Handling In-Call Status Bar with Custom Modal Presentation

问题

The Problem

I've noticed some strange behavior when presenting a UINavigationController (with a root view controller, already pushed, naturally) with UIViewControllerAnimatedTransitioning during a phone call.

• If the in-call status bar is enabled after the the navigation controller is presented, the navigation controller shifts its view down as expected. But when the call is ended, the controller does not shift its view back up, leaving a 20p gap under the status bar.
• If the in-call status bar is enabled before presenting the controller, the controller does not account for the status bar at all, leaving 4p of the 44p-high navigation bar peeking out from under the 40p status bar. When the call is ended, the controller shifts its view down to accommodate the normal 20p status bar.

*note: this was tested on the simulator, due to the ease of enabling/disabling the in-call status bar, but testers have observed this phenomenon on actual phones.

My (Partial) Workaround

I hacked around the issue by adjusting the frame of the controller during presentation, if the status bar was an abnormal height:

@interface CustomAnimationController : NSObject <UIViewControllerAnimatedTransitioning>
@end

@implementation CustomAnimationController

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
    UIViewController *toController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIView *container = [transitionContext containerView];

    CGRect frame = [transitionContext finalFrameForViewController:toController];
    if (CGRectEqualToRect(frame, CGRectZero))
    {
        // In my experience, the final frame is always a zero rect, so this is always hit
        UIEdgeInsets insets = UIEdgeInsetsZero;
        // My "solution" was to inset the container frame by the difference between the 
        // actual status bar height and the normal status bar height
        insets.top = CGRectGetHeight([UIApplication sharedApplication].statusBarFrame) - 20;
        frame = UIEdgeInsetsInsetRect(container.bounds, insets);
    }

    toController.view.frame = frame;
    [container addSubview:toController.view];

    // Perform whiz-bang animation here
}    

@end

This solution ensures that the navigation bar is below the status bar, but the navigation controller still fails to shift itself back up when the call is ended. So the app is at least usable, but there is an ugly 20p gap above the navigation bar after a call ends.

Is There a Better Way?

Am I missing some critical step to ensure that the navigation controller accounts for the in-call status bar on its own? It works just fine when presented with the built-in modal presentation style.

In my opinion this smacks of a UIKit bug — after all, the navigation controller seems to receive the UIApplicationWillChangeStatusBarFrameNotification (see second point of The Problem). If anyone else has encountered this problem and has found a better way, I would greatly appreciate a solution.

回答1:

I have spent far too much time on over coming the status bar height issue and have come up with a general solution that works for me and I think will work for your situation as well.

First, a couple things that are odd about the status bar.

1. It's normally 20 points tall and the screen is normally 568 points tall

2. While "in-call", the status bar is 40 points high and the screen is 548 points tall

3. While the status bar is hidden, the status bar is 0 points tall and the screen is 568 points tall

If the status bar changes but you don't update the height of the screen then the calculations will be off, and this can be seen in some pretty big name (and even default) applications.

So, the solution that I've come up with is two fold: 1. Create a macro to get the adjusted screen height 2. Register a notification to update the view when the status bar changes.

Here are the macros, I'd recommend putting these in your prefix file

#define kScreenWidth     [UIScreen mainScreen].bounds.size.width
#define kStatusBarHeight (([[UIApplication sharedApplication] statusBarFrame].size.height == 20.0f) ? 20.0f : (([[UIApplication sharedApplication] statusBarFrame].size.height == 40.0f) ? 20.0f : 0.0f))
#define kScreenHeight    (([[UIApplication sharedApplication] statusBarFrame].size.height > 20.0f) ? [UIScreen mainScreen].bounds.size.height - 20.0f : [UIScreen mainScreen].bounds.size.height)

Additionally, here's the notification center call that I've found works for me 100% of the time the status bar changes.

NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
[nc addObserver:self.view selector:@selector(layoutSubviews) name:UIApplicationWillChangeStatusBarFrameNotification object:nil];

回答2:

I had the same issue and the problem was with the view that I was presenting which was automatically adjusted by 20pt because of in-call bar. However since I insert the view into container, I had to reset the frame to match container's bounds.

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
    UIView* destinationView = [transitionContext viewForKey:UITransitionContextToViewKey];
    UIView* container = transitionContext.containerView;

    // Make sure destination view matches container bounds
    // This is necessary to fix the issue with in-call bar
    // which adjusts the view's frame by 20pt.
    destinationView.frame = container.bounds;

    // Add destination view to container
    [container insertSubview:destinationView atIndex:0];

    // [reducted]
}

回答3:

Just set the frame in layoutSubviews as it is called when the status bar height changes. In general as a rule of thumb, do all frame setting in layoutSubviews only.

回答4:

Here is a workaround I put in my app delegate that fixed the problem for me:

- (void)application:(UIApplication *)application willChangeStatusBarFrame:(CGRect)newStatusBarFrame
{
    if (newStatusBarFrame.size.height < 40) {
        for (UIView *view in self.window.subviews) {
            view.frame = self.window.bounds;
        }
    }
}

回答5:

I had the same issue and I fixed it by call update frame view, so i get height status bar. My problem was solved.

 UIView *toViewSnapshot = [toView resizableSnapshotViewFromRect:toView.frame afterScreenUpdates:YES withCapInsets:UIEdgeInsetsZero];

来源：https://stackoverflow.com/questions/22052700/handling-in-call-status-bar-with-custom-modal-presentation