How to adjust color of navigation bar in qlpreviewcontroller

Question

Can I customize the color of the navigation bar in QlPreviewController?

I tried to follow

[[UINavigationBar appearanceWhenContainedIn: [QLPreviewController class], nil] setBarTintColor: [UIColor redColor]];

but that will not work.

Thanks.

Answer 1

Yes, there is an error with barTintColor in QLPreviewController for iOS 11 if you show it throughpresentViewController: animated:

Here is my solution, use setBackgroundImage: with a 1x1 image instead of setBarTintColor:

[[UINavigationBar appearanceWhenContainedInInstancesOfClasses:@[[QLPreviewController class]]] 
    setBackgroundImage:[UIImage imageWithColor:[UIColor redColor]]
 forBarMetrics:UIBarMetricsDefault];

imageWithColor: - UIImage, 1x1 ( ):

+ (UIImage *)imageWithColor:(UIColor *)color {
    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
    const CGFloat alpha = CGColorGetAlpha(color.CGColor);
    const BOOL opaque = alpha == 1;
    UIGraphicsBeginImageContextWithOptions(rect.size, opaque, 0);
    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;
}

iOS, :

if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"11.0")) {
[[UINavigationBar appearance... 
setBackgroundImage:[UIImage imageWithColor:...]
     forBarMetrics:UIBarMetricsDefault];
    }

SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO:

#define SYSTEM_VERSION_EQUAL_TO(v)                  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedSame)
#define SYSTEM_VERSION_GREATER_THAN(v)              ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedDescending)
#define SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(v)  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN(v)                 ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN_OR_EQUAL_TO(v)     ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedDescending)

Answer 2

! . Swift 4 .

let navbar = UINavigationBar.appearance(whenContainedInInstancesOf: [QLPreviewController.self])
navbar.setBackgroundImage(self.imageWithColor(color: UIColor.red), for: UIBarMetrics.default)

:

func imageWithColor(color: UIColor) -> UIImage {
    let rect = CGRect(x: 0.0, y: 0.0, width: 1.0, height: 1.0)
    let alpha = color.cgColor.alpha
    let opaque = alpha == 1
    UIGraphicsBeginImageContextWithOptions(rect.size, opaque, 0)
    let context = UIGraphicsGetCurrentContext()
    context?.setFillColor(color.cgColor)
    context?.fill(rect)

    return UIGraphicsGetImageFromCurrentImageContext()!
}

Answer 3

, , - , , QLPreviewController. , QLPreviewController , UINavigationController, ViewController . , , viewDidLoad. , QLPreviewController . , viewWillAppear QLPreviewController :

public override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    if let nc = self.children.first as? UINavigationController {
        // your customization code goes here
        nc.navigationBar.tintColor = .yellow
    }
}

Answer 4

,

[[Appearance of UINavigationBar] setBarTintColor: # your color #];