How do I update the StatusBar Style as part of a c

问题:

I'm using the iOS 7 UIviewControllerAnimatedTransitioning protocol to present a modal ViewController with a custom animation. The animation works correctly, however, I want the newly presented ViewController to have a different status bar style than the presenting VC.

What I'm seeing is that -(UIStatusBarStyle)preferredStatusBarStyle gets called on the PRESENTING ViewController (several times in fact) and never on the newly presented ViewController. If I remove the custom animation everything with the status bar works as I'd expect.

Is there something special I need to do in my animateTransition function to update the root view controller or something? I've tried manually setting the statusBar with [UIApplication sharedApplication] setStatusBarStyle but it doesn't work (I think because I'm using the ios 7 view controller based status bar styling).

This is my code for animateTransition:

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
    UICollectionViewCell *activeCell;
    if ([self.collectionView.visibleCells containsObject:self.cellForActiveIdeaVC]) {
        activeCell = self.cellForActiveIdeaVC;
    }

    UIView *container = transitionContext.containerView;
    UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIView *fromView = fromVC.view;
    UIView *toView = toVC.view;

    CGRect beginFrame;
    if (activeCell) {
        beginFrame = [container convertRect:activeCell.bounds fromView:activeCell];
    } else {
        beginFrame = CGRectMake(container.width / 2, container.height / 2, 0, 0);
    }

    CGRect endFrame = [transitionContext initialFrameForViewController:fromVC];

    UIView *move = nil;
    if (toVC.isBeingPresented) {
        toView.frame = endFrame;
        move = [toView snapshotViewAfterScreenUpdates:YES];
        move.frame = beginFrame;
    } else {
        if (activeCell) {
            move = [activeCell snapshotViewAfterScreenUpdates:YES];
        } else {
            move = [fromView snapshotViewAfterScreenUpdates:YES];
        }
        move.frame = fromView.frame;
        [fromView removeFromSuperview];
    }
    [container addSubview:move];

    [UIView animateWithDuration:.5
                          delay:0
         usingSpringWithDamping:700
          initialSpringVelocity:15
                        options:0
                     animations:^{
                         move.frame = toVC.isBeingPresented ?  endFrame : beginFrame;
                     }
                     completion:^(BOOL finished) {
                         [move removeFromSuperview];

                         if (toVC.isBeingPresented) {
                             toView.frame = endFrame;
                             [container addSubview:toView];
                         } else {
                             if (self.cellForActiveIdeaVC) {
                                 self.cellForActiveIdeaVC = nil;
                             }
                         }

                         [transitionContext completeTransition:YES];
                     }];
}

Any pointers much appreciated!

回答1:

With iOS 7 custom transitions, it's possible to present a view controller that isn't fullscreen and therefore wouldn't affect the statusbar appearance. You have to explicitly tell iOS that your custom presented view controller will, in fact, control the status bar's appearance.

UIViewController *controllerToPresent = [...]
controllerToPresent.modalPresentationStyle = UIModalPresentationStyleCustom;
controllerToPresent.modalPresentationCapturesStatusBarAppearance = YES;

[self presentViewController:controllerToPresent animated:YES completion:nil];

There's some more information here. Hope that helps!

回答2:

This worked for me:

    [UIView animateWithDuration:0.25
                          delay:0
                        options:UIViewAnimationOptionCurveEaseOut
                     animations:^{
                         _preferredBarStyle = UIStatusBarStyleLightContent;
                         [self setNeedsStatusBarAppearanceUpdate];
                     }];

And then you just have to return this value on the preferredStatusBarStyle method:

- (UIStatusBarStyle) preferredStatusBarStyle {
    return _preferredBarStyle;
}

I hope it helps!