全局设置NavigationBar样式

建议写进UINavigationBar的Category便于不同项目复用

    [[UINavigationBar appearance] setShadowImage:[[UIImage alloc] init]]; // 隐藏底部线条

    [UINavigationBar appearance].titleTextAttributes = @{NSForegroundColorAttributeName : [UIColor whiteColor]}; // 设置title 颜色

    [UINavigationBar appearance].backIndicatorImage = 
    [UINavigationBar appearance].backIndicatorTransitionMaskImage =
    [UIImage templateImageNamed:@"nav_bar_back_icon_white"];

    [[UINavigationBar appearance] setBarTintColor:MMA_BLACK(1)];
    [[UINavigationBar appearance] setTintColor:[UIColor whiteColor]];
    // hide title of back button
    [[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60)
                                                         forBarMetrics:UIBarMetricsDefault];

    NSShadow *clearShadow = [[NSShadow alloc] init];
    clearShadow.shadowColor = [UIColor clearColor];
    clearShadow.shadowOffset = CGSizeMake(0, 0);

    UIColor *normalTitleColor = [UIColor whiteColor];
    UIColor *highlightedTitleColor = [UIColor whiteColor];
    [[UIBarButtonItem appearance] setTitleTextAttributes:@{
                                                           NSForegroundColorAttributeName : normalTitleColor,
                                                           NSShadowAttributeName : clearShadow
                                                           } forState:UIControlStateNormal];
    [[UIBarButtonItem appearance] setTitleTextAttributes:@{
                                                           NSForegroundColorAttributeName : highlightedTitleColor,
                                                           NSShadowAttributeName : clearShadow
                                                           } forState:UIControlStateHighlighted];
    [[UIBarButtonItem appearance] setTintColor:[UIColor whiteColor]];
    [[UIToolbar appearance] setBarTintColor:[UIColor whiteColor]];