在Windows App Store Gridview中迭代所选项目

Question

我知道这很长,但请耐心等待.

我使用MVVM光框架在MVVM光样本中创建了一个非常类似于Laurent Bugnion的"MyFriends"程序的Windows应用商店程序.

在他的程序中,他使用gridview的SelectedItem属性来跟踪哪个项目是所选项目.

问题是,我让用户能够在GridView上选择多个项目,然后使用App Bar上的按钮对它们进行操作.对于此SelectedItem将无法正常工作.

有谁知道如何使用多选GridView进行此工作？我已经根据WPF上的一些文章尝试了GridViewItem的IsSelected属性,但这似乎不起作用.SelectedTimesheets getter在调用时总是返回空.这是我到目前为止:

MainPage.xaml(绑定到带有子TimesheetViewModel可观察集合的MainViewModel):

<GridView 
    x:Name="itemGridView"
    IsItemClickEnabled="True"
    ItemsSource="{Binding Timesheets}"
    ItemTemplate="{StaticResource TimesheetTemplate}" 
    Margin="10"
    Grid.Column="0"
    SelectionMode="Multiple"
    helpers:ItemClickCommand.Command="{Binding NavigateTimesheetCommand}" RenderTransformOrigin="0.738,0.55"  >
    <GridView.ItemContainerStyle>
        <Style TargetType="GridViewItem">
            <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
        </Style>
    </GridView.ItemContainerStyle>

</GridView>

MainViewModel(从完整代码中删除):

public class MainViewModel : ViewModelBase
{
    private readonly IDataService _dataService;
    private readonly INavigationService _navigationService;

    /// <summary>
    /// Initializes a new instance of the MainViewModel class.
    /// </summary>
    public MainViewModel(IDataService dataService, INavigationService navigationService)
    {
        _dataService = dataService;
        _navigationService = navigationService;

        Timesheets = new ObservableCollection<TimesheetViewModel>();
        ExecuteRefreshCommand();

    }

    public ObservableCollection<TimesheetViewModel> Timesheets
    {
        get;
        private set;
    }

    public IEnumerable<TimesheetViewModel> SelectedTimesheets
    {
        get { return Timesheets.Where(o => o.IsSelected); }
    }

    private async void ExecuteRefreshCommand()
    {
        var timesheets = await _dataService.GetTimesheets("domain\\user");

        if (timesheets != null)
        {
            Timesheets.Clear();

            foreach (var timesheet in timesheets)
            {
                Timesheets.Add(new TimesheetViewModel(timesheet));
            }

        }
    }
}

TimesheetViewModel:

public class TimesheetViewModel: ViewModelBase
{

    public bool IsSelected { get; set; }

    public Timesheet Model
    {
        get;
        private set;
    }

    public TimesheetViewModel(Timesheet model)
    {
        Model = model;

    }
}

如果我手动设置IsSelected属性,则SelectedTimesheets lambda可以工作,因此问题出在XAML与IsSelected属性绑定的某处.

任何帮助,将不胜感激.

Answer 1

当然,我知道你的意思.太糟糕了,这不是自动化,但事实并非如此.该解决方案涉及一个GridView继承自的简单自定义GridView.没有什么太疯狂的,也就是说,如果你让它沉入其中.这是代码,我只是测试它:

这是你的XAML:

<Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
    <Grid.ColumnDefinitions >
        <ColumnDefinition />
        <ColumnDefinition />
    </Grid.ColumnDefinitions>
    <local:MyGridView ItemsSource="{Binding Items}" SelectionMode="Multiple"
                      BindableSelectedItems="{Binding Selected}" />
    <local:MyGridView Grid.Column="1" ItemsSource="{Binding Selected}" />
</Grid>

这是您的视图模型(超简化):

public class ViewModel
{
    ObservableCollection<string> m_Items
        = new ObservableCollection<string>(Enumerable.Range(1, 100).Select(x => x.ToString()));
    public ObservableCollection<string> Items { get { return m_Items; } }

    ObservableCollection<object> m_Selected = new ObservableCollection<object>();
    public ObservableCollection<object> Selected { get { return m_Selected; } }
}

这是你的自定义gridview:

public class MyGridView : GridView
{
    public ObservableCollection<object> BindableSelectedItems
    {
        get { return GetValue(BindableSelectedItemsProperty) as ObservableCollection<object>; }
        set { SetValue(BindableSelectedItemsProperty, value as ObservableCollection<object>); }
    }
    public static readonly DependencyProperty BindableSelectedItemsProperty =
        DependencyProperty.Register("BindableSelectedItems",
        typeof(ObservableCollection<object>), typeof(MyGridView),
        new PropertyMetadata(null, (s, e) =>
        {
            (s as MyGridView).SelectionChanged -= (s as MyGridView).MyGridView_SelectionChanged;
            (s as MyGridView).SelectionChanged += (s as MyGridView).MyGridView_SelectionChanged;
        }));
    void MyGridView_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if (BindableSelectedItems == null)
            return;
        foreach (var item in BindableSelectedItems.Where(x => !this.SelectedItems.Contains(x)).ToArray())
            BindableSelectedItems.Remove(item);
        foreach (var item in this.SelectedItems.Where(x => !BindableSelectedItems.Contains(x)))
            BindableSelectedItems.Add(item);
    }
}

只是一个新的财产BindableSelectedItems.

祝你好运!