View got hidden below UINavigationBar iOS 7

问题:

Earlier, I was using iOS 6.1 for my project. Recently I have switched to iOS 7. For, a lot of changes I knew, I updated my code.. But I have observed a strange behavior. My view on every screen gets hidden below navigation bar. Repositioning view solves the problem for iOS7, but creates problems for older iOS versions.

Can anyone explain me, what is the reason and why does it happen?? What has been changed in iOS 7 that's causing this problem??

Any help would be appreciated..

回答1:

Try navigationBar.translucent = NO;, It is YES by default in iOS7.

It is also good to take a look on this part of UINavigationBar documentation:

New behavior on iOS 7. Default is YES. You may force an opaque background by setting the property to NO. If the navigation bar has a custom background image, the default is inferred from the alpha values of the image—YES if it has any pixel with alpha < 1.0 If you send setTranslucent:YES to a bar with an opaque custom background image it will apply a system opacity less than 1.0 to the image. If you send setTranslucent:NO to a bar with a translucent custom background image it will provide an opaque background for the image using the bar's barTintColor if defined, or black for UIBarStyleBlack or white for UIBarStyleDefault if barTintColor is nil.

Edit:

Setting 'navigationBar.translucent' value causes exception if you run project in devices/simulators having older iOS versions.

So you can add a version check like this:

float systemVersion = [[[UIDevice currentDevice] systemVersion] floatValue];
if (systemVersion >= 7.0)
{
    navigationBar.translucent = NO;
}

Another option would be to set:

vc.edgesForExtendedLayout = UIRectEdgeNone;

Swift 3:

vc.edgesForExtendedLayout = []

回答2:

You can stop your views going under the navigation bar, in your viewController:

self.edgesForExtendedLayout = UIRectEdgeNone;

回答3:

Swift 3+:

self.edgesForExtendedLayout = []

回答4:

If you do not need translucent navigation bar in your app you can fix this on iOS7 and iOS6 without code changes.

In storyboard select your navigation controller and then open "Attributes Inspector". Then under "Simulated Metrics" set "Top Bar" to some value but not to "translucent":

Now your views on iOS6 and iOS7 will have the same positioning as before.

回答5:

Point #7 on this list does the trick. You still have to wrap it in iOS 7-checking code like @null's answer:

float systemVersion = [[[UIDevice currentDevice] systemVersion] floatValue];
if (systemVersion >= 7.0) {
    viewController.edgesForExtendedLayout = UIRectEdgeNone;
}

The whole article is useful to those transitioning to iOS 7.

回答6:

Use this property for your VC, in-order to avoid overlap of ur statusbar with your VC Swift :

self.edgesForExtendedLayout = []

Objective C

self.edgesForExtendedLayout = UIRectEdgeNone;

回答7:

Look up this key: UIViewControllerBasedStatusBarAppearance.

It's used in your app's info PLIST file and will come up as:

View controller-based status bar appearance

This will allow you to control the status bar's appearance. There's a bunch of API changes for status bars, go have a look in the documentation for new UIViewController methods such as

- (void)prefersStatusBarHidden;

回答8:

In Swift 2.2, use

self.edgesForExtendedLayout = .None

回答9:

For me the best way for transparent Navigation Bar is to change the shadowImage and backgroundImage of the bar.

navigationController?.navigationBar.isTranslucent = true
navigationController?.navigationBar.backgroundColor = nil
navigationController?.navigationBar.setBackgroundImage(UIImage(named: "navBarBackground")?.resizableImage(withCapInsets: .zero, resizingMode: .stretch), for: .default)  
navigationController?.navigationBar.shadowImage = UIImage()