我在调整表格视图大小和滚动到活动文本字段时遇到困难，当键盘出现时，当视图以模态方式呈现在 iPad 上的表单时。它在 iPhone 上运行良好，因为我不必考虑表单视图的偏移量 - 我可以将 tableview 的底部 contentInset 更改为与键盘高度相同。但是，这在 iPad 上不起作用，因为表单以及它的 tableview 不会占据整个屏幕。
计算tableview的新底部contentInset应该是多少的最佳方法是什么？
【问题讨论】：
标签： ios objective-c uitableview
好的，我自己偶然发现了这个问题。我创建了一个适用于各种情况的解决方案（因此不仅适用于以表单形式呈现的视图控制器）。解决方案在 Swift 3 中，因此您仍然需要将其转换为 Objective-C，但如果您仔细阅读 cmets，这应该不是问题。
解决方案的关键是在键盘动画完成时更新tableView（或scrollview）插图，并且表单在它的新位置上。
在你的 UIViewController 子类中添加：
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillChangeFrame(_:)), name: .UIKeyboardWillChangeFrame, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillChangeFrame(_:)), name: .UIKeyboardWillHide, object: nil)
}
这将添加一个观察者，以防键盘显示/隐藏。我们还需要取消订阅这些通知，否则应用会崩溃：
deinit {
NotificationCenter.default.removeObserver(self)
}
最后，最重要的代码：
func getTableViewInsets(keyboardHeight: CGFloat) -> UIEdgeInsets {
// Calculate the offset of our tableView in the
// coordinate space of of our window
let window = (UIApplication.shared.delegate as! AppDelegate).window!
let tableViewFrame = tableView.superview!.convert(tableView.frame, to: window)
// BottomInset = part of keyboard that is covering the tableView
let bottomInset = keyboardHeight
- ( window.frame.height - tableViewFrame.height - tableViewFrame.origin.y )
// Return the new insets + update this if you have custom insets
return UIEdgeInsetsMake(
tableView.contentInset.top,
tableView.contentInset.left,
bottomInset,
tableView.contentInset.right
)
}
func keyboardWillChangeFrame(_ notification: Notification){
guard let info = (notification as NSNotification).userInfo else {
return
}
guard let animationDuration = info[UIKeyboardAnimationDurationUserInfoKey] as? TimeInterval else {
return
}
// Default: keyboard will hide:
var keyboardHeight: CGFloat = 0
if notification.name == .UIKeyboardWillChangeFrame {
// The keyboard will show
guard let keyboardFrame = info[UIKeyboardFrameEndUserInfoKey] as? NSValue else {
return
}
keyboardHeight = keyboardFrame.cgRectValue.height
}
let contentInsets = getTableViewInsets(keyboardHeight: keyboardHeight)
UIView.animate(withDuration: animationDuration, animations: {
self.tableView.contentInset = contentInsets
self.tableView.scrollIndicatorInsets = contentInsets
}, completion: {(completed: Bool) -> Void in
// Chances are the position of our view has changed, (form sheet)
// so we need to double check our insets
let contentInsets = self.getTableViewInsets(keyboardHeight: keyboardHeight)
self.tableView.contentInset = contentInsets
self.tableView.scrollIndicatorInsets = contentInsets
})
}
【讨论】：
let bottomInset = keyboardHeight - (window.frame.maxY - tableViewFrame.maxY)的bottomInset计算
UIKeyboardWillChangeFrame而不是UIKeyboardWillShow？
首先，感谢 Simon Backx，我在实际项目中使用了他的方法。它有效，但有一些场景没有被充分考虑。我优化了他的回答。我原本想在他的答案下方添加评论，但我们没有足够的声誉来添加 cmets。我只能创建一个新的答案，希望这个答案可以帮助别人。
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillChangeFrame(_:)), name: UIResponder.keyboardWillChangeFrameNotification, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillHide(_:)), name: UIResponder.keyboardWillHideNotification, object: nil)
}
deinit {
NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillChangeFrameNotification, object: nil)
NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillHideNotification, object: nil)
}
contentInsets
private func calculateTableViewContentInsets(keyboardHeight: CGFloat) -> UIEdgeInsets {
let window = (UIApplication.shared.delegate as! AppDelegate).window!
let tableViewFrame = tableView.superview!.convert(tableView.frame, to: window)
let bottomInset = keyboardHeight
- (window.frame.height - tableViewFrame.height - tableViewFrame.origin.y)
- tableView.safeAreaInsets.bottom
var newInsets = tableView.contentInset
newInsets.bottom = bottomInset
return newInsets
}
@objc private func keyboardWillChangeFrame(_ sender: Notification) {
guard let userInfo = sender.userInfo else { return }
guard let keyboardFrame = userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect else { return }
guard let duration = userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double else { return }
let keyboardHeight = keyboardFrame.height
let contentInsets = calculateTableViewContentInsets(keyboardHeight: keyboardHeight)
UIView.animate(withDuration: duration, animations: {
self.tableView.contentInset = contentInsets
self.tableView.scrollIndicatorInsets = contentInsets
}, completion: { _ in
let contentInsets = self.calculateTableViewContentInsets(keyboardHeight: keyboardHeight)
self.tableView.contentInset = contentInsets
self.tableView.scrollIndicatorInsets = contentInsets
})
}
@objc private func keyboardWillHide(_ sender: Notification) {
guard let userInfo = sender.userInfo else { return }
guard let duration = userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double else { return }
UIView.animate(withDuration: duration) {
self.tableView.contentInset.bottom = 0
self.tableView.scrollIndicatorInsets.bottom = 0
}
}
【讨论】：
为什么不调整整个 UITableView 的大小而不是设置 contentInset ？
我会在显示键盘时修改 tableview 的约束。
在您的 .h 中创建一个实际约束的引用，当键盘隐藏或不隐藏时该约束将发生变化。 （例如，tableview 底部和 superview 底部之间的边距。）
@property (weak, nonatomic) IBOutlet NSLayoutConstraint *bottomMargin;
为UIKeyboardWillShowNotification添加观察者
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
和实际的方法
-(void)keyboardWillShow:(NSNotification*)notification {
[self.view layoutIfNeeded];
NSDictionary* userInfo = [notification userInfo];
CGRect keyboardFrameEnd;
[[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardFrameEnd]; //getting the frame of the keyboard
//you can get keyboard animation's duration and curve with UIKeyboardAnimationCurveUserInfoKey and UIKeyboardAnimationDurationUserInfoKey if you want to animate it
//calculate the new values of the constraints of your UITableView
//for the example, the new value will be the keyboard height
self.bottomMargin.constant = keyboardFrameEnd.size.height;
[self.view layoutIfNeeded];
}
【讨论】：
我在这个帖子中发布了一个演示如何做到这一点的链接：
iOS 7 iPad Orientation issue, when view moves upside after keyboard appears on UITextField
它还包括一个keyboardWillShow 函数，但它对 iOS 8 友好：
-(void)onKeyboardWillShow:(NSNotification*)notification
{
// The user has turned on the onscreen keyboard.
//
NSDictionary *info = [notification userInfo];
NSValue *kbFrame = [info objectForKey:UIKeyboardFrameEndUserInfoKey];
CGRect keyboardFrame = [kbFrame CGRectValue];
keyboardFrame = [self.view convertRect:keyboardFrame fromView:nil];
CGFloat keyboardHeight = keyboardFrame.size.height;
}
我发现在 iOS 8.x 中，如果我没有使用convertRect 函数，iPad 有时会在横向模式下报告 1024 像素的键盘高度。
【讨论】：