UINavigationController 中的 setAlpha

Question

我想在我的 UINavigationController 中设置 titleView 的 alpha。这是这个类的代码：

#import "FAQNavigationController.h"


@implementation FAQNavigationController

/*
 // The designated initializer.  Override if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad.
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    if ((self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])) {

    }
    return self;
}
*/


// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {

 self.navigationItem.titleView.alpha = 0.5;


    [super viewDidLoad];
}


/*
// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
*/

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}


- (void)dealloc {
    [super dealloc];
}


@end

此外，这是该结果的屏幕截图：如您所见，alpha 没有改变。

有什么想法吗？我是不是放错地方了？

Answer 1

问题是self.navigationItem.titleView 没有给你任何东西。您可以设置该属性以替换屏幕截图中显示的默认标签。但是，没有任何 API 可以满足您的需求。

问题是：你想达到什么目标？如果需要，您可以使条形图半透明，或更改其色调。更改文本的不透明度并不容易。您可以摆弄控制器的 UINavigationBar 的子视图，但我会避免这样做。