iOS view move down automatically after keyboard disappear - ios

Question

I had a iPad project, inside one of its view controllers, there are two TextFields inside a panel view (Views are build in Storyboard). What I would like to achieve is when any of those textfield become first responder (i.e. Keyboard Appears), the panel view will move up and if keyboard disappear it will move down to origin position.
Once I test move up, I found the view will automatically move back to origin position after keyboard disappear, but I didn't write any code to do that.
Code to move up:
- (void)moveUpTextFields {
if ([self.emailTextField isFirstResponder] || [self.passwordTextField isFirstResponder]) {
CGRect frame = self.textFieldPanel.frame;
frame.origin.y -= 50;
self.textFieldPanel.frame = frame;
}
}
So I would like to figure out how does that happen, and how should I achieve my goal (i.e. Move up if keyboard appear and back to original position)?
UPDATE:
To achieve my goals, it should use Keyboard Notification. Register these notifications in viewWillAppear
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWillShow:)
name:UIKeyboardWillShowNotification
object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWillHide:)
name:UIKeyboardWillHideNotification
object:nil];
}
I did this in another project long time ago, just didn't remember it at the first place :(

Answer 1

You have to listen to the keyboard events in the Notification Center, and lucky you, this is a functionality almost every app needs, so check this :)
https://github.com/aceontech/KBKeyboardHandler
It does exactly what you need but I prefer if you would understand how it behaves (registering for system notifications).
It's also available through cocoapods if you want
pod 'KBKeyboardHandler'

Answer 2

OK, so the weird behaviour is because when Keyboard Appear or Disappear, it will relayout view controller's sub views and trigger -(void)viewDidLayoutSubviews and reposition view back to StoryBoard's position. If the view is created by code then this won't be a issue.
In addition to add notifications for KeyBoard, we also need to reposition the view in viewDidLayoutSubviews since the notification triggered before layout subviews.
- (void)keyboardWillShow:(NSNotification *)notification {
CGSize keyboardSize = [notification.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue].size;
CGFloat y = self.view.frame.size.height - keyboardSize.height - self.textFieldPanel.frame.size.height - 5;
CGRect frame = self.textFieldPanel.frame;
panelViewYOffset = frame.origin.y - y;
frame.origin.y -= panelViewYOffset;
// Since it will layout subviews in viewDidLayout, why we set frame here?
// I tried to move this line, turns out the panel will move up but the animation is gone
// So this line will have a nice liner animation curve but I don't why, may be someone can explain it.
self.textFieldPanel.frame = frame;
}
- (void)keyboardWillHide:(NSNotification *)notification {
CGRect frame = self.textFieldPanel.frame;
frame.origin.y += panelViewYOffset;
self.textFieldPanel.frame = frame;
panelViewYOffset = 0;
}
In viewDidLayoutSubviews:
- (void)viewDidLayoutSubviews {
CGRect frame = self.textFieldPanel.frame;
frame.origin.y -= panelViewYOffset;
self.textFieldPanel.frame = frame;
}
Like I mentioned, this approach only works for view from StoryBoard (Interface Builder), if self.textFieldPanel is created by code, then the code in viewDidLayoutSubviews should be removed.