presentViewController--尝试在__上呈现__，__其视图不在窗口层次结构中

Question

我正在尝试使用UIImagePickerControl执行presentViewController以显示标准Camera Roll照片选取器。这在我的大部分应用程序中都是端到端的。它不起作用的地方是当我想在已经呈现的viewController内使用imagePicker的时候;无法呈现呈现相册的视图。

基本思想是我试图访问窗口对象上的rootViewController，或者应用程序委托的持久tabBarController（这是rootViewController）;这两个例子都是希望永远存在的顶级项目的例子。只是使用“自我”，否则最终会作为呈现它的局部视图。

有一个可靠的方式presentViewController内已经呈现的视图？

dispatch_async(dispatch_get_main_queue(),^{ 
    // 1. attempt that works well elsewhere in app 
    [((AppDelegate*)[[UIApplication sharedApplication] delegate]).tabBarController presentViewController:self.imagePickerController animated:YES completion:nil]; 

    // 2. this does nothing, no crash or action (_UIAlertShimPresentingViewController) 
    [[[UIApplication sharedApplication] keyWindow].rootViewController presentViewController:self.imagePickerController animated:YES completion:nil]; 

    // 3. attempt off related internet suggestion, nothing happens 
    UIViewController *topController = [UIApplication sharedApplication].keyWindow.rootViewController; 
    while (topController.presentedViewController) { 
     topController = topController.presentedViewController; 
    } 
    [topController presentViewController:self.imagePickerController animated:YES completion:nil]; 

}); 

Answer 1

因为presentViewController意为模式的介绍，我不认为这是有可能在同一UIWindow同时出示第二模式。但是，您可以添加新的UIWindow并将其呈现在那里。

originalWindow = [[[UIApplication sharedApplication] keyWindow]; 
tempWindow = [[UIWindow alloc] init]; 
UIViewController *controller = [[UIViewController alloc] init]; 
tempWindow.rootViewController = controller; 
[tempWindow makeKeyAndVisible]; 
[controller presentViewController:self.imagePickerController animated:YES completion:nil]; 

你需要添加像这样在你的回应图像选择器的返回：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info { 
    // Process the result and then... 
    [self cleanupWindow]; 
} 

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker { 
    [self cleanupWindow]; 
} 

- (void)cleanupWindow { 
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(madeKeyWindow:) name:UIWindowDidBecomeKeyNotification object:nil]; 
    [originalWindow makeKeyAndVisible]; 
} 

- (void)madeKeyWindow:(NSNotification *)notification { 
    [tempWindow removeFromSuperview]; 
    tempWindow = nil; 
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIWindowDidBecomeKeyNotification object:nil]; 
}