我正在构建一个 Messenger 应用。
我目前的键盘通知功能如下:
func handleKeyboardNotification(notification: NSNotification) {
if let userInfo = notification.userInfo {
let keyboardFrame = userInfo[UIKeyboardFrameEndUserInfoKey]?.CGRectValue()
print(keyboardFrame)
let isKeyboardShowing = notification.name == UIKeyboardWillShowNotification
bottomConstraint?.constant = isKeyboardShowing ? -keyboardFrame!.height : 0
UIView.animateWithDuration(0, delay: 0, options: UIViewAnimationOptions.CurveEaseOut, animations: {
self.view.layoutIfNeeded()
}, completion: { (completed) in
if isKeyboardShowing {
let indexPath = NSIndexPath(forItem: self.messages!.count - 1, inSection: 0)
self.collectionView?.scrollToItemAtIndexPath(indexPath, atScrollPosition: .Bottom, animated: true)
}
})
}
}
(bottomConstraint.constant 是指位于屏幕底部或键盘框架顶部的消息输入文本字段)
但是，我希望完成参数中的操作与键盘打开同时发生，而不是在键盘打开之后发生。目前，当我关闭键盘时，它似乎可以自动布局，但当我打开它时却不行。
到目前为止，我尝试了很多方法都无济于事。 有什么建议吗？
最佳答案
如果您希望在完成中编写的代码块与键盘按下同时发生，那么您不应该将其写入完成 block 中。 您可以在调用带持续时间的动画函数之前使用 dispatch_async，这样它就可以同时工作:
func handleKeyboardNotification(notification: NSNotification) {
if let userInfo = notification.userInfo {
let keyboardFrame = userInfo[UIKeyboardFrameEndUserInfoKey]?.CGRectValue()
print(keyboardFrame)
let isKeyboardShowing = notification.name == UIKeyboardWillShowNotification
bottomConstraint?.constant = isKeyboardShowing ? -keyboardFrame!.height : 0
DispatchQueue.main.async {
if isKeyboardShowing {
let indexPath = NSIndexPath(forItem: self.messages!.count - 1, inSection: 0)
self.collectionView?.scrollToItemAtIndexPath(indexPath, atScrollPosition: .Bottom, animated: true)
}
UIView.animateWithDuration(0, delay: 0, options: UIViewAnimationOptions.CurveEaseOut, animations: {self.view.layoutIfNeeded()}, completion: nil})
}
}
关于ios - 滚动 UICollectionView 以响应键盘通知，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42711382/