Creating a Page-Curl Animation for UIWebView Pages
In recent years, the use of web views has become increasingly popular in mobile app development. Web views allow developers to embed web content into their apps, making it easy to integrate online resources, share content, and provide users with an alternative way of consuming information. However, one common challenge that developers face when working with UIWebViews is animating the transition between pages.
In this article, we’ll explore how to create a seamless page-curl animation for UIWebView pages. We’ll break down the process into manageable steps, discussing the technical details and providing example code to help you get started.
Understanding Web View Animations
Before diving into the specifics of creating a page-curl animation, let’s take a moment to review how web view animations work. In iOS 4 and later, Apple introduced the concept of “web view transitions” which allow developers to smoothly transition between different pages within a web view. There are three built-in transition types: pageCurl, pageSwipe, and coverVertical.
The Role of UIPageViewController
To create a page-curl animation for UIWebView pages, we’ll need to use the UIPageViewController class. This class is designed specifically for managing the transitions between web view pages. By using UIPageViewController, you can take advantage of its built-in transition capabilities and customize your animations as needed.
Setting Up the Page Controller
To get started with creating a page-curl animation, we’ll need to set up our UIPageViewController instance. Here’s an example of how you might initialize it:
#import <UIKit/UIKit.h>
@interface ViewController : UIViewController
@property (nonatomic, strong) UIPageViewController *pageViewController;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Create a new instance of the page controller
self.pageViewController = [[UIPageViewController alloc] initWithViewControllers:@[self.webView] options:UIPageViewControllerOptions pageOrientation:UIPageOrientationPortrait orientations:[NSIndexSet indexSetWithIndex:0]];
// Set up the page view controller's delegate
self.pageViewController.delegate = self;
// Add the page view controller to our main view hierarchy
[self.view addSubview:self.pageViewController.view];
}
In this example, we’ve created a new instance of UIPageViewController and initialized it with an array of view controllers. We’ve also set up the delegate property and added the page view controller’s view to our main view hierarchy.
Configuring the Page Curl Animation
Now that we have our page controller set up, let’s take a closer look at how we can configure the page-curl animation. By default, UIPageViewController uses a simple swipe transition between pages. However, we want to create a more sophisticated page-curl animation.
To achieve this, we’ll need to subclass UIPageViewController and override its viewControllerTransitionToView method. Here’s an example of how you might implement this:
#import <UIKit/UIKit.h>
@interface CustomPageViewController : UIPageViewController
@end
@implementation CustomPageViewController
- (void)viewControllerTransitionToView:(UIViewController *)viewController withTransitionStyle:(UIPageTransitionStyle)style duration:(NSTimeInterval)duration options:(id<UIPageViewControllerTransitionOptions>)options afterCompletion:(void (^)(void))completion {
[super viewControllerTransitionToView:viewController withTransitionStyle:style duration:duration options:nil afterCompletion:^(void){
// Animate the transition
UIView *pageView = self.viewControllers[0].view;
.pageView.transform = CGAffineTransformScale(pageView.transform, 1.5, 1.5);
}];
}
In this example, we’ve overridden the viewControllerTransitionToView method and added our own animation code inside the completion block.
Adding the Animation Code
The next step is to add the actual animation code to the view controller’s transition method. Here’s an updated version of the code that includes a basic page-curl animation:
#import <UIKit/UIKit.h>
@interface CustomPageViewController : UIPageViewController
@end
@implementation CustomPageViewController
- (void)viewControllerTransitionToView:(UIViewController *)viewController withTransitionStyle:(UIPageTransitionStyle)style duration:(NSTimeInterval)duration options:(id<UIPageViewControllerTransitionOptions>)options afterCompletion:(void (^)(void))completion {
[super viewControllerTransitionToView:viewController withTransitionStyle:style duration:duration options:nil afterCompletion:^(void){
// Save the current page's size and position
CGRect pageFrame = self.viewControllers[0].view.frame;
CGFloat currentPageWidth = pageFrame.size.width;
CGFloat currentPageHeight = pageFrame.size.height;
// Create a new animation context
UAAnimationContext *animationContext = [UAAnimationContext animationContextWithPageViewController:self];
// Calculate the target size and position for the next page
CGRect nextPageFrame = self.viewControllers[1].view.frame;
CGFloat nextPageWidth = nextPageFrame.size.width;
CGFloat nextPageHeight = nextPageFrame.size.height;
// Animate the transition by scaling the current page
UIView *pageView = self.viewControllers[0].view;
[UIView animateWithDuration:duration delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
pageView.transform = CGAffineTransformScale(pageView.transform, 1.5, 1.5);
} completion:^(BOOL finished){
// Remove the animation scale when the transition is complete
pageView.transform = CGAffineTransformIdentity;
}];
// Animate the next page by scaling it to fit the screen
UIView *nextPageView = self.viewControllers[1].view;
[UIView animateWithDuration:duration delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
nextPageView.transform = CGAffineTransformScale(nextPageView.transform, 1.5, 1.5);
} completion:^(BOOL finished){
// Remove the animation scale when the transition is complete
nextPageView.transform = CGAffineTransformIdentity;
}];
// Restore the saved page size and position
pageView.frame = CGRectZero;
self.viewControllers[0].view.frame = pageFrame;
nextPageView.frame = CGRectZero;
self.viewControllers[1].view.frame = nextPageFrame;
}];
}
@end
In this example, we’ve added code to save the current page’s size and position before scaling the next page. We’ve also added animation code to scale both pages simultaneously.
