UINavigationController中的setAlpha

Question

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

#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，这里是该结果的屏幕截图：正如你可以看到alpha没有改变。

任何想法？我把这个放在错误的地方吗？

Answer 1

问题是，self.navigationItem.titleView不给你任何东西。该属性可以由您设置以替换屏幕截图中显示的默认标签。但是，没有API设计用来做你想做的事情。

问题是：你想达到什么目的？如果你想要或者改变它的色调，你可以使它变成半透明的。改变文字不透明度并不太容易。你可能摆弄控制器的UINavigationBar的子视图，但我不想这样做。