android - 当按钮位于 fragment 中时将按钮绑定(bind)到 ViewModel 命令

Question

我使用的是内置在最新 Android 中的抽屉导航。

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:local="http://schemas.android.com/apk/res-auto"
    android:id="@+id/Home_HomeView_DrawerLayout" >
<!-- The main content view -->
    <FrameLayout
        android:id="@+id/Home_HomeView_ContentFrame" />
<!-- The navigation drawer -->

    <!-- ... -->

</android.support.v4.widget.DrawerLayout>

在我的 HomeView 中，我根据 Selected Item 设置了 Home_HomeView_ContentFrame fragment

private void SelectItem(int position)
{
    var fragment = new HomeFragment(ViewModel);
    var arguments = new Bundle();
    fragment.Arguments = arguments;
    _actionBarTitle = ((HomeViewModel)ViewModel).NavigationItems[position].Text;

    SupportFragmentManager.BeginTransaction()
                          .Replace(Resource.Id.Home_HomeView_ContentFrame, fragment)
                          .Commit();

    _topDrawerList.SetItemChecked(position, true);
    ActionBar.Title = _actionBarTitle;


    _navigationDrawer.CloseDrawer(_drawerInnerLayout);
}

HomeFragment 是为 MvvmCross 设置 BindingContext

public sealed class HomeFragment : MvxFragment
{

    public HomeFragment(IMvxViewModel viewModel)
    {
        ViewModel = viewModel;
    }

    public override View OnCreateView(LayoutInflater layoutInflater, ViewGroup viewGroup, Bundle bundle)
    {
        // A breakpoint below shows that the ViewModel does in fact contain the IPlayCommand as expected.
        BindingContext = new MvxAndroidBindingContext(Activity, new MvxSimpleLayoutInflater(layoutInflater), ViewModel);
        var rootView = layoutInflater.Inflate(Resource.Layout.Home_HomeFragment, viewGroup, false);

        Activity.Title = Resources.GetString(Resource.String.ApplicationName);
        return rootView;
    }
}

在 Home_HomeFragment 布局中，我有一个绑定(bind)到 IMvxCommand 的按钮。请注意，此按钮基于 @Stuart's example.

    <FutureState.AudioBook.Droid.Ui.Controls.FsmButton
        android:id="@+id/Home_HomeFragment_PlayPauseIcon"
        android:clickable="true"
        android:adjustViewBounds="true"
        local:MvxBind="Command PlayCommand; CommandParameter ." />

它绑定(bind)的 ViewModel 目前非常简单。

public class HomeViewModel : ViewModelBase
{
    public IList<NavigationItem> NavigationItems;

    public HomeViewModel(IPlayCommand playCommand)
    {
        // playCommand is being resolved by the IoC
        _playCommand = playCommand;
    }

    private IPlayCommand _playCommand;
    public IPlayCommand PlayCommand
    {
        get { return _playCommand; }
        set
        {
            _playCommand = value;
            RaisePropertyChanged(() => PlayCommand);
        }
    }
}

当我在 HomeFragment 的 BindingContext 行放置断点时，我绝对可以看到 ViewModel 填充了 PlayCommand。

我遇到的问题是触摸按钮的 Action 不会触发 PlayCommand。我哪里错了？

Answer 1

Android inflate 不知道 mvvmcross 绑定(bind)。

要使用基于 XML 的绑定(bind)，您必须使用 BindingInflate - 请参阅 http://mvvmcross.blogspot.com 中的示例代码在 https://github.com/MvvmCross/NPlus1DaysOfMvvmCross 中- 包括 n=26 中的 fragment - https://github.com/MvvmCross/NPlus1DaysOfMvvmCross/blob/master/N-26-Fraggle/Rock.Droid/Views/SubFrag.cs

http://motzcod.es/post/60427389481/effective-navigation-in-xamarin-android-part-1 中还有一个抽屉导航示例