MvvmCross

Question

我每次旋转设备时都会崩溃。我正在使用 MvvmCross 4.0.0.beta-3，这是我设置应用程序的方式：

Setup.cs

    protected override IMvxAndroidViewPresenter CreateViewPresenter()
    {
        var customPresenter = new MvxFragmentsPresenter();
        Mvx.RegisterSingleton<IMvxFragmentsPresenter>(customPresenter);
        return customPresenter;
    }

ShellPage.cs

    public abstract class ActivityBase<TViewModel> : MvxCachingFragmentCompatActivity<TViewModel>
                                                     where TViewModel : MvxViewModel
    {
        .
        .
        .
    }

HomePage.cs

    [Activity(
    Label = "Home",
    MainLauncher = true,
    LaunchMode = LaunchMode.SingleTop)]
    public class ShellPage : ActivityBase<ShellPageViewModel>, IMvxFragmentHost
    {
        .
        .
        .
        public void RegisterFragment<TFragment, TViewModel>(string tag, Bundle args)
            where TFragment : IMvxFragmentView
            where TViewModel : IMvxViewModel
        {
            var customPresenter = Mvx.Resolve<IMvxFragmentsPresenter>();
            customPresenter.RegisterViewModelAtHost<TViewModel>(this);
            RegisterFragment<TFragment, TViewModel>(tag);
        }

        public bool Show(MvxViewModelRequest request, Bundle bundle)
        {
            if (request.ViewModelType == typeof(MenuContentViewModel))
            {
                ShowFragment(request.ViewModelType.Name, Resource.Id.navigation_frame, bundle);
                return true;
            }
            else
            {
                ShowFragment(request.ViewModelType.Name, Resource.Id.content_frame, bundle, true);
                return true;
            }
        }
        .
        .
        .   
    }

MainFragment.cs

    [MvxOwnedViewModelFragment]
    [Register("xxxxx.android.fragments.MainFragment")]
    public class MainFragment : MvxFragment<MainFragmentViewModel>
    {
        .
        .
        .
    }

我发布了上面的代码以表明我正在使用 MvxCachingFragmentCompatActivity 作为基础 activity，IMvxFragmentHost 因为我的 ShellPage 是唯一使用 NavigationDrawer 交换片段 in/out 的页面，以及我的片段上的 [MvxOwnedViewModelFragment] 属性。

旋转时出现以下错误：

    10-20 12:10:02.470 I/MonoDroid( 6108): UNHANDLED EXCEPTION:
    10-20 12:10:02.471 I/MonoDroid( 6108): System.NullReferenceException: Object reference not set to an instance of an object
    10-20 12:10:02.471 I/MonoDroid( 6108): at Cirrious.MvvmCross.Droid.Support.AppCompat.MvxCachingFragmentCompatActivity.RestoreLookupFromSleep ()
    10-20 12:10:02.471 I/MonoDroid( 6108): at Cirrious.MvvmCross.Droid.Support.AppCompat.MvxCachingFragmentCompatActivity.OnPostCreate (Android.OS.Bundle)

有什么想法吗？

谢谢！

Answer 1

今天发布的新 MvvmCross beta4 对此进行了多项修复。样本也更新了很多：https://github.com/MvvmCross/MvvmCross-AndroidSupport/tree/master/Samples

MvvmCross - 设备旋转时崩溃

MvvmCross - Crash on device rotation

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