修改NavigationBar颜色及样式

#pragma mark - 设置navigation颜色
- (void)setNavigationBarColor {
    UINavigationBar *bar = [UINavigationBar appearance];
    bar.barTintColor = [UIColor whiteColor]; //nav颜色
    bar.tintColor = [UIColor darkGrayColor]; //nav前景色 包括按钮颜色
    [bar setTitleTextAttributes:@{NSForegroundColorAttributeName : [UIColor darkGrayColor]}]; //title颜色
}