Xamarin Forms DependencyService nullReferenceException

Question

我試圖添加一個圖片從我的手機庫，但不斷得到一個System.Reference，我想從按鈕上按一下我的手機圖庫上傳圖像，它給出了一個nullReferenceException DependencyService。

我的頁面：

InitializeComponent(); 


     Device.OnPlatform(
      Android:() => { 
       new Thickness(0, 20, 0, 0); 
       } 
     ); 

     Image image = new Image(); 

     Button addImage = new Button { Text = "Select Image" }; 
     addImage.Clicked += (sender, args) => 
     { 
      IGalleryImageService galleryService = DependencyService.Get<IGalleryImageService>(); 
      galleryService.ImageSelected += (o, imageSourceEventArgs) => image.Source = imageSourceEventArgs.ImageSource; 
      galleryService.SelectImage(); 

     }; 

     this.Content = new StackLayout 
     { 
      Children = 
      { 
       image, 
       addImage 
      } 
     }; 

Answer 1

你可能忘了加上正確的屬性導出的實現。

你是否在GalleryImageService_Android.cs文件中的命名空間聲明上面有這個？

[assembly: Xamarin.Forms.Dependency (typeof (GalleryImageService_Android))]