问题
I have a scrollView that i want to scroll up when the keyboard is shown.
I have a crash with this error when the keyboard show :
2014-09-29 14:48:50.738 swrd[1563:472888] -[swrd.EditPhotoViewController keyboardWasShown]: unrecognized selector sent to instance 0x14ed36640
Here is my code, what's wrong ?:
func registerForKeyboardNotifications ()-> Void {
NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWasShown", name: UIKeyboardDidShowNotification, object: nil)
NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWillBeHidden", name: UIKeyboardWillHideNotification, object: nil)
}
func deregisterFromKeyboardNotifications () -> Void {
let center: NSNotificationCenter = NSNotificationCenter.defaultCenter()
center.removeObserver(self, name: UIKeyboardDidHideNotification, object: nil)
center.removeObserver(self, name: UIKeyboardWillHideNotification, object: nil)
}
func keyboardWasShown (notification: NSNotification) {
let info : NSDictionary = notification.userInfo!
let keyboardSize = info.objectForKey(UIKeyboardFrameBeginUserInfoKey)?.frame
let insets: UIEdgeInsets = UIEdgeInsetsMake(self.scrollView.contentInset.top, 0, keyboardSize!.height, 0)
self.scrollView.contentInset = insets
self.scrollView.scrollIndicatorInsets = insets
self.scrollView.contentOffset = CGPointMake(self.scrollView.contentOffset.x, self.scrollView.contentOffset.y + keyboardSize!.height)
}
func keyboardWillBeHidden (notification: NSNotification) {
let info : NSDictionary = notification.userInfo!
let keyboardSize = info.objectForKey(UIKeyboardFrameBeginUserInfoKey)?.frame
let insets: UIEdgeInsets = UIEdgeInsetsMake(self.scrollView.contentInset.top, 0, keyboardSize!.height, 0)
self.scrollView.contentInset = insets
self.scrollView.scrollIndicatorInsets = insets
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(true)
self.registerForKeyboardNotifications()
}
override func viewWillDisappear(animated: Bool) {
super.viewWillDisappear(true)
self.deregisterFromKeyboardNotifications()
}
回答1:
In your code, keyboardWasShown and keyboardWasHidden each take an argument, the NSNotification. You need to terminate your selectors in addObserver with a colon so that it gets passed. I.e., keyboardWasShown and keyboardWasShown: are different selectors.
NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWasShown:", name: UIKeyboardDidShowNotification, object: nil)
回答2:
See a self-contained solution below:
private func startObservingKeyboardEvents() {
NSNotificationCenter.defaultCenter().addObserver(self,
selector:Selector("keyboardWillShow:"),
name:UIKeyboardWillShowNotification,
object:nil)
NSNotificationCenter.defaultCenter().addObserver(self,
selector:Selector("keyboardWillHide:"),
name:UIKeyboardWillHideNotification,
object:nil)
}
private func stopObservingKeyboardEvents() {
NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillShowNotification, object: nil)
NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillHideNotification, object: nil)
}
func keyboardWillShow(notification: NSNotification) {
if let userInfo = notification.userInfo {
if let keyboardSize: CGSize = userInfo[UIKeyboardFrameEndUserInfoKey]?.CGRectValue().size {
let contentInset = UIEdgeInsetsMake(0.0, 0.0, keyboardSize.height, 0.0);
}
}
}
func keyboardWillHide(notification: NSNotification) {
let contentInset = UIEdgeInsetsZero;
}
Use the contentInset variable to adjust the content insets.
回答3:
In my case, was need some changes in the codes above:
1 - First you need put a Scrollview in your view, and set constraints like this:
It's important your scrollView be grater than view.
2 - Put your TextField's and other components you need.
3 - Link ScrollView to the ViewController with @IBOutlet
4 - Add the Delegate to ScrollView:
class ViewController: UIViewController, UITextFieldDelegate, UIScrollViewDelegate {
...
5 - Add the Observer's:
override func viewWillAppear(animated: Bool) {
self.startKeyboardObserver()
}
override func viewWillDisappear(animated: Bool) {
self.stopKeyboardObserver()
}
private func startKeyboardObserver(){
NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWillShow:", name: UIKeyboardWillShowNotification, object: nil) //WillShow and not Did ;) The View will run animated and smooth
NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWillHide:", name: UIKeyboardWillHideNotification, object: nil)
}
private func stopKeyboardObserver() {
NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillShowNotification, object: nil)
NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillHideNotification, object: nil)
}
6 - Add The code to scroll, calculating KeyboardSize.
func keyboardWillShow(notification: NSNotification) {
if let userInfo = notification.userInfo {
if let keyboardSize: CGSize = userInfo[UIKeyboardFrameEndUserInfoKey]?.CGRectValue().size {
let contentInset = UIEdgeInsetsMake(0.0, 0.0, keyboardSize.height, 0.0);
self.scrollView.contentInset = contentInset
self.scrollView.scrollIndicatorInsets = contentInset
self.scrollView.contentOffset = CGPointMake(self.scrollView.contentOffset.x, 0 + keyboardSize.height) //set zero instead self.scrollView.contentOffset.y
}
}
}
func keyboardWillHide(notification: NSNotification) {
if let userInfo = notification.userInfo {
if let keyboardSize: CGSize = userInfo[UIKeyboardFrameEndUserInfoKey]?.CGRectValue().size {
let contentInset = UIEdgeInsetsZero;
self.scrollView.contentInset = contentInset
self.scrollView.scrollIndicatorInsets = contentInset
self.scrollView.contentOffset = CGPointMake(self.scrollView.contentOffset.x, self.scrollView.contentOffset.y)
}
}
}
来源：https://stackoverflow.com/questions/26100545/swift-scroll-the-view-up-when-keyboard-shows