改变导航栏颜色，字体等

[[UIBarButtonItem appearance] setTintColor:[UIColor whiteColor]];
    [[UINavigationBar appearance] setTitleTextAttributes:@{NSFontAttributeName:[UIFont boldSystemFontOfSize:18]}];
    [[UINavigationBar appearance] setBackgroundImage:[self createImageWithColor:[UIColor colorWithRed:236.0/255.0 green:66.0/255.0 blue:67.0/255.0 alpha:1.0]] forBarMetrics:UIBarMetricsDefault];

-(UIImage*)createImageWithColor:(UIColor*)color
{
    CGRect rect=CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);
    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return theImage;
}