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如何使用MvvmCross 6.x在TabLayout中正确使用片段

android-tablayout mvvmcross xamarin android c#

Vinícius Queiroz Usman Kurd · 技术社区 · 7 年前

问题

但我收到一个异常,然后在运行时崩溃,此时应该显示此活动:

演示者词典

代码

这就是我的代码的样子,我是按照 Playground example 以及 Documentation :

AppStart.cs:

public class AppStart : MvxAppStart
{
    private readonly IMvxNavigationService _mvxNavigationService;

    public AppStart(IMvxApplication app, IMvxNavigationService mvxNavigationService)
        : base(app, mvxNavigationService)
    {
        _mvxNavigationService = mvxNavigationService;
    }

    protected override void NavigateToFirstViewModel(object hint = null)
    {
        Mvx.Resolve<IMvxNavigationService>().Navigate<TabLayoutViewModel>();
    }
}

TabLayoutViewModel.cs表格

public class TabLayoutViewModel: MvxViewModel
{
    public override async Task Initialize()
    {
        await base.Initialize();

        var tasks = new List<Task>();
        tasks.Add(Mvx.Resolve<IMvxNavigationService>().Navigate<FragmentTab1ViewModel>());
        tasks.Add(Mvx.Resolve<IMvxNavigationService>().Navigate<FragmentTab2ViewModel>());
        await Task.WhenAll(tasks);
    }
}

片段tab1viewmodel.cs (与FragmentTab2ViewModel.cs类似)

public class FragmentTab1ViewModel : MvxViewModel
{
    public override Task Initialize()
    {
        return base.Initialize();
    }
}

TabLayoutViewController.cs表格

[MvxActivityPresentation]
[Activity(Label = "", ScreenOrientation = ScreenOrientation.Portrait, LaunchMode = LaunchMode.SingleTask, Theme = "@style/LoginTheme")]
public class TabLayoutViewController: MvxAppCompatActivity<TabLayoutViewModel>
{
    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        SetContentView(Resource.Layout.TabLayoutView);

        var set = this.CreateBindingSet<TabLayoutViewController, TabLayoutViewModel>();

        set.Apply();
    }
}

TabLayoutView.axml

<?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:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:alwaysDrawnWithCache="false"
    android:background="#f4f4f4"
    android:minWidth="25px"
    android:minHeight="25px">
  <android.support.design.widget.TabLayout
      android:id="@+id/tabsTeste"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:paddingLeft="16dp"
      app:tabGravity="center"
      app:tabMode="scrollable" />
  <android.support.v4.view.ViewPager
      android:id="@+id/viewpagerTeste"
      android:layout_width="match_parent"
      android:layout_height="match_parent" />
</android.support.design.widget.CoordinatorLayout>

FragmentTab1ViewController.cs

[MvxTabLayoutPresentation(ActivityHostViewModelType = typeof(TabLayoutViewModel), ViewPagerResourceId = Resource.Id.viewpagerTest, TabLayoutResourceId = Resource.Id.tabsTest, Title = "Tab A")]
[Register("smartSolution.coleta.droid.view.FragmentTab1ViewController")]
public class FragmentTab1ViewController : MvxFragment<FragmentTab1ViewModel>
{
    public override Android.Views.View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        base.OnCreateView(inflater, container, savedInstanceState);

        var view = this.BindingInflate(Resource.Layout.FragmentTab1View, null);

        inflater.Inflate(Resource.Layout.FragmentTab1View, container, true);

        var set = this.CreateBindingSet<FragmentTab1ViewController, FragmentTab1ViewModel>();

        set.Apply();

        return view;
    }
}

(FragmentTab1View.axml和FragmentTab2View.axml只是带有文本视图的线性布局)

引发异常的原因是什么?
这是实现带有片段的TabLayout的推荐方法吗?
遵循mvvmcross6.x良好实践,可以做些什么来解决这个问题?

1 回复 | 直到 7 年前

fmaccaroni 7 年前

抛出该异常是因为该属性未在 AttributeTypesToActionsDictionary 的 Presenter .

在代码中,您可以在方法中看到这一点 RegisterAttributeTypes MvxAppCompatViewPresenter . 此外,在 docs AppCompat .

假设您得到了这个异常,我可以假设正在使用非AppCompat演示者,因此您正在使用 MvxAndroidSetup

要解决此问题,请确保使用 应用程序兼容性 类,特别是继承自 MvxAppCompatSetup where 这个已设置。还要确保您正在使用 MvxAppCompatApplication 所以如果 forces 你可以用的版本 Setup .

更新关于例外情况的评论 MvvmCross.Exceptions.MvxException: ViewPager not found

我认为问题是您正在导航到 Initialize

Playground Viewmodel 您应该有一个调用方法的命令来在ViewModel上执行导航:

...
ShowInitialViewModelsCommand = new MvxAsyncCommand(ShowInitialViewModels);
...

public IMvxAsyncCommand ShowInitialViewModelsCommand { get; private set; }

...

private async Task ShowInitialViewModels()
{
    var tasks = new List<Task>();
    tasks.Add(Mvx.Resolve<IMvxNavigationService>().Navigate<FragmentTab1ViewModel>());
    tasks.Add(Mvx.Resolve<IMvxNavigationService>().Navigate<FragmentTab2ViewModel>());
    await Task.WhenAll(tasks);
}

就像在 Playground View 你应该在你的电脑里调用命令 TabLayoutViewController :

protected override void OnCreate(Bundle bundle)
{
    base.OnCreate(bundle);

    SetContentView(Resource.Layout.TabLayoutView);

    var set = this.CreateBindingSet<TabLayoutViewController, TabLayoutViewModel>();

    set.Apply();

    if (bundle == null)
    {
        ViewModel.ShowInitialViewModelsCommand.Execute();
    }
}

嗨