设置控件全局显示样式 appearance

+ (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。

支持UIAppearance协议的类可以访问appearance selector ,它为receiver返回appearance proxy，我么可以给proxy发一些消息，诸如setTintColor:等

但是它并不是支持所有的UI类。下面列出它支持的类

　　1.UIActivitiIndicatorView

　　2.UIBarButtonItem

　　3.UIBarItem

　　4.UINavgationBar

　　5.UIPopoverControll

　　6.UIProgressView

　　7.UISearchBar

　　8.UISegmentControll 

　　9.UISlider

　　10.UISwitch

　　11.UITabBar

　　12.UITabBarItem

　　13.UIToolBar

　　14.UIView

　　15.UIViewController

 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];

4.UIBarbutton

注意：UIBarbutton有leftBarButton，rightBarButton和backBarButton，其中backBarButton由于带有箭头，需要单独设置。

barButton背景设置是ios6.0及以后的，而backbutton是ios5.0及以后的，这里要注意！

代码如下：

    //修改导航条上的UIBarButtonItem

    UIBarButtonItem *appearance = [UIBarButtonItem appearanceWhenContainedIn:[UINavigationBar class], nil];

    //设置导航栏的字体包括backBarButton和leftBarButton，rightBarButton的字体

    NSDictionary *textAttributes = @{UITextAttributeFont: [UIFontsystemFontOfSize:18],

                                     UITextAttributeTextColor: [UIColorblueColor],

                                     UITextAttributeTextShadowColor: [UIColorwhiteColor],

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

    [appearance setTitleTextAttributes:textAttributes forState:1];//forState为0时为下正常状态，为1时为点击状态。

    //修改leftBarButton，rightBarButton背景效果

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

                          forState:UIControlStateNormal

                             style:UIBarButtonItemStyleBordered

                        barMetrics:UIBarMetricsDefault];

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

                          forState:UIControlStateHighlighted

                             style:UIBarButtonItemStyleBordered

                        barMetrics:UIBarMetricsDefault];

    //backBarButton需要单独设置背景效果。只能在ios6.0以后才能用

    [appearance setBackButtonBackgroundImage:[UIImage imageNamed:@"nav_bg.png"]

                                    forState:0

                                  barMetrics:UIBarMetricsDefault];

    [appearance setBackButtonBackgroundImage:[UIImage imageNamed:@"work.png"]

                                    forState:1

                                  barMetrics:UIBarMetricsDefault];

    [appearance setBackButtonTitlePositionAdjustment:UIOffsetMake(2, -1)

                                       forBarMetrics:UIBarMetricsDefault];

5.工具栏（UIToolbar）

   UIToolbar *appearance = [UIToolbar appearance];

    //样式和背景二选一即可，看需求了

    //样式（黑色半透明，不透明等）设置

    [appearance setBarStyle:UIBarStyleBlackTranslucent];

    //背景设置

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

                forToolbarPosition:UIToolbarPositionAny

                        barMetrics:UIBarMetricsDefault];