objective c - Logic For Moving Text Field Above Keyboard On Tap

Question

Right now, I have basic code for moving the textfield above the keyboard when you start editing. However, the size of the textfield varies based on device and orientation. So, I wrote a crude way of doing it, which doesn't stay consistently right above the keyboard, but instead will go up further when you rotate it, and so it doesn't look as professional as I would like.

The basic sense of my question is if there is a logic for getting the size of the keyboard based on device and orientation and using that value automatically and hopefully faster than this.

If that is the best way, please let me know. Otherwise, please provide input. Here is the code that I have. (This is just the move-up code, not the move down code, in order to prevent taking up too much space)

- (void)textFieldDidBeginEditing:(UITextField *)textField { 

    //Get Device Type
    NSString *deviceType = [[UIDevice currentDevice] model];

    //Animate Text Field
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDelegate:self];
    [UIView setAnimationDuration:0.4];
    [UIView setAnimationBeginsFromCurrentState:YES];

    if ([deviceType isEqualToString:@"iPhone"]) {

        //Size For iPhone
        googleBar.frame = CGRectMake(googleBar.frame.origin.x - 62.0, (googleBar.frame.origin.y - 210.0), googleBar.frame.size.width + 120.0, googleBar.frame.size.height);

    } else if ([deviceType isEqualToString:@"iPad"]) {

        //Size for iPad
        googleBar.frame = CGRectMake(googleBar.frame.origin.x - 62.0, (googleBar.frame.origin.y - 320.0), googleBar.frame.size.width + 120.0, googleBar.frame.size.height);

    } else if ([deviceType isEqualToString:@"iPod touch"]) {

        //Size For iPod Touch
        googleBar.frame = CGRectMake(googleBar.frame.origin.x - 62.0, (googleBar.frame.origin.y - 210.0), googleBar.frame.size.width + 120.0, googleBar.frame.size.height);

    } 

    [UIView commitAnimations];

} 

Answer 1

What you really want to do is observe the UIKeyboard(Did|Will)(Show|Hide) notifications. They contain in their userInfo dictionaries the beginning and ending frame, as well as the correct animation curve and durations.

So after observing this notification, when it's posted move your text field based on the size of the frame passed in the notification, according to the animation hints provided.

You can see more information in the UIWindow class reference's "notifications" section: https://developer.apple.com/library/ios/#documentation/uikit/reference/UIWindow_Class/UIWindowClassReference/UIWindowClassReference.html

Below is a sample view controller implementation. The nib for this view controller was just a single text field, with an outlet connected to it, and the text field's delegate set to the view controller.

@interface ViewController ()

- (void)viewControllerInit;

@end

@implementation ViewController

@synthesize textField;

- (id)initWithCoder:(NSCoder *)coder {
    self = [super initWithCoder:coder];
    if (self) {
        [self viewControllerInit];
    }
    return self;
}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])
    {
        [self viewControllerInit];
    }
    return self;
}


- (void)viewControllerInit
{
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
}


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


#pragma mark - Notification Handlers

- (void)keyboardWillShow:(NSNotification *)notification
{
    // I'll try to make my text field 20 pixels above the top of the keyboard
    // To do this first we need to find out where the keyboard will be.

    NSValue *keyboardEndFrameValue = [[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey];
    CGRect keyboardEndFrame = [keyboardEndFrameValue CGRectValue];

    // When we move the textField up, we want to match the animation duration and curve that
    // the keyboard displays. So we get those values out now

    NSNumber *animationDurationNumber = [[notification userInfo] objectForKey:UIKeyboardAnimationDurationUserInfoKey];
    NSTimeInterval animationDuration = [animationDurationNumber doubleValue];

    NSNumber *animationCurveNumber = [[notification userInfo] objectForKey:UIKeyboardAnimationCurveUserInfoKey];
    UIViewAnimationCurve animationCurve = [animationCurveNumber intValue];

    // UIView's block-based animation methods anticipate not a UIVieAnimationCurve but a UIViewAnimationOptions.
    // We shift it according to the docs to get this curve.

    UIViewAnimationOptions animationOptions = animationCurve << 16;


    // Now we set up our animation block.
    [UIView animateWithDuration:animationDuration 
                          delay:0.0 
                        options:animationOptions 
                     animations:^{
                         // Now we just animate the text field up an amount according to the keyboard's height,
                         // as we mentioned above.
                        CGRect textFieldFrame = self.textField.frame;
                        textFieldFrame.origin.y = keyboardEndFrame.origin.y - textFieldFrame.size.height - 40; //I don't think the keyboard takes into account the status bar
                        self.textField.frame = textFieldFrame;
                     } 
                     completion:^(BOOL finished) {}];

}


- (void)keyboardWillHide:(NSNotification *)notification
{

    NSNumber *animationDurationNumber = [[notification userInfo] objectForKey:UIKeyboardAnimationDurationUserInfoKey];
    NSTimeInterval animationDuration = [animationDurationNumber doubleValue];

    NSNumber *animationCurveNumber = [[notification userInfo] objectForKey:UIKeyboardAnimationCurveUserInfoKey];
    UIViewAnimationCurve animationCurve = [animationCurveNumber intValue];
    UIViewAnimationOptions animationOptions = animationCurve << 16;

    [UIView animateWithDuration:animationDuration 
                          delay:0.0 
                        options:animationOptions 
                     animations:^{
                         self.textField.frame = CGRectMake(20, 409, 280, 31); //just some hard coded value
                     } 
                     completion:^(BOOL finished) {}];

}
#pragma mark - View lifecycle

- (void)viewDidUnload
{
    [self setTextField:nil];
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

#pragma mark - UITextFieldDelegate

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    [self.textField resignFirstResponder];
    return YES;
}

@end