为什么我未能获得FromVC和ToVC与[transitionContext viewControllerForKey：UITransitionContextFromViewKey]

Question

我得到了一个问题：

当我试图重写方法startInteractiveTransition:我想救transitionContext，并获取来自transitionContext FromVC和ToVC但失败了， 我不知道为什么？任何人有想法？

这里是代码：

-(void)startInteractiveTransition:(id<UIViewControllerContextTransitioning>)transitionContext 
{ 
    self.transitionContext = transitionContext; 
    id<UIViewControllerContextTransitioning> transitionContext01 = self.transitionContext; 
    if (self.transitionContext) { 
     NSLog(@"start里为空"); 
    }else 
    { 
     NSLog(@"start里不为空"); 
    } 
    NSLog(@"执行了start"); 
    UIViewController * fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewKey]; 
    if (fromVC) { 
     NSLog(@"start里fromVC为空"); 
    }else 
    { 
     NSLog(@"start里fromVC不为空"); 
    } 
    UIViewController * toVC = [transitionContext viewControllerForKey:UITransitionContextToViewKey]; 
    if (toVC) { 
     NSLog(@"start里toVC为空"); 
    }else 
    { 
     NSLog(@"start里toVC不为空"); 
    } 
    [[transitionContext containerView] bringSubviewToFront:fromVC.view]; 
    toVC.view.alpha = self.behindViewAlpha; 
} 

下面是截图： screenshot

Answer 1

通过自己 不UITransitionContextToViewKey 但UITransitionContextToViewControllerKey

找到issur