C# Xamarin Android-类型或名称空间；上下文“；找不到

我正在学习Xamarin教程。当我在Android项目中使用“Context”类时，VisualStudio抛出一个错误。默认情况下，这个类不应该包含在我的Android应用程序中吗

此外，我在一个名为“Portable”的可移植类库中定义了一个名为“IStreamLoader”的接口，并在我的Android项目中添加了对“Portable”的引用。但在我的Android项目中引用“IStreamLoader”会引发另一个错误

这两个错误相关吗

错误

CS0246  The type or namespace name 'IStreamLoader' could not be found (are you missing a using directive or an assembly reference?)

CS0246  The type or namespace name 'Context' could not be found (are you missing a using directive or an assembly reference?)

CS0246  The type or namespace name 'Context' could not be found (are you missing a using directive or an assembly reference?)

using System.Linq;
using Android.App;
using Android.OS;

namespace MyTunes
{
    [Activity(Label = "My Tunes", MainLauncher = true)]
    public class MainActivity : ListActivity
    {
        protected async override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            var data = await SongLoader.Load();

            ListAdapter = new ListAdapter<Song>() {
                DataSource = data.ToList(),
                TextProc = s => s.Name,
                DetailTextProc = s => s.Artist + " - " + s.Album
            };
        }
    }

    public class StreamLoader : IStreamLoader
    {
        private readonly Context context;

        public StreamLoader(Context context)
        {
            this.context = context;
        }
        public Stream GetStreamForFilename(string filename)
        {
            return context.Assets.Open(filename);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace Portable
{
    public interface IStreamLoader
    {
        System.IO.Stream GetStreamForFilename(string filename);
    }
}

MyTunes.Droid\MainActivity.cs

CS0246  The type or namespace name 'IStreamLoader' could not be found (are you missing a using directive or an assembly reference?)

CS0246  The type or namespace name 'Context' could not be found (are you missing a using directive or an assembly reference?)

CS0246  The type or namespace name 'Context' could not be found (are you missing a using directive or an assembly reference?)

using System.Linq;
using Android.App;
using Android.OS;

namespace MyTunes
{
    [Activity(Label = "My Tunes", MainLauncher = true)]
    public class MainActivity : ListActivity
    {
        protected async override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            var data = await SongLoader.Load();

            ListAdapter = new ListAdapter<Song>() {
                DataSource = data.ToList(),
                TextProc = s => s.Name,
                DetailTextProc = s => s.Artist + " - " + s.Album
            };
        }
    }

    public class StreamLoader : IStreamLoader
    {
        private readonly Context context;

        public StreamLoader(Context context)
        {
            this.context = context;
        }
        public Stream GetStreamForFilename(string filename)
        {
            return context.Assets.Open(filename);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace Portable
{
    public interface IStreamLoader
    {
        System.IO.Stream GetStreamForFilename(string filename);
    }
}

试试这个：

using Android.Content;

---

哇，是的，修复了“上下文”错误，谢谢！您知道我的“IStreamLoader”引用可能失败的原因吗？请尝试使用Portable或公共类StreamLoader:Portable.IStreamLoader呃，显然Portable\IStreamLoader.cs命名空间必须设置为解决方案名称，而不是项目名称。尽管您的上述解决方案也有效。