UIViewController * releaseVC = [[UIViewController alloc] init];

 releaseVC.view.backgroundColor=RGBA(222,222,222,0.85);

  releaseVC.modalPresentationStyle = UIModalPresentationOverCurrentContext;

  [self presentViewController:releaseVC animated:YES completion:nil];

注意UIViewController的modalPresentationStyle要设置成UIModalPresentationOverCurrentContext