iOS自定义转场（custom transition)

    iOS中，从一个也没切换到另一个页面的效果叫转场（transition）。UINavgationController、UIViewController默认的转场效果有时不能满足项目的要求，需要我们创造新的效果，这就需要用到自定义转场啦！

    


    自定义的步骤：

    1、准备两个UIViewController，通常是从presentdingViewController（简写presenting）跳转到 presentedViewController（简写presented）；

    2、presenteing中需要实现<UIViewControllerTransitioningDelegate>接口，然后重写该接口中的方法animationControllerForPresentedController、animationControllerForDismissedController。如果presentingVC中调用了[self presentViewController:
 ]，则会执行接口中的方法，这个方法就会返回自定义转场的效果；

    3、第二步中animationControllerForPresentedController方法应该返回转场动画的对象，它实现了<UIViewControllerAnimatedTransitioning>接口。该接口只有两个方法，transitionDuration和animateTransition，通过animateTransition就能让页面切换时，随心所欲的动起来。

    步骤2的代码：

#pragma mark UIViewControllerTransitioningDelegate
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source{

return [BPTransitionAnimator new];
//    return [[BPPresentaionController alloc] initWithPresentedViewController:presented presentingViewController:presenting];
}

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed {

return [BPTransitionAnimator new];
}

    步骤3的代码：

//
//  BPTransitionAnimator.m
//  Demo
//
//  Created by bingcai on 16/4/18.
//  Copyright © 2016年 Linda. All rights reserved.
//

#import "BPTransitionAnimator.h"

@implementation BPTransitionAnimator

- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext{

return 1.0;
}

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext{

UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController *toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];

UIView *containerView = [transitionContext containerView];

UIView *fromView = [transitionContext viewForKey:UITransitionContextFromViewKey];
UIView *toView = [transitionContext viewForKey:UITransitionContextToViewKey];

fromView.frame = [transitionContext initialFrameForViewController:fromViewController];
toView.frame = [transitionContext finalFrameForViewController:toViewController];

fromView.alpha = 1.0;
toView.alpha = 0.0;

[containerView addSubview:toView];

NSTimeInterval transitionDuration = [self transitionDuration:transitionContext];

[UIView animateWithDuration:transitionDuration animations:^{

fromView.alpha = 0.0;
toView.alpha = 1.0;

} completion:^(BOOL finished){

BOOL isCancelled = [transitionContext transitionWasCancelled];
[transitionContext completeTransition:!isCancelled];
}];
}

@end

Demo下载

    

上述的方法都是支持iOS7的，但在使用的时候可能会用到iOS8的方法，需要注意。