CustomTransitionDemo

今日头条小视频动画过渡效果实现

效果图

原理

自动定义 present 和 dismiss 动画,设置 viewController 的 transitioningDelegate 为自定义类对象(ImageOpeningTransitioningDelegate),自己实现过渡动画即可,本文主要讲解present自定义过渡实现

1.设置 transitioningDelegate 为 self.customTransitioningDelegate,该对象遵循 UIViewControllerTransitioningDelegate 协议,

---

...
VideoDetailsViewController *detailsViewController = [[VideoDetailsViewController alloc] init];
detailsViewController.transitioningDelegate = self.customTransitioningDelegate;
...
[self presentViewController:detailsViewController animated:YES completion:nil];

2.在 present 控制器时,会调用其animationControllerForPresentedController:presentingController: 方法,该方法需要返回一个遵守 UIViewControllerAnimatedTransitioning 协议的对象,这里我们单独抽象出一个类(ImageOpeningPresenter),

---

-(id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source
{
return [ImageOpeningPresenter new];
}

UIViewControllerAnimatedTransitioning 协议需要实现的方法

---

@protocol UIViewControllerAnimatedTransitioning <NSObject>

// 过渡动画需要的事件
- (NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext;
// 过渡上下文, transitionContext 包含参与过渡的对象,比如目标控制器和源控制器,拿到这两个控制器我们就可以写交互动画了
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext;

@optional

3.重写 animateTransition: 方法

通过 transitionContext 获取源控制器和目标控制器

---

ViewController *sourceViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
VideoDetailsViewController *targetViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];

获取 containerView ,这个视图是最底层的 view,相当于整个过渡动画的舞台,所有对象的动画过程都在它上面呈现

---

UIView *containerView = [transitionContext containerView];

过渡动画代码

---

/// 完整动画代码在 ImageOpeningPresenter.m 文件 animateTransition: 方法中

NSTimeInterval animationDuration = [self transitionDuration:transitionContext];

...

[UIView animateWithDuration:animationDuration delay:0.0 options:UIViewAnimationOptionCurveEaseOut animations:^{
    ...
}
completion:^(BOOL finished) {

    ...
    // 转场结束,这个代码很关键,一定要调用
    [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
    
}];

其他

仓库地址

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