提取AppDelegate.m中的"RDVTabBarController"第三方框架的方法

提取这个主要是因为，不想让 “AppDelegate.m” 里面有太多的代码，看起来乱。

步骤：

1. 创建一个分类，继承自 AppDelegate 。 

2. 在类.h中写：

/**
 *  设置自定义的tabbar
 *
 *  @return 自定义的tabBarController
 */
- (UIViewController *)setupCustomTabBarController;

3. 在类.m 中写：

@implementation AppDelegate (TabBar)
/**
 *  设置自定义的tabbar
 *
 *  @return 自定义的tabBarController
 */
- (UIViewController *)setupCustomTabBarController
{
    // 第一个
    UIViewController *firstViewController = [[UIViewController alloc] init];
    firstViewController.view.backgroundColor = [UIColor redColor];
    UIViewController *firstNavigationController = [[UINavigationController alloc]
                                                   initWithRootViewController:firstViewController];
    
    // 第二个
    UIViewController *secondViewController = [[UIViewController alloc] init];
    secondViewController.view.backgroundColor = [UIColor orangeColor];
    UIViewController *secondNavigationController = [[UINavigationController alloc]
                                                    initWithRootViewController:secondViewController];
    
    // 第三个
    UIViewController *thirdViewController = [[UIViewController alloc] init];
    thirdViewController.view.backgroundColor = [UIColor greenColor];
    UIViewController *thirdNavigationController = [[UINavigationController alloc]
                                                   initWithRootViewController:thirdViewController];
    
    RDVTabBarController *tabBarController = [[RDVTabBarController alloc] init];
    [tabBarController setViewControllers:@[firstNavigationController, secondNavigationController,
                                           thirdNavigationController]];
    
    [self customizeTabBarForController:tabBarController];
    
    return tabBarController;
}

- (void)customizeTabBarForController:(RDVTabBarController *)tabBarController {
    UIImage *finishedImage = [UIImage imageNamed:@"tabbar_selected_background"];
    UIImage *unfinishedImage = [UIImage imageNamed:@"tabbar_normal_background"];
    NSArray *tabBarItemImages = @[@"first", @"second", @"third"];
    
    NSInteger index = 0;
    for (RDVTabBarItem *item in [[tabBarController tabBar] items]) {
        [item setBackgroundSelectedImage:finishedImage withUnselectedImage:unfinishedImage];
        UIImage *selectedimage = [UIImage imageNamed:[NSString stringWithFormat:@"%@_selected",
                                                      [tabBarItemImages objectAtIndex:index]]];
        UIImage *unselectedimage = [UIImage imageNamed:[NSString stringWithFormat:@"%@_normal",
                                                        [tabBarItemImages objectAtIndex:index]]];
        [item setFinishedSelectedImage:selectedimage withFinishedUnselectedImage:unselectedimage];
        
        index++;
    }
}

- (void)customizeInterface {
    UINavigationBar *navigationBarAppearance = [UINavigationBar appearance];
    
    UIImage *backgroundImage = nil;
    NSDictionary *textAttributes = nil;
    
    if (NSFoundationVersionNumber > NSFoundationVersionNumber_iOS_6_1) {
        backgroundImage = [UIImage imageNamed:@"navigationbar_background_tall"];
        
        textAttributes = @{
                           NSFontAttributeName: [UIFont boldSystemFontOfSize:18],
                           NSForegroundColorAttributeName: [UIColor blackColor],
                           };
    } else {
#if __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_7_0
        backgroundImage = [UIImage imageNamed:@"navigationbar_background"];
        
        textAttributes = @{
                           UITextAttributeFont: [UIFont boldSystemFontOfSize:18],
                           UITextAttributeTextColor: [UIColor blackColor],
                           UITextAttributeTextShadowColor: [UIColor clearColor],
                           UITextAttributeTextShadowOffset: [NSValue valueWithUIOffset:UIOffsetZero],
                           };
#endif
    }
    
    [navigationBarAppearance setBackgroundImage:backgroundImage
                                  forBarMetrics:UIBarMetricsDefault];
    [navigationBarAppearance setTitleTextAttributes:textAttributes];
}