UINavigationBar appearance 无效原因分析

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    // Override point for customization after application launch.

    [[UINavigationBar appearance] setBarTintColor: [UIColor cyanColor]];

    

    return YES;

}

 这样就可以了

iOS5及其以后提供了一个比较强大的工具UIAppearance，我们通过UIAppearance设置一些UI的全局效果，这样就可以很方便的实现UI的自定义效果又能最简单的实现统一界面风格，它提供如下两个方法。

+ (id)appearance

这个方法是统一全部改，比如你设置UINavBar的tintColor，你可以这样写：[[UINavigationBar appearance] setTintColor:myColor];

+ (id)appearanceWhenContainedIn:(Class <>)ContainerClass,...

这个方法可设置某个类的改变：例如：设置UIBarButtonItem 在UINavigationBar、UIPopoverController、UITabbar中的效果。就可以这样写

[[UIBarButtonItem appearanceWhenContainedIn:[UINavigationBar class], [UIPopoverController class],[UITabbar class] nil] setTintColor:myPopoverNavBarColor];

请注意＊使用appearance设置UI效果最好采用全局的设置，在所有界面初始化前开始设置，否则可能失效。

 具体UI外观修改如下：

1.修改导航栏背景

代码如下：

    UINavigationBar * appearance = [UINavigationBar appearance];

    UIImage *navBackgroundImg =[UIImage imageNamed:@"navBg.png”];

    

    [appearance setBackgroundImage:navBackgroundImgforBarMetrics:UIBarMetricsDefault];

2.标签栏（UITabbar）

代码如下：

    UITabBar *appearance = [UITabBar appearance];

    //设置背景图片

    [appearance setBackgroundImage:[UIImage imageNamed:@"tabbar_bg.png"]];

    //门置选择item的背景图片

    UIImage * selectionIndicatorImage =[[UIImageimageNamed:@"tabbar_slider"]resizableImageWithCapInsets:UIEdgeInsetsMake(4, 0, 0,0)] ;

    [appearance setSelectionIndicatorImage:selectionIndicatorImage];

3.分段控件（UISegmentControl）

代码如下：

    UISegmentedControl *appearance = [UISegmentedControl appearance];

    

    //Segmenteg正常背景

    [appearance setBackgroundImage:[UIImage imageNamed:@"Segmente.png"]

                          forState:UIControlStateNormal

                        barMetrics:UIBarMetricsDefault];

    

    //Segmente选中背景

    [appearance setBackgroundImage:[UIImage imageNamed:@"Segmente_a.png"]

                          forState:UIControlStateSelected

                        barMetrics:UIBarMetricsDefault];

    

    //Segmente左右都未选中时的分割线

    //BarMetrics表示navigation bar的状态，UIBarMetricsDefault 表示portrait状态（44pixel height），UIBarMetricsLandscapePhone 表示landscape状态（32pixel height）

    

    [appearance setDividerImage:[UIImage imageNamed:@"Segmente_line.png"]

            forLeftSegmentState:UIControlStateNormal

              rightSegmentState:UIControlStateNormal

                     barMetrics:UIBarMetricsDefault];

    

    [appearance setDividerImage:[UIImage imageNamed:@"Segmente_line.png"]

            forLeftSegmentState:UIControlStateSelected

              rightSegmentState:UIControlStateNormal

                     barMetrics:UIBarMetricsDefault];

    

    [appearance setDividerImage:[UIImage imageNamed:@"Segmente_line.png"]

            forLeftSegmentState:UIControlStateNormal

              rightSegmentState:UIControlStateSelected

                     barMetrics:UIBarMetricsDefault];

    

    //字体

    NSDictionary *textAttributes1 = @{UITextAttributeFont: [UIFont systemFontOfSize:18],

                                     UITextAttributeTextColor: [UIColor blueColor],

                                     UITextAttributeTextShadowColor: [UIColor whiteColor],

                                     UITextAttributeTextShadowOffset: [NSValuevalueWithCGSize:CGSizeMake(1, 1)]};

    

    [appearance setTitleTextAttributes:textAttributes1 forState:1];

    

    NSDictionary *textAttributes2 = @{UITextAttributeFont: [UIFont systemFontOfSize:18],

                                     UITextAttributeTextColor: [UIColor whiteColor],

                                     UITextAttributeTextShadowColor: [UIColor blackColor],

                                     UITextAttributeTextShadowOffset: [NSValuevalueWithCGSize:CGSizeMake(1, 1)]};

    

    [appearance setTitleTextAttributes:textAttributes2 forState:0];