Question

我目前正在开发一个带有Xamarin.Android和MvvmCross的移动应用程序。我有不同的视图正常工作（MvxActivity）。但是我对上一个观点有疑问：

当我使用ShowViewModel <MvxViewModel>导航到它时，应用程序崩溃而没有信息（是的，堆栈跟踪仍为空）。在此视图中，我尝试使用CoordinatorLayout创建材质选项卡。为此，我有一个ViewModel（在Windows中正常工作）：

public class HomeViewModel : MvxViewModel
{
    protected readonly IService _service;

    protected const string ValidateEditionMessage = "Voulez-vous modifier?";
    protected const string Edit = "Modifier";
    protected const string Confirmation = "Confirmation";
    protected const string Cancel = "Annuler";

    public IMvxCommand SaveChangedCommand
    {
        get
        {
            return new MvxCommand<Item>(async (m) =>
            {
                var result = await Mvx.Resolve<IDialogService>().ShowAsync(ValidateEditionMessage, Confirmation, Edit, Cancel);
                if (result.Value) await _service.UpdateAsync(_item.Id, _item);
            });
        }
    }

    protected Item _item;
    public Item Item
    {
        get { return _item; }
        set { this.RaiseAndSetIfChanged(ref _item, value, () => Item); }
    }

    private FirstViewModel _FirstViewModel;
    public FirstViewModel FirstViewModel
    {
        get { return _FirstViewModel; }
        set { this.RaiseAndSetIfChanged(ref _FirstViewModel, value, () => FirstViewModel); }
    }

    private SecondViewModel _SecondViewModel;
    public SecondViewModel SecondViewModel
    {
        get { return _SecondViewModel; }
        set { this.RaiseAndSetIfChanged(ref _SecondViewModel, value, () => SecondViewModel); }
    }

    private ThirdViewModel _ThirdViewModel;
    public ThirdViewModel ThirdViewModel
    {
        get { return _ThirdViewModel; }
        set { this.RaiseAndSetIfChanged(ref _ThirdViewModel, value, () => ThirdViewModel); }
    }

    public HomeViewModel(IService service)
    {
        _service = service;
        FirstViewModel = new FirstViewModel();
        SecondViewModel = new SecondViewModel();
        ThirdViewModel = new ThirdViewModel();
    }

    public async void Init(int id)
    {
        Item = await _service.GetItemAsync(id);
        FirstViewModel.Item = SecondViewModel.Item = ThirdViewModel.Item = Item;
    }
}

此ViewModel的Android视图：

[Activity(Theme = "@style/Theme.AppCompat")]
public class HomeView : MvxCachingFragmentCompatActivity<HomeViewModel>
{
    protected override void OnCreate(Bundle bundle)
    {
        Mvx.Trace("HomeView OnCreate(bundle)");
        base.OnCreate(bundle);
        SetContentView(Resource.Layout.Home);
        var viewPager = FindViewById<ViewPager>(Resource.Id.viewpager);
        if (viewPager != null)
        {
            Mvx.Trace("viewPager found in " + nameof(HomeView));
            var fragments = new List<MvxCachingFragmentStatePagerAdapter.FragmentInfo>
            {
                new MvxCachingFragmentStatePagerAdapter.FragmentInfo("First", typeof(FirstFragment), ViewModel.FirstViewModel),
                new MvxCachingFragmentStatePagerAdapter.FragmentInfo("Second", typeof(SecondFragment), ViewModel.SecondViewModel),
                new MvxCachingFragmentStatePagerAdapter.FragmentInfo("Third", typeof(ThirdFragment), ViewModel.ThirdViewModel)
            };
            Mvx.Trace("{0} fragments", fragments.Count);

            viewPager.Adapter = new MvxCachingFragmentStatePagerAdapter(this, SupportFragmentManager, fragments);
        }
        var tabLayout = FindViewById<TabLayout>(Resource.Id.tabs);
        tabLayout.SetupWithViewPager(viewPager);
    }
}

此视图的AXML布局（Resource.Layout.Home）：

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/main_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
            app:layout_scrollFlags="scroll|enterAlways" />
        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:paddingLeft="16dp"
            app:tabGravity="center"
            app:tabMode="scrollable" />
    </android.support.design.widget.AppBarLayout>
    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="fill_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />
</android.support.design.widget.CoordinatorLayout>

显然，我有三个片段：FirstFragment，SecondFragment，ThirdFragment，看起来像这样：

public class FirstFragment : MvxFragment
{
    public FirstFragment()
    {
        Mvx.Trace(nameof(FirstFragment) + " constructor");
    }

    public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        return this.BindingInflate(Resource.Layout.First, null);
    }
}

The corresponding ViewModels are basic, run on Windows, and are available on my GitHub, here

我的stacktrace的最后一行：

mvx : Diagnostic :  17.66 Showing ViewModel HomeViewModel
[art] JNI RegisterNativeMethods: attempt to register 0 native methods for md5204979768ea66d3a79201c4efd7c602a.MvxAppCompatActivity_1
mvx : Diagnostic :  17.69 HomeView constructor
[Mono] Assembly Ref addref MyApp.Droid[0xac176060] -> Xamarin.Android.Support.Design[0xac177b00]: 2
[Mono] Assembly Ref addref Xamarin.Android.Support.Design[0xac177b00] -> Xamarin.Android.Support.v4[0xac178640]: 5
mvx : Diagnostic :  17.70 HomeView OnCreate(bundle)
[Mono] Assembly Ref addref MvvmCross.Droid.Support.V7.AppCompat[0xac1787c0] -> Xamarin.Android.Support.v4[0xac178640]: 6
mvx : Diagnostic :  17.71 Attempting to load new ViewModel from Intent with Extras
[Mono] Assembly Ref addref MvvmCross.Droid.Support.V7.AppCompat[0xac1787c0] -> Xamarin.Android.Support.v4[0xac178640]: 6
mvx : Diagnostic :  17.71 Attempting to load new ViewModel from Intent with Extras
[Mono] Assembly Ref addref MvvmCross.Droid.Support.V7.AppCompat[0xac1787c0] -> System[0xac253020]: 13
[art] Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
[Mono] [0x97cba930] worker finishing
[] suspend_thread suspend took 201 ms, which is more than the allowed 200 ms
[libc] Fatal signal 6 (SIGABRT), code -6 in tid 6991 (Threadpool work)

Answer 1

由于存储库为空。

一个原因可能是您没有正确注册元素：

[MvxFragment(typeof(MainActivityViewModel), Resource.Id.fragmentone)]
[Register("mobilexcp.xcpandroidapp.fragments.fragmentone")]
public class FragmentOne: BaseFragment<FirstViewModel>

不确定您是否在Setup.cs中有此内容

    /// <summary>
    /// This is very important to override. The default view presenter does not know how to show fragments!
    /// </summary>
    protected override IMvxAndroidViewPresenter CreateViewPresenter()
    {

        var mvxFragmentsPresenter = new MvxFragmentsPresenter(AndroidViewAssemblies);
        Mvx.RegisterSingleton<IMvxAndroidViewPresenter>(mvxFragmentsPresenter);
        return mvxFragmentsPresenter;
    }

我对片段的主要活动是MvxCachingFragmentCompatActivity。

MvvmCross：Android应用程序在没有信息的情况下崩溃

1 个答案: