如何从Xamarin.ios中的图库中选择图像

Question

我想从Gallery加载一个图像并将其显示在UIImageView上。

我试着像Xamarin食谱中的样本那样做，但我得到的只是null。

https://developer.xamarin.com/recipes/ios/media/video_and_photos/choose_a_photo_from_the_gallery/

我的代码到目前为止：

public partial class ViewController : UIViewController
    {
    UIImagePickerController imagePicker;
    UIButton choosePhotoButton;
UIImageView imageView;

public ViewController(IntPtr handle) : base(handle)
{
}

public ViewController()
{
}

public override void ViewDidLoad()
{
    base.ViewDidLoad();
    Title = "Wähle Bild aus:";
    View.BackgroundColor = UIColor.White;

    imageView = new UIImageView(new CGRect(10, 150, 300, 300));
    Add(imageView);

    choosePhotoButton = UIButton.FromType(UIButtonType.RoundedRect);
    choosePhotoButton.Frame = new CGRect(10, 80, 100, 40);
    choosePhotoButton.SetTitle("Picker", UIControlState.Normal);
    choosePhotoButton.TouchUpInside += (s, e) =>
    {
        imagePicker = new UIImagePickerController();

        imagePicker.SourceType = UIImagePickerControllerSourceType.PhotoLibrary;
        imagePicker.MediaTypes = UIImagePickerController.AvailableMediaTypes(UIImagePickerControllerSourceType.PhotoLibrary);

        imagePicker.FinishedPickingMedia += Handle_FinishedPickingMedia;
        imagePicker.Canceled += Handle_Canceled;

        NavigationController.PresentModalViewController(imagePicker, true);

    };

    View.Add(choosePhotoButton);

}


private void Handle_Canceled(object sender, EventArgs e)
{
    imagePicker.DismissModalViewController(true);
}

protected void Handle_FinishedPickingMedia(object sender, UIImagePickerMediaPickedEventArgs e)
{
    bool isImage = false;
    switch (e.Info[UIImagePickerController.MediaType].ToString())
    {
        case "public.image":
            Console.WriteLine("Image selected");
            isImage = true;
            break;
        case "public.video":
            Console.WriteLine("Video selected");
            break;
    }

    // get common info (shared between images and video)
    NSUrl referenceURL = e.Info[new NSString("UIImagePickerControllerReferenceUrl")] as NSUrl;
    if (referenceURL != null)
        Console.WriteLine("Url:" + referenceURL.ToString());

    // if it was an image, get the other image info
    if (isImage)
    {
        // get the original image
        UIImage originalImage = e.Info[UIImagePickerController.OriginalImage] as UIImage;
        if (originalImage != null)
        {
            // do something with the image
            imageView.Image = originalImage; // display
        }

        UIImage editedImage = e.Info[UIImagePickerController.EditedImage] as UIImage;
        if (editedImage != null)
        {
            // do something with the image
            Console.WriteLine("got the edited image");
            imageView.Image = editedImage;
        }
    } 

    // dismiss the picker
    imagePicker.DismissModalViewController(true);
}

我在这一行得到零：NavigationController.PresentModalViewController(imagePicker, true);

我做错了什么？

Answer 1

看来你没有使用UINavigationController，所以改变：

NavigationController.PresentModalViewController(imagePicker, true);

至：

PresentModalViewController(imagePicker, true);

注意：自ios6起，PresentModalViewController已弃用，因此您可以更改要使用的代码：

PresentViewControllerAsync(imagePicker, true);

要么：

PresentViewController(imagePicker, true, () => {
});