iphone - AppDelegate UIWindow addSubView 在不同的 viewController

Question

我正在尝试从 UIViewController 在 AppDelegate 的 UIWindow 中添加一个 UILabel。我就是这样做的:

AppDelegate 代码:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
    // Override point for customization after application launch.
    if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
        self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController_iPhone" bundle:nil] autorelease];
    } else {
        self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController_iPad" bundle:nil] autorelease];
    }



    [self.window makeKeyAndVisible];

    self.window.rootViewController = self.viewController;


    return YES;
}

ViewController 代码:

- (void)viewDidLoad
{

    UILabel *abcd=[[UILabel alloc] initWithFrame:CGRectMake(100.0, 100.0, 200.0, 40.0)];

    abcd.text=@"loading...";

    abcd.backgroundColor=[UIColor clearColor];

    [[[[UIApplication sharedApplication] delegate] window] addSubview:abcd];

    [super viewDidLoad];


}  

但我看到的只是灰色屏幕，没有标签。我可能哪里出错了？

Answer 1

您不能将 UILabel 添加到 UIWindow，您应该添加到 UIViewController。更改此行:

[[[[UIApplication sharedApplication] delegate] window] addSubview:abcd];

为此:

[self.view addSubview:abcd];