Xamarin Forms DependencyService nullReferenceException

Question

我试图添加一个图片从我的手机库，但不断得到一个System.Reference，我想从按钮上按一下我的手机图库上传图像，它给出了一个nullReferenceException DependencyService。

我的页面：

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

你可能忘了加上正确的属性导出的实现。

你是否在GalleryImageService_Android.cs文件中的命名空间声明上面有这个？

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