Question

当我在特定的ViewController中时，我正在尝试更改导航栏的图像背景。我的app模型： - appDelegate - tabbarcontroller -viewcontroller1 -navigationBarController -viewcontroller2 -viewcontroller3（*） -viewcontroller4 -viewcontroller5

我已经在appDelegate中实现了这段代码：

static NSMutableDictionary *navigationBarImages = NULL;

    @implementation UINavigationBar(CustomImage)

    + (void)initImageDictionary
    {
        if(navigationBarImages==NULL){
            navigationBarImages=[[NSMutableDictionary alloc] init];
        }   
    }
    - (void)drawRect:(CGRect)rect
    {
        UIColor *color = [UIColor blackColor];
        NSString *imageName=[navigationBarImages objectForKey:[NSValue valueWithNonretainedObject: self]];
        if (imageName==nil) {
            imageName=@"navbar.png";
        }
        UIImage *image = [UIImage imageNamed:imageName];
        [image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
        self.tintColor = color;

    }

    - (void)setImage:(UIImage*)image
    {
        [navigationBarImages setObject:image forKey:[NSValue valueWithNonretainedObject: self]];
    }
    @end

之后，我在viewcontroller2中编写了这段代码：

[UINavigationBar initImageDictionary];

这是工作，我的导航栏就像我希望的那样，但是在我的viewcontroller3中，我写道：

UIImage *navBarLandscape = [UIImage imageNamed:@"navbar.png"];
    [[[self navigationController] navigationBar] setImage:navBarLandscape];

并且它没有做到这一点，我有一个错误，我无法承担：

[UIImage length]：无法识别的选择器发送到实例0x5a58130 2010-11-18 18：02：37.170 finalAudi [1463：307] * 由于未捕获的异常'NSInvalidArgumentException'终止应用程序，原因：' - [UIImage长度]：无法识别的选择器发送到实例0x5a58130'

你有什么想法吗？

关于马球。

Answer 1

在每个viewController的viewDidLoad尝试：

/*  make sure that we set the image to be centered  */ 
/*  you will ahve to make minor adjustments depending on the dimensions of your image.  */
UIImageView *logo = [[UIImageView alloc] initWithFrame:CGRectMake(self.navigationController.navigationBar.frame.size.width/2-75,0,150,
                                                       self.navigationController.navigationBar.frame.size.height-1)];
[logo setImage:[UIImage imageNamed:@"myImage.png"]];
[self.navigationController.navigationBar addSubview:logo];
[self.navigationController.navigationBar sendSubviewToBack:logo];

以及viewWillAppear:和viewDidDisappear:尝试：

/*  This will ensure that if you have a different image for each view that the previous viewController's navBar image wont stay.  */
-(void)viewWillDisappear:(BOOL)animated {logo.hidden = YES;}
-(void)viewWillAppear:(BOOL)animated    {logo.hidden = NO ;}

并确保旋转时图像保持居中：

-(void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    if(((interfaceOrientation == UIInterfaceOrientationLandscapeLeft) || 
    (interfaceOrientation == UIInterfaceOrientationLandscapeRight))){
        [logo setFrame:CGRectMake(self.navigationController.navigationBar.frame.size.width/2-75,0,150,self.navigationController.navigationBar.frame.size.height-1)];
    }else if(((interfaceOrientation == UIInterfaceOrientationPortrait) || 
          (interfaceOrientation == UIInterfaceOrientationPortraitUpsideDown))){
        [logo setFrame:CGRectMake(self.navigationController.navigationBar.frame.size.width/2-80,0,150,self.navigationController.navigationBar.frame.size.height-1)];
    }
}

Answer 2

感谢大家，我能够在appdelegate中解决我的问题：

@implementation UINavigationBar(CustomImage)

+ (void)initAppDelegate
{
    if (applicationDelegate==Nil) {
        applicationDelegate = (finalAudiAppDelegate *)[[UIApplication sharedApplication] delegate];
    }
}
- (void)drawRect:(CGRect)rect
{
    UIColor *color = [UIColor blackColor];
    [[[applicationDelegate backNavBar] objectAtIndex:[applicationDelegate indexBackNavBar]] drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
    self.tintColor = color;
}
@end

我正在使用一个NSMutableArray来存储我的navigationBar的背景图像和一个NSInteger（indexBackNavBar），我可以通过UIApplication sharedApplication访问它们。然后在我的viewcontroller中，我只在viewWillAppear中设置indexBackNavBar = 1，在viewWillDisappear中设置indexBackNavBar = 0。瞧！

Answer 3

如果我理解正确，我会建议查看UINavigationBarDelegate并实现代码以在那里切换导航栏的背景，而不是将其传播到多个viewControllers。

委托具有在推送和弹出新视图之前将被调用的方法，因此从设计角度来看可能会更好

如何在特定的ViewController中手动更改导航栏背景图像？

3 个答案: