Background Resizing on Keyboard Visibility

Introduction

When working with iOS applications, it’s common to encounter situations where the keyboard appears and disappears unexpectedly, affecting the layout of our views. In this article, we’ll explore a solution for resizing the background view when the keyboard becomes visible.

The Problem

The provided code snippet demonstrates a scenario where clicking on a text field triggers the appearance of a date picker pop-up. Upon further interactions with continuous text fields, the keyboard is displayed in an unexpected way, as illustrated by the image. This issue arises from the fact that the scroll view’s content size does not change when the keyboard appears.

Understanding Keyboard Notification

To solve this problem, we need to understand how iOS notifies us of keyboard appearances and disappearances using notifications. Specifically, we’ll utilize the UIKeyboardDidShowNotification and UIKeyboardWillHideNotification notifications.

Solution Overview

Our approach involves:

1. Adding observers for these notifications in the view controller’s viewDidLoad method.
2. Defining two methods: keyboardShown and keyboardHidden, which will be called when the keyboard appears or disappears, respectively.
3. Resizing the background view accordingly using these methods.

Implementing Keyboard Notification

First, let’s add observers for the notifications in our viewDidLoad method:

- (void)viewDidLoad {
    [super viewDidLoad];
    
    NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
    [center addObserver:self selector:@selector(keyboardShown) name:UIKeyboardDidShowNotification object:nil];
    [center addObserver:self selector:@selector(keyboardHidden) name:UIKeyboardWillHideNotification object:nil];
}

keyboardShown Method

This method will be called when the keyboard appears. We’ll resize our background view to accommodate the new keyboard size:

- (void)keyboardShown {
    [self animateBackgroundView:YES];
}

- (void)animateBackgroundView:(BOOL)animated {
    CGRect scrollFrame = self.scrollView.bounds;
    CGFloat scrollHeight = MAX(scrollFrame.size.height, self.view.bounds.size.height - KEYBOARD_ANIMATION_DURATION);
    
    // Adjust background view size
    self.backgroundView.frame = CGRectMake(0, 0, self.view.bounds.size.width, scrollHeight);
    
    [self.view addSubview:self.backgroundView];
}

In this method:

• We first retrieve the current scroll frame and calculate the maximum possible height for our view.
• Adjust the background view’s size based on the calculated height to ensure it encompasses the entire screen.
• Finally, we add the background view as a subview of the main view.

keyboardHidden Method

This method will be called when the keyboard disappears. We’ll resize our background view again, taking into account its original size:

- (void)keyboardHidden {
    [self animateBackgroundView:NO];
}

Here, we simply call the animateBackgroundView method with animated set to NO, effectively removing the background view from the main view.

Animated Background View Method

This method is responsible for animating the removal of the background view when the keyboard disappears or resizing it when the keyboard appears. We’ll use this method to adjust our background view’s size and position smoothly:

- (void)animateBackgroundView:(BOOL)animated {
    // ...
    
    if (!animated) {
        [self.view removeSubview:self.backgroundView];
    }
}

In the animation block, we first update the scroll frame and calculate the new maximum possible height. We then adjust our background view’s size based on this height.

To smoothly animate the removal of the background view when the keyboard disappears:

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationBeginsFromCurrentState:YES];
[UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];

[self.view setFrame:self.view.bounds];

[UIView commitAnimations];

Similarly, to animate the resizing of the background view when the keyboard appears:

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationBeginsFromCurrentState:YES];
[UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];

[self.view setFrame:self.view.bounds];

[UIView commitAnimations];

Conclusion

Resizing the background view when the keyboard becomes visible involves adding observers for keyboard notifications and defining methods to resize our view accordingly. By understanding how iOS notifies us of keyboard appearances and disappearances, we can create a smooth animation that adjusts our background view’s size and position in response to these events.

To demonstrate this approach:

• Create a new project in Xcode with the Single View App template.
• Add a UIScrollView and a TextField to your view hierarchy.
• Implement the code snippets provided above to resize your background view when the keyboard appears or disappears.
• Run the app on your device to see the animation effect.

By following this solution, you can create an intuitive user experience where your app’s background view adapts seamlessly to keyboard visibility.

Last modified on 2024-05-23