求解 自定义一个在StatusBar位置上的UIWindow不能显示

我在一个ViewController 中定义一个在Statusbar上显示自定义的UIwindow 怎么都不能显示出来，不知道为什么？代码如下：

XCode 6.1

 UIWindow * statusWindow = [[UIWindow alloc] initWithFrame:[UIApplication sharedApplication].statusBarFrame]; 

       [statusWindow setWindowLevel:UIWindowLevelAlert + 1]; 

    [statusWindow setBackgroundColor:[UIColor clearColor]]; 

     

    UILabel * statusLabel = [[UILabel alloc] initWithFrame:statusWindow.bounds]; 

    statusLabel.text = @"Loading..."; 

    statusLabel.textColor = [UIColor blueColor]; 

    statusLabel.textAlignment = NSTextAlignmentCenter; 

    statusLabel.backgroundColor = [UIColor blackColor]; 

    [statusWindow setHidden:NO]; 

    [statusWindow setAlpha:1.0f]; 

    [statusWindow addSubview:statusLabel]; 

     

    [statusWindow makeKeyAndVisible];