UITextField: move view when keyboard appears

Question

I'm currently working on an iPhone application with a single view, which has multiple UITextFields for input. When the keyboard shows, it overlays the bottom textfields. So I added the corresponding textFieldDidBeginEditing: method, to move the view up, which works great:

- (void)textFieldDidBeginEditing:(UITextField *)textField {
    if ( ( textField != inputAmount ) && ( textField != inputAge ) ) {
        NSTimeInterval animationDuration = 0.300000011920929;
        CGRect frame = self.view.frame;
        frame.origin.y -= kOFFSET_FOR_KEYBOARD;
        frame.size.height += kOFFSET_FOR_KEYBOARD;
        [UIView beginAnimations:@"ResizeForKeyboard" context:nil];
        [UIView setAnimationDuration:animationDuration];
        self.view.frame = frame;
        [UIView commitAnimations];      
    }
}

This method checks, if the source of the message is one of the textfields that are visible when the keyboard shows, and if not, it moves the view up.

I also added the textFieldDidEndEnditing: method, which moves the view down again (and updates some model objects according to the changed input):

- (void)textFieldDidEndEditing:(UITextField *)textField {
    if ( ( textField != inputMenge ) && ( textField != inputAlter ) ) {
        NSTimeInterval animationDuration = 0.300000011920929;
        CGRect frame = self.view.frame;
        frame.origin.y += kOFFSET_FOR_KEYBOARD;
        frame.size.height -= kOFFSET_FOR_KEYBOARD;
        [UIView beginAnimations:@"ResizeForKeyboard" context:nil];
        [UIView setAnimationDuration:animationDuration];
        self.view.frame = frame;
        [UIView commitAnimations];      
    }
    // Additional Code
}

However, this solution has a simple flaw: When I finish editing one of the "hidden" textfields and touch another textfield, the keyboard vanishes, the view moves down, the view moves up again and the keyboard reappears.

Is there any possibility to keep the keyboard from vanishing and reappearing between two edits (of the "hidden" textfields - so that the view only moves when the selected textfield changes from one that would be hidden by the keyboard to one that would not be hidden)?

Answer 1

This solution is based on ComSubVie's one.

Advantages:

• It supports device rotation - works for all orientations;
• It doesn't hardcode the values for animation duration and curve, it reads them from the keyboard notification;
• It utilizes UIKeyboardWillShowNotification instead of UIKeyboardDidShowNotification to sync keyboard animation and custom actions;
• It doesn't use the deprecated UIKeyboardBoundsUserInfoKey;
• It handles keyboard resize due to pressing the International key;
• Fixed memory leak by unregistering for keyboard events;
• All keyboard handling code is encapsulated in a separate class - KBKeyboardHandler;
• Flexibility - KBKeyboardHandler class may be easy extended / modified to better suit specific needs;

Limitations:

• Works for iOS 4 and above, it needs small modifications to support older versions;
• It works for applications with a single UIWindow. If you use multiple UIWindows, you may need to modify retrieveFrameFromNotification: method.

Usage:

Include KBKeyboardHandler.h, KBKeyboardHandler.m and KBKeyboardHandlerDelegate.h in your project. Implement the KBKeyboardHandlerDelegate protocol in your view controller - it consists of a single method, which will be called when keyboard is shown, hidden or its size is changed. Instantiate the KBKeyboardHandler and set its delegate (typically self). See sample MyViewController below.

KBKeyboardHandler.h:

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@protocol KBKeyboardHandlerDelegate;

@interface KBKeyboardHandler : NSObject

- (id)init;

// Put 'weak' instead of 'assign' if you use ARC
@property(nonatomic, assign) id<KBKeyboardHandlerDelegate> delegate; 
@property(nonatomic) CGRect frame;

@end

KBKeyboardHandler.m:

#import "KBKeyboardHandler.h"
#import "KBKeyboardHandlerDelegate.h"

@implementation KBKeyboardHandler

- (id)init
{
    self = [super init];
    if (self)
    {
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(keyboardWillShow:)
                                                     name:UIKeyboardWillShowNotification
                                                   object:nil];

        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(keyboardWillHide:)
                                                     name:UIKeyboardWillHideNotification
                                                   object:nil];
    }

    return self;
}

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    [super dealloc];
}

@synthesize delegate;
@synthesize frame;

- (void)keyboardWillShow:(NSNotification *)notification
{
    CGRect oldFrame = self.frame;    
    [self retrieveFrameFromNotification:notification];

    if (oldFrame.size.height != self.frame.size.height)
    {
        CGSize delta = CGSizeMake(self.frame.size.width - oldFrame.size.width,
                                  self.frame.size.height - oldFrame.size.height);
        if (self.delegate)
            [self notifySizeChanged:delta notification:notification];
    }
}

- (void)keyboardWillHide:(NSNotification *)notification
{
    if (self.frame.size.height > 0.0)
    {
        [self retrieveFrameFromNotification:notification];
        CGSize delta = CGSizeMake(-self.frame.size.width, -self.frame.size.height);

        if (self.delegate)
            [self notifySizeChanged:delta notification:notification];
    }

    self.frame = CGRectZero;
}

- (void)retrieveFrameFromNotification:(NSNotification *)notification
{
    CGRect keyboardRect;
    [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardRect];
    self.frame = [[UIApplication sharedApplication].keyWindow.rootViewController.view convertRect:keyboardRect fromView:nil];
}

- (void)notifySizeChanged:(CGSize)delta notification:(NSNotification *)notification
{
    NSDictionary *info = [notification userInfo];

    UIViewAnimationOptions curve;
    [[info objectForKey:UIKeyboardAnimationCurveUserInfoKey] getValue:&curve];

    NSTimeInterval duration;
    [[info objectForKey:UIKeyboardAnimationDurationUserInfoKey] getValue:&duration];

    void (^action)(void) = ^{
        [self.delegate keyboardSizeChanged:delta];
    };

    [UIView animateWithDuration:duration
                          delay:0.0
                        options:curve
                     animations:action
                     completion:nil];    
}

@end

KBKeyboardHandlerDelegate.h:

@protocol KBKeyboardHandlerDelegate

- (void)keyboardSizeChanged:(CGSize)delta;

@end

Sample MyViewController.h:

@interface MyViewController : UIViewController<KBKeyboardHandlerDelegate>
...
@end

Sample MyViewController.m:

@implementation MyViewController
{
    KBKeyboardHandler *keyboard;
}

- (void)dealloc
{
    keyboard.delegate = nil;
    [keyboard release];
    [super dealloc];
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    keyboard = [[KBKeyboardHandler alloc] init];
    keyboard.delegate = self;
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    keyboard.delegate = nil;
    [keyboard release];
    keyboard = nil;
}

- (void)keyboardSizeChanged:(CGSize)delta
{
    // Resize / reposition your views here. All actions performed here 
    // will appear animated.
    // delta is the difference between the previous size of the keyboard 
    // and the new one.
    // For instance when the keyboard is shown, 
    // delta may has width=768, height=264,
    // when the keyboard is hidden: width=-768, height=-264.
    // Use keyboard.frame.size to get the real keyboard size.

    // Sample:
    CGRect frame = self.view.frame;
    frame.size.height -= delta.height;
    self.view.frame = frame;
}

UPDATE: Fixed iOS 7 warning, thanks @weienv.