Xamarin-MediaRouteButton ShowDialog()方法抛出NullPointerException(Xamarin.Android.Support.v7.MediaRouter)

我正在尝试在Xamarin Android中实现一个MediaRouteButton,以在该地区找到ChromeCast设备,该设备使用Android支持库(NuGeT包) 我下载了一个示例应用程序(它可以正常工作,下载GooglePlayServices-Cast组件时提供的CastingCall项目示例),但当我试图在上面传输代码时,它在单击以下按钮时抛出一个错误:

[AndroidRuntime] java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
[AndroidRuntime]    at android.support.v7.app.MediaRouteChooserDialog.onCreate(MediaRouteChooserDialog.java:167)
[AndroidRuntime]    at android.app.Dialog.dispatchOnCreate(Dialog.java:465)
[AndroidRuntime]    at android.app.Dialog.show(Dialog.java:288)
[AndroidRuntime]    at android.support.v4.app.DialogFragment.onStart(DialogFragment.java:406)
[AndroidRuntime]    at android.support.v4.app.Fragment.performStart(Fragment.java:1986)
[AndroidRuntime]    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1102)
[AndroidRuntime]    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1248)
[AndroidRuntime]    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
[AndroidRuntime]    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1613)
[AndroidRuntime]    at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:517)
[AndroidRuntime]    at android.os.Handler.handleCallback(Handler.java:739)
[AndroidRuntime]    at android.os.Handler.dispatchMessage(Handler.java:95)
[AndroidRuntime]    at android.os.Looper.loop(Looper.java:145)
[AndroidRuntime]    at android.app.ActivityThread.main(ActivityThread.java:6117)
[AndroidRuntime]    at java.lang.reflect.Method.invoke(Native Method)
[AndroidRuntime]    at java.lang.reflect.Method.invoke(Method.java:372)
[AndroidRuntime]    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
[AndroidRuntime]    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)

mediaRouteButton = FindViewById<Android.Support.V7.App.MediaRouteButton> (Resource.Id.mediaRouteButton);
mediaRouter = MediaRouter.GetInstance (this);
mediaRouteSelector = new MediaRouteSelector.Builder ()
            .AddControlCategory (MediaControlIntent.CategoryRemotePlayback)
            .Build();
mediaRouteButton.RouteSelector = mediaRouteSelector;

MediaRouteButton未灰显,这意味着它正在检测该区域中的正确路由(我调试它只是为了确保,并且mediaRouter对象包含示例应用程序中显示的相同路由),但在尝试创建允许用户选择路由的对话框(mediaRouter.ShowDialog())时,它似乎崩溃了。我找不到这个错误的修复程序,因为我无法访问这个类的源代码,因为它似乎正在崩溃(MediaRouteChooserDialog)。我甚至尝试实现一个自定义对话框工厂( https://developer.android.com/reference/android/support/v7/app/MediaRouteDialogFactory.html

有什么想法吗?