java - 来自 Eclipse 库项目的 Xamarin 绑定(bind)服务 -> InvalidCastException

Question

我是 Xamarin 的新手，我尝试构建一个 Xamarin.Forms 应用程序，该应用程序使用特定扫描仪的 API。 这个 API 来自一个 Android java 项目，我创建了一个 Eclipse Library Project就像 Xamarin 上描述的那样。 所以我现在想做的是从 Eclipse 库项目绑定(bind)这个服务，但在这里我总是得到 invalidCastException。

[assembly: Xamarin.Forms.Dependency(typeof(PlustecDocumentScanner))]
namespace DemoApplication.Droid.Plustec {
  class PlustecDocumentScanner : IDocumentScanner {
    private IPlkScanService _plcScanService;
    private PlkScanCallBack _scanCallBack;
    private PlkSystemCallBack _systemCallBack;
    private IServiceConnection _scanServiceConnection;

    public bool ScanServiceLoaded { get; private set; }

    public PlustecDocumentScanner() {
      InitializeScanner();
      //Application.Context.StartActivity(new Intent(Application.Context,typeof(ScanDemoActivity)));
    }

    private void RunOnUiThread(Func<object> p) {
      throw new NotImplementedException();
    }

    private void InitializeScanner() {
      InitialObjects();
      BindService();
    }

    private void InitialObjects() {
      // init objects ..
    }

    private void InitialProfiles() {
      // Init profiles ..
    }

    private bool BindService() {
      Context context = Application.Context;
      Intent intent = new Intent(context, typeof(IPlkScanService));
      this._scanServiceConnection = new ServiceConnection(this._scanCallBack, this._systemCallBack);
      bool serviceBoundSuccess = context.BindService(intent, this._scanServiceConnection, Bind.AutoCreate);
      context.StartActivity(intent);
      if (serviceBoundSuccess) {
        ServiceConnection service = (ServiceConnection)this._scanServiceConnection;
        this._plcScanService = service.PlcScanService;
        return true;
      }
      return false;
    }

    public void StartScan() {
      ..
    }
  }
}

这就是 ServiceConnection 的样子

namespace DemoApplication.Droid.Plustec {
 internal class ServiceConnection : IServiceConnection {
   public IPlkScanService PlcScanService { get; private set; }

   public IntPtr Handle { get; set; }

   private PlkSystemCallBack _plkSystemCallBack;
   private PlkScanCallBack _plkScanCallBack;

   public ServiceConnection(PlkScanCallBack plkScanCallBack, PlkSystemCallBack plkSystemCallBack) {
     this._plkScanCallBack = plkScanCallBack;
     this._plkSystemCallBack = plkSystemCallBack;
   }

   public void OnServiceConnected(ComponentName name, IBinder service) {
     this.PlcScanService = PlkScanServiceStub.AsInterface(service);
     try {
       this.PlcScanService.InitService(this._plkScanCallBack);
       this.PlcScanService.RegisterSystemCallBack(this._plkSystemCallBack);
       this.PlcScanService.MountScannerDevice();
     } catch (RemoteException e) {
       e.PrintStackTrace();
     }
   }

   public void OnServiceDisconnected(ComponentName name) {
     try {
       if (this.PlcScanService != null) {
         this.PlcScanService.UnmountScannerDevice();
         this.PlcScanService.UnregisterSystemCallBack(this._plkSystemCallBack);
         this.PlcScanService.UnregisterCallBack(this._plkScanCallBack);
         this.PlcScanService.UninitService();
       }
     } catch (RemoteException e) {
       e.PrintStackTrace();
     }

     this.PlcScanService = null;
     this._plkSystemCallBack = null;
     this._plkScanCallBack = null;
   }

