Xamarin OpenGL GLSurfaceView構造函數拋出空引用異常

Question

我想用Xamarin opengl實現android LiveWallpaper。 但是當我激活LiveWallpaper時，GLSurfaceView在構造函數中拋出空引用異常。

錯誤行： 調用GLSurfaceView的基礎構造函數時調用base（context）。

錯誤細節： 顯示java.lang.NullPointerException：嘗試上的空對象引用調用接口方法 '空隙android.view.SurfaceHolder.addCallback（android.view.SurfaceHolder $回調）'

[Service(Label = "@string/ApplicationName", Permission = "android.permission.BIND_WALLPAPER")] 
[IntentFilter(new[] { "android.service.wallpaper.WallpaperService" })] 
[MetaData("android.service.wallpaper", Resource = "@layout/MyLiveWallpaper")] 
public class OpenGLWallpaperService : WallpaperService 
{ 
    public override Engine OnCreateEngine() 
    { 
     return new OpenGLWallpaperEngine(this); 
    } 

    public class OpenGLWallpaperEngine : Engine 
    { 
     private readonly OpenGLWallpaperService _serviceInstance; 

     public OpenGLWallpaperView GLWallpaperView { get; set; } 

     public OpenGLWallpaperEngine(OpenGLWallpaperService serviceInstance) 
      : base(serviceInstance) 
     { 
      _serviceInstance = serviceInstance; 
     } 

     public override void OnCreate(ISurfaceHolder surfaceHolder) 
     { 
      base.OnCreate(surfaceHolder); 
      GLWallpaperView = new OpenGLWallpaperView(this, _serviceInstance, surfaceHolder); 
     } 
    } 
} 

public class OpenGLWallpaperView : GLSurfaceView 
{ 
    private readonly OpenGLWallpaperService.OpenGLWallpaperEngine _engineInstance; 

    public override ISurfaceHolder Holder { get; } 

    public OpenGLWallpaperView(OpenGLWallpaperService.OpenGLWallpaperEngine engineInstance, 
     Context context, ISurfaceHolder surfaceHolder) 
     : base(context) 
    { 
     _engineInstance = engineInstance; 
     Holder = surfaceHolder; 
    } 
} 

Answer 1

我在做錯誤的重寫持有人。持有人不應被覆蓋。

取消以下行和相關事項：
public override ISurfaceHolder Holder {get; }