ios - 在主窗口上创建一个新的 UIWindow

Question

在我的应用程序中，我想在主 UIWindow 上创建一个新的 UIWindow，我写如下，但它不起作用。首先，我创建一个 UIWindow 作为主窗口，然后将其设置为键和可见，然后创建一个新的 UIWindow 覆盖，但没有任何反应。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.window.backgroundColor = [UIColor redColor];
    ViewController *vc = [[ViewController alloc]initWithNibName:@"ViewController" bundle:nil];
    self.window.rootViewController = vc;
    [self.window makeKeyAndVisible];
    UIWindow *window1 = [[UIWindow alloc] initWithFrame:CGRectMake(0, 0, 320, 320)];
    window1.backgroundColor = [UIColor redColor];
    window1.windowLevel = UIWindowLevelAlert;
    [window1 makeKeyAndVisible];
    return YES;
}

Answer 1

UIWindow *window1 = [[UIWindow alloc] initWithFrame:CGRectMake(0, 0, 320, 320)];
window1.backgroundColor = [UIColor redColor];
window1.windowLevel = UIWindowLevelAlert;
[window1 makeKeyAndVisible];

终于知道为什么不行了，因为window1是一个method var，method执行完就丢失了。所以我为它声明了一个新的@property，如

@property (strong, nonatomic) UIWindow *window2;

和像这样更改代码

UIWindow *window2 = [[UIWindow alloc] initWithFrame:CGRectMake(0, 80, 320, 320)];
window2.backgroundColor = [UIColor redColor];
window2.windowLevel = UIWindowLevelAlert;
self.window2 = window2;
[window2 makeKeyAndVisible];

它有效!