}
在 viewWillDisappear 中移除通知：
override func viewWillDisappear(_ animated: Bool) {super.viewWillDisappear(animated)NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillShowNotification, object: nil)NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardDidShowNotification, object: nil)NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillHideNotification, object: nil)NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardDidChangeFrameNotification, object: nil)}
End.
由于我水平尚浅，计算和实现方法可能有很多不足，有任何问题欢迎评论交流～
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