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要設置成UIModalPresentationOverCurrentContext
