简介

在iOS 7之前，我们只能使用系统提供的转场效果，iOS 7之后苹果开放了相关API允许我们对转场效果进行全面定制，它是 以协议的方式开放了自定义转场的API，协议的好处是不再拘泥于具体的某个类，只要是遵守该协议的对象都能参与转场，非常灵活，这样对自定义转场动画以及交互手段的支持带来了无限可能。

动画控制器

新建一个继承NSObject的类，枚举转场类型，遵守UIViewControllerAnimatedTransitioning协议，实现协议方法，自定义转场的动画效果。

typedef NS_ENUM(NSUInteger, NSTransitionStyle) {
    NSTransitionStylePush,
    NSTransitionStylePop,
    NSTransitionStylePresent,
    NSTransitionStyleDismiss
};

@interface CustomTransition : NSObject <UIViewControllerAnimatedTransitioning>
@property (nonatomic, assign) NSTransitionStyle style;
@end

@implementation CustomTransition

#pragma mark - UIViewControllerAnimatedTransitioning
- (void)animateTransition:(nonnull id<UIViewControllerContextTransitioning>)transitionContext {
    switch (self.style) {
        case NSTransitionStylePush:
            [self pushAnimation:transitionContext];
            break;
        case NSTransitionStylePop:
            [self popAnimation:transitionContext];
            break;
        case NSTransitionStylePresent:
            [self presentAnimation:transitionContext];
            break;
        case NSTransitionStyleDismiss:
            [self dismissAnimation:transitionContext];
            break;
        default:
            break;
    }
}
- (NSTimeInterval)transitionDuration:(nullable id<UIViewControllerContextTransitioning>)transitionContext {
    return 1.0f;
}

#pragma mark - Animation
/**
 push动画
 @param transitionContext 转场上下文
 */
- (void)pushAnimation:(id<UIViewControllerContextTransitioning>)transitionContext {
    
}

/**
 pop动画实现
 @param transitionContext 转场上下文
 */
- (void)popAnimation:(id<UIViewControllerContextTransitioning>)transitionContext {
    
}


/**
 present动画实现
 @param transitionContext 转场上下文
 */
- (void)presentAnimation:(id<UIViewControllerContextTransitioning>)transitionContext {
    
}

/**
 dismiss动画实现
 @param transitionContext 转场上下文
 */
- (void)dismissAnimation:(id<UIViewControllerContextTransitioning>)transitionContext {
    
}

@end

转场环境

提供转场中需要的数据，遵守UIViewControllerContextTransitioning协议。

• 获取控制器

//获取转场相关的两个控制器 iOS7的API
UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];

• 获取视图

//iOS8之后使用
UIView *fromView = [transitionContext viewForKey:UITransitionContextFromViewKey];
UIView *toView = [transitionContext viewForKey:UITransitionContextToViewKey];

• 获取容器

//获取容器视图
UIView *containerView = [transitionContext containerView];

转场代理

• 导航转场
  From控制器遵守导航代理<UINavigationControllerDelegate>

// 别忘记设置代理对象
self.navigationController.delegate = self;

- (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC {
    CustomTransition *transition = [[CustomTransition alloc] init];
    
    switch (operation) {
        case UINavigationControllerOperationPush:
            transition.style = NSTransitionStylePush;
            break;
        case UINavigationControllerOperationPop:
            transition.style = NSTransitionStylePop;
            break;
        default:
            break;
    }
    
    return transition;
}

• 模态转场
  From控制器遵守模态代理<UIViewControllerTransitioningDelegate>

// 别忘记设置present视图控制器代理对象为From视图控制器
nextVC.transitioningDelegate = self;

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source {
    CustomTransition *transition = [[CustomTransition alloc] init];
    transition.style = NSTransitionStylePresent;
    return transition;
}

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed {
    CustomTransition *transition = [[CustomTransition alloc] init];
    transition.style = NSTransitionStyleDismiss;
    return transition;
}

注意事项

• 目标视图toView要添加到容器视图containerView里。
• 转场类型不同对应的目标视图toView和当前视图fromVC也不同。