Putting it All Together
Now that we have our custom page controller set up with a page-curl animation, let’s take a look at how we can put everything together in a complete example.
Here’s an updated version of the code that includes the entire project:
#import <UIKit/UIKit.h>
@interface ViewController : UIViewController
@property (nonatomic, strong) CustomPageViewController *pageViewController;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Create a new instance of the page controller
self.pageViewController = [[CustomPageViewController alloc] initWithViewControllers:@[self.webView] options:UIPageViewControllerOptions pageOrientation:UIPageOrientationPortrait orientations:[NSIndexSet indexSetWithIndex:0]];
// Set up the page view controller's delegate
self.pageViewController.delegate = self;
// Add the page view controller to our main view hierarchy
[self.view addSubview:self.pageViewController.view];
}
- (UIWebView *)webView {
// Create a new instance of UIWebView
UIWebView *webView = [[UIWebView alloc] init];
webView.frame = self.view.bounds;
return webView;
}
@end
@implementation CustomPageViewController
- (instancetype)initWithViewControllers:(NSArray<UIViewController *> *)viewControllers options:(UIPageViewControllerOptions)options pageOrientation:(UIPageOrientation)pageOrientation orientations:(NSIndexSet *)orientations {
self = [super initWithTransitioningDelegate:self];
if (self) {
// Create a new animation context
UAAnimationContext *animationContext = [UAAnimationContext animationContextWithPageViewController:self];
// Configure the page view controller
self.viewControllers = viewControllers;
self.options = options;
self.pageOrientation = pageOrientation;
self.orientationMask = orientations;
// Set up the transition animation
self.transitionStyle = UIPageTransitionStylePageUnCurl;
self.duration = 0.5f;
}
return self;
}
- (void)viewDidLoad {
[super viewDidLoad];
}
@end
@implementation CustomPageViewController (TransitioningDelegate)
- (id<UIPageViewControllerTransitioning>)transitioning '(UIViewController *)fromVC toVC:(UIViewController *)toVC' {
UAAnimationContext *animationContext = [UAAnimationContext animationContextWithPageViewController:self];
// Save the current page's size and position
CGRect currentPageFrame = self.viewControllers[0].view.frame;
CGFloat currentPageWidth = currentPageFrame.size.width;
CGFloat currentPageHeight = currentPageFrame.size.height;
// Create a new animation context for the transition
UAAnimationContext *transitionAnimationContext = [UAAnimationContext animationContextWithPageViewController:self];
// Calculate the target size and position for the next page
CGRect nextPageFrame = self.viewControllers[1].view.frame;
CGFloat nextPageWidth = nextPageFrame.size.width;
CGFloat nextPageHeight = nextPageFrame.size.height;
return ^(id<UIPageViewControllerTransitioning> transitioning) {
// Animate the transition by scaling the current page
UIView *currentPageView = self.viewControllers[0].view;
[UIView animateWithDuration:0.5f delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
currentPageView.transform = CGAffineTransformScale(currentPageView.transform, 1.5, 1.5);
} completion:^(BOOL finished){
// Remove the animation scale when the transition is complete
currentPageView.transform = CGAffineTransformIdentity;
}];
// Animate the next page by scaling it to fit the screen
UIView *nextPageView = self.viewControllers[1].view;
[UIView animateWithDuration:0.5f delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
nextPageView.transform = CGAffineTransformScale(nextPageView.transform, 1.5, 1.5);
} completion:^(BOOL finished){
// Remove the animation scale when the transition is complete
nextPageView.transform = CGAffineTransformIdentity;
}];
// Restore the saved page size and position
currentPageView.frame = CGRectZero;
self.viewControllers[0].view.frame = currentPageFrame;
nextPageView.frame = CGRectZero;
self.viewControllers[1].view.frame = nextPageFrame;
};
}
@end
@implementation UAAnimationContext
+ (UAAnimationContext *)animationContextWithPageViewController:(CustomPageViewController *)pageViewController {
return [[self alloc] initWithPageViewController:pageViewController];
}
- (instancetype)initWithPageViewController:(CustomPageViewController *)pageViewController {
self = [super init];
if (self) {
_pageViewController = pageViewController;
}
return self;
}
@end
In this example, we’ve added code to save the current page’s size and position before scaling the next page. We’ve also added animation code to scale both pages simultaneously.
Conclusion
In this tutorial, we’ve learned how to create a custom page controller with a page-curl animation using UIKit. We’ve covered topics such as:
- Creating a custom page controller subclass
- Subclassing
UIPageViewControllerand overriding its methods - Using
UAAnimationContextto manage the transition animation - Implementing a basic page-curl animation using
UIView animateWithDuration
By following this tutorial, you should now have a better understanding of how to create custom transitions in your iOS apps.
Last modified on 2024-02-21