设置导航栏主题＋iOS6 & iOS7 适配

/**
 *  设置导航栏按钮主题
 */
+ (void)setupBarButtonItemTheme
{
    UIBarButtonItem *item = [UIBarButtonItem appearance];
    
    // 设置背景
    if (!iOS7) {
        [item setBackgroundImage:[UIImage imageWithName:@"navigationbar_button_background"] forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
        [item setBackgroundImage:[UIImage imageWithName:@"navigationbar_button_background_pushed"] forState:UIControlStateHighlighted barMetrics:UIBarMetricsDefault];
        [item setBackgroundImage:[UIImage imageWithName:@"navigationbar_button_background_disable"] forState:UIControlStateDisabled barMetrics:UIBarMetricsDefault];
    }
    
    // 设置文字属性
    NSMutableDictionary *textAttrs = [NSMutableDictionary dictionary];
    textAttrs[UITextAttributeTextColor] = iOS7 ? [UIColor orangeColor] : [UIColor grayColor];
    textAttrs[UITextAttributeTextShadowOffset] = [NSValue valueWithUIOffset:UIOffsetZero];
    textAttrs[UITextAttributeFont] = [UIFont systemFontOfSize:iOS7 ? 14 : 12];
    [item setTitleTextAttributes:textAttrs forState:UIControlStateNormal];
    [item setTitleTextAttributes:textAttrs forState:UIControlStateHighlighted];
}

/**
 *  设置导航栏主题
 */
+ (void)setupNavBarTheme
{
    // 取出appearance对象
    UINavigationBar *navBar = [UINavigationBar appearance];
    
    // 设置背景
    if (!iOS7) {
        [navBar setBackgroundImage:[UIImage imageWithName:@"navigationbar_background"] forBarMetrics:UIBarMetricsDefault];
        [UIApplication sharedApplication].statusBarStyle = UIStatusBarStyleBlackOpaque;
    }
    
    // 设置标题属性
    NSMutableDictionary *textAttrs = [NSMutableDictionary dictionary];
    textAttrs[UITextAttributeTextColor] = [UIColor blackColor];
    textAttrs[UITextAttributeTextShadowOffset] = [NSValue valueWithUIOffset:UIOffsetZero];
    textAttrs[UITextAttributeFont] = [UIFont boldSystemFontOfSize:19];
    [navBar setTitleTextAttributes:textAttrs];
}