iOS统一设置导航栏图片

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

  // 自定义UIBarButtonItem返回按钮背景图片
    UIImage *backButton = [[UIImage imageNamed:@"top_back"] resizableImageWithCapInsets:UIEdgeInsetsMake(0, 25.0, 0, 5.0)];
    UIImage *backButtonHighlighted = [[UIImage imageNamed:@"top_back"] resizableImageWithCapInsets:UIEdgeInsetsMake(0, 25.0, 0, 5.0)];
    [[UIBarButtonItem appearance] setBackButtonBackgroundImage:backButton forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
    [[UIBarButtonItem appearance] setBackButtonBackgroundImage:backButtonHighlighted forState:UIControlStateHighlighted barMetrics:UIBarMetricsDefault];

}