   public void Dispose() {
     throw new NotImplementedException();
   }
 }
}

这是抛出的异常

05-19 12:41:56.028 E/mono( 5112): 
05-19 12:41:56.028 E/mono( 5112): Unhandled Exception:
05-19 12:41:56.028 E/mono( 5112): System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.InvalidCastException: Specified cast is not valid.
05-19 12:41:56.028 E/mono    ( 5112):   at Android.Content.ContextWrapper.BindService(Android.Content.Intent service, Android.Content.IServiceConnection conn, Android.Content.Bind flags) [0x0002c] in /Users/builder/data/lanes/4468/b16fb820/source/monodroid/src/Mono.Android/platforms/android-25/src/generated/Android.Content.ContextWrapper.cs:810 
05-19 12:41:56.028 E/mono( 5112):   at DemoApplication.Droid.Plustec.PlustecDocumentScanner.BindService() [0x0002f] in C:\git\devOps\Quickzone\QuickzoneForScanner\DemoApplication\DemoApplication\DemoApplication.Android\Plustec\PlustecDocumentScanner.cs:136 
05-19 12:41:56.028 E/mono( 5112):   at DemoApplication.Droid.Plustec.PlustecDocumentScanner.InitializeScanner() [0x00008] in C:\git\devOps\Quickzone\QuickzoneForScanner\DemoApplication\DemoApplication\DemoApplication.Android\Plustec\PlustecDocumentScanner.cs:60 
05-19 12:41:56.028 E/mono( 5112):   at DemoApplication.Droid.Plustec.PlustecDocumentScanner..ctor() [0x00008] in C:\git\devOps\Quickzone\QuickzoneForScanner\DemoApplication\DemoApplication\DemoApplication.Android\Plustec\PlustecDocumentScanner.cs:50 
05-19 12:41:56.028 E/mono( 5112):   at(wrapper managed-to-native) System.Reflection.MonoCMethod:InternalInvoke(System.Reflection.MonoCMethod, object, object[], System.Exception&)
05-19 12:41:56.028 E/mono( 5112):   at System.Reflection.MonoCMethod.InternalInvoke(System.Object obj, System.Object[] parameters) [0x00002] in /Users/builder/data/lanes/4468/f913a78a/source/mono/mcs/class/corlib/System.Reflection/MonoMethod.cs:661 
05-19 12:41:56.028 E/mono( 5112):    --- End of inner exception stack trace ---
05-19 12:41:56.038 E/mono-rt( 5112): [ERROR]
FATAL UNHANDLED EXCEPTION: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.InvalidCastException: Specified cast is not valid.
05-19 12:41:56.038 E/mono-rt ( 5112):   at Android.Content.ContextWrapper.BindService(Android.Content.Intent service, Android.Content.IServiceConnection conn, Android.Content.Bind flags) [0x0002c] in /Users/builder/data/lanes/4468/b16fb820/source/monodroid/src/Mono.Android/platforms/android-25/src/generated/Android.Content.ContextWrapper.cs:810 
05-19 12:41:56.038 E/mono-rt( 5112):   at DemoApplication.Droid.Plustec.PlustecDocumentScanner.BindService() [0x0002f] in C:\git\devOps\Quickzone\QuickzoneForScanner\DemoApplication\DemoApplication\DemoApplication.Android\Plustec\PlustecDocumentScanner.cs:136 
05-19 12:41:56.038 E/mono-rt( 5112):   at DemoApplication.Droid.Plustec.PlustecDocumentScanner.InitializeScanner() [0x00008] in C:\git\devOps\Quickzone\QuickzoneForScanner\DemoApplication\DemoApplication\DemoApplication.Android\Plustec\PlustecDocumentScanner.cs:60 
05-19 12:41:56.038 E/mono-rt( 5112):   at DemoApplication.Droid.Plustec.PlustecDocumentScanner..ctor() [0x00008] in C:\git\devOps\Quickzone\QuickzoneForScanner\DemoApplication\DemoApplication\DemoApplication.Android\Plustec\PlustecDocumentScanner.cs:50 
05-19 12:41:56.038 E/mono-rt( 5112):   at(wrapper managed-to-native) System.Reflection.MonoCMethod:InternalInvoke(System.Reflection.MonoCMethod, object, object[], System.Exception&)
05-19 12:41:56.038 E/mono-rt( 5112):   at System.Reflection.MonoCMethod.InternalInvoke(System.Object obj, System.Object[] parameters) [0x00002] in /Users/builder/data/lanes/4468/f913a78a/source/mono/mcs/class/corlib/System.Reflection/MonoMethod.cs:661 
05-19 12:41:56.038 E/mono-rt( 5112):    --- End of inner exception stack trace ---
InspectorDebugSession(7): HandleTargetEvent: TargetExited

调用时抛出异常

context.BindService(intent, this._scanServiceConnection, Bind.AutoCreate);

有人知道我做错了什么吗？

Answer 1

经过几个小时的搜索和调试，我终于找到了问题所在。
我的 ServiceConnection 必须扩展 Java.Lang.Object

 internal class ServiceConnection : Java.Lang.Object, IServiceConnection {
   public IPlkScanService PlcScanService { get; private set; }