title: How to set MFMailComposeViewController navigitaion bar backgroundImage at ios 8.3
body: <p>in <code>AppDelegate</code> <code>didFinishLaunchingWithOptions</code>,</p>
  
  <pre><code>[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];
  [[UINavigationBar appearance] setBackgroundImage:[UIImage imageNamed:@"Topbar"] forBarMetrics:UIBarMetricsDefault];
  </code></pre>
  
  <p>but when i response system email :</p>
  
  <pre><code> MFMailComposeViewController *mc = [[MFMailComposeViewController alloc] init];
   [mc.navigationBar setTintColor:[UIColor whiteColor]];
   [mc.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"Topbar"] forBarMetrics:UIBarMetricsDefault];
  
  [self presentViewController:mc animated:YES completion:^{
           [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent animated:NO];}];
  </code></pre>
  
  <p>but <code>MFMailComposeViewController</code> also is white</p>