Black bar appears under navigation bar

问题

There are several similar questions which got no answers but were describe vaguely. I have reduced the problem into a very thin application, and added detailed screenshots. I would highly appreciate a solution for this!

The only involved code is one line added to viewDidLoad of the root VC. The purpose of this line is to make the navigation controller opaque:

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.navigationController.navigationBar.translucent = NO;
}

A critical information for this question is that 'Title1' has a prompt in its navigation item, while 'Title2' has not prompt.

I have a storyboard with one navigation controller, one root VC called "Title1", with a segue button which takes to a second VC called "Title2"

---

When pressing the button here:

---

I'm getting this strange screen:

---

When pressing back (Title1), it gets worse (i.e.: the original label of Title1 was pushed up and now not being seen anymore!!!):

Anyone please??

回答1:

Late answer but I stumbled across this problem today and found your question and it doesn't have an accepted answer yet.

I got this error while going from a prompted viewController to a non prompted viewController in storyboard.

I got that black bar just like you.

And to fix:

// In prompted vc
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    UIView.setAnimationsEnabled(false)
    self.navigationItem.prompt = nil
    UIView.setAnimationsEnabled(true)
}

This will remove the prompt instantly before switching viewcontroller.

UPDATE

func prompt() -> String? {
    return nil
}

override func viewWillAppear(animated: Bool) {
    let action = { self.navigationItem.prompt = self.prompt() }

    if self.navigationController?.viewControllers.count <= 1 {
        UIView.performWithoutAnimation(action)
    }
    else {
        action()
    }
}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {        
    UIView.performWithoutAnimation {
        self.navigationItem.prompt = (segue.destinationViewController as? ViewController)?.prompt()
    }
}

回答2:

It appeared as translucent property of UINavigationBar appeared to be messed up with frame other view controllers.

I would recommend following approach.

Create a base view controller from which other view controllers will inherit as follows,

#import "BaseViewController.h"

@interface BaseViewController ()

@end

@implementation BaseViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.navigationController.navigationBar.translucent = NO;
}

other view controllers will inherit above BaseViewController

// interface

#import <UIKit/UIKit.h>
#import "BaseViewController.h"

@interface ViewController : BaseViewController

@end

// implementation

#import "ViewController.h"

@implementation ViewController

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    // Here translucent property is enabled when the view is about to be disappeared.
    // However note that, translucent property needs to be enabled only on those view controllers which has prompt set on their navigation items.
    self.navigationController.navigationBar.translucent = YES;
}

Other view controllers without prompt implementation will work as usual however they also needs to inherit from BaseViewController.

回答3:

The best way to solve this issue is setting the background of the window during push i.e,

let appdelegate = UIApplication.shared.delegate as! AppDelegate
appdelegate.window?.backgroundColor = UIColor.white

回答4:

Seems like Xcode has some issues when changing the navigationBar height since main controller view is not resized accordingly.

I found a solution to do this, not sure it is the best... but it's working.

Just inherit your viewWillAppear and viewWillDisappear methods in your first view controller (the one with a prompt):

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    self.navigationItem.prompt = @"Prompt1";

    [UIView animateWithDuration:UINavigationControllerHideShowBarDuration
                          delay:0.0
                        options: UIViewAnimationOptionCurveEaseOut
                     animations:^{
                         [self.view setFrame:CGRectMake(0, 94, 320, 386)];
                     }
                     completion:^(BOOL finished){
                     }];

}

- (void) viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];

    // Sets prompt to nil
    self.navigationItem.prompt = nil;

    [UIView animateWithDuration:UINavigationControllerHideShowBarDuration
                          delay:0.0
                        options: UIViewAnimationOptionCurveEaseOut
                     animations:^{
                         [self.view setFrame:CGRectMake(0, 64, 320, 416)];
                     }
                     completion:^(BOOL finished){
                     }];
}

I didn't focus on frame size (it's for 3,5" iPhone frame sizes). You must calculate this size or you might have some issues with larger screens.

来源：https://stackoverflow.com/questions/21073865/black-bar-appears-under-navigation-bar