来自 command/viewmodel 的 WPF DataGridView 键盘焦点

Question

网上满是类似的问题，我也搜索了SO（最接近的：[1]、[2]、[3]）。

到目前为止，我无法相信这个问题是ugly/non-trivial。

我有一个 DataGridView。我还有其他控件（在本例中：在 DataGridView 的列 headers 中）。我想支持快速 'jump to grid' 命令。此命令需要将键盘焦点设置到网格，以便用户可以使用箭头键在行之间导航。

在下面的家中一起玩的简单测试用例。 select 数据网格中的元素非常容易，但似乎没有办法为其提供键盘焦点。除了在 code-behind 操作中，即使那样你似乎也必须跳过箍（参见 [2]，杂耍让单元格容器设置键盘焦点，因为 .. grid 和 row 似乎不起作用据我所知）。

好像很简单？

一些琐碎的模型：

public class Item
{
    public int DayOfMonth { get; set; }
    public string Weekday { get; set; }
}

匹配简单的视图模型（假设您有一个 RelayCommand 实现，请参阅 JumpToGrid 以获得 ~meat~）：

public class MainViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private IList<Item> m_items;
    public IList<Item> SampleItems
    {
        get { return m_items; }
        set { SetField(ref m_items, value, () => SampleItems); }
    }

    private Item m_currentItem;
    public Item CurrentItem
    {
        get { return m_currentItem; }
        set { SetField(ref m_currentItem, value, () => CurrentItem); }
    }

    public ICommand JumpToGridCommand { get; private set; }

    public MainViewModel()
    {
        JumpToGridCommand = new RelayCommand(p => JumpToGrid());

        var items = new List<Item>();
        var today = DateTime.Now;
        for (int i = 1; i <= DateTime.DaysInMonth(today.Year, today.Month); i++ )
        {
            items.Add(new Item { DayOfMonth = i, Weekday = new DateTime(today.Year, today.Month, i).DayOfWeek.ToString() });
        }
        SampleItems = items;
    }

    private void JumpToGrid()
    {
        // I can change the selection just fine
        CurrentItem = SampleItems[0];

        // But the keyboard focus is broken, up/down doesn't work as expected
    }

    protected bool SetField<T>(ref T field, T value, Expression<Func<T>> selectorExpression)
    {
        if (selectorExpression == null) throw new ArgumentNullException("selectorExpression");
        MemberExpression body = selectorExpression.Body as MemberExpression;
        if (body == null) throw new ArgumentException("The body must be a member expression");
        var fieldName = body.Member.Name;

        if (EqualityComparer<T>.Default.Equals(field, value)) return false;
        field = value;
        OnPropertyChanged(fieldName);
        return true;
    }

    protected void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

简单视图（code-behind 是空的，除了加载事件中的 "DataContext = new MainViewModel()" 之外： <Window x:Class="DataGridKeyboardFocus.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:DataGridKeyboardFocus" Loaded="Window_Loaded" Title="MainWindow" Height="350" Width="525"> <Grid> <DataGrid ColumnWidth="*" AutoGenerateColumns="False" Margin="1" ItemsSource="{Binding SampleItems}" SelectedItem="{Binding CurrentItem, Mode=TwoWay}" SelectionUnit="FullRow" IsReadOnly="True"> <DataGrid.Columns> <DataGridTextColumn Binding="{Binding DayOfMonth}"> <DataGridTextColumn.HeaderTemplate> <DataTemplate> <StackPanel Orientation="Vertical"> <TextBlock Text="Some label" /> <TextBox> <TextBox.InputBindings> <KeyBinding Modifiers="Control" Key="Tab" Command="{Binding DataContext.JumpToGridCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:MainWindow}}}" /> </TextBox.InputBindings> </TextBox> </StackPanel> </DataTemplate> </DataGridTextColumn.HeaderTemplate> </DataGridTextColumn> <DataGridTextColumn Binding="{Binding Weekday}"> <DataGridTextColumn.HeaderTemplate> <DataTemplate> <StackPanel Orientation="Vertical"> <TextBlock Text="Another label" /> <TextBox> <TextBox.InputBindings> <KeyBinding Modifiers="Control" Key="Tab" Command="{Binding DataContext.JumpToGridCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:MainWindow}}}" /> </TextBox.InputBindings> </TextBox> </StackPanel> </DataTemplate> </DataGridTextColumn.HeaderTemplate> </DataGridTextColumn> </DataGrid.Columns> </DataGrid> </Grid> </Window>

1: Keyboard focus vs logical focus in WPF

2: Keyboard focus to DataGrid

3: WPF: Can't control keyboard focus

Answer 1

我已经为网格添加了 selection changed 事件并试图 select 一个单元格。参考下面的代码。

 <DataGrid
            ColumnWidth="*" 
            AutoGenerateColumns="False"
            Margin="1"
            ItemsSource="{Binding SampleItems}" 
            SelectedItem="{Binding CurrentItem, Mode=TwoWay}"
            SelectionUnit="FullRow"
            IsReadOnly="True"
        SelectionChanged="DataGrid_SelectionChanged">
        <DataGrid.Columns>
            <DataGridTextColumn Binding="{Binding DayOfMonth}">
                <DataGridTextColumn.HeaderTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Vertical">
                            <TextBlock Text="Some label" />
                            <TextBox>
                                <TextBox.InputBindings>
                                    <KeyBinding Modifiers="Control" Key="T" Command="{Binding DataContext.JumpToGridCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" />
                                </TextBox.InputBindings>
                            </TextBox>
                        </StackPanel>
                    </DataTemplate>
                </DataGridTextColumn.HeaderTemplate>
            </DataGridTextColumn>
            <DataGridTextColumn Binding="{Binding Weekday}">
                <DataGridTextColumn.HeaderTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Vertical">
                            <TextBlock Text="Another label" />
                            <TextBox>
                                <TextBox.InputBindings>
                                    <KeyBinding Modifiers="Control" Key="T" Command="{Binding DataContext.JumpToGridCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" />
                                </TextBox.InputBindings>
                            </TextBox>
                        </StackPanel>
                    </DataTemplate>
                </DataGridTextColumn.HeaderTemplate>
            </DataGridTextColumn>
        </DataGrid.Columns>
    </DataGrid>

代码隐藏。

private void DataGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        DataGrid dg = sender as DataGrid;
        SelectRowByIndex(dg, dg.SelectedIndex);
    }
    public static DataGridCell GetCell(DataGrid dataGrid, DataGridRow rowContainer, int column)
    {
        if (rowContainer != null)
        {
            DataGridCellsPresenter presenter = FindVisualChild<DataGridCellsPresenter>(rowContainer);
            if (presenter == null)
            {
                /* if the row has been virtualized away, call its ApplyTemplate() method
                 * to build its visual tree in order for the DataGridCellsPresenter
                 * and the DataGridCells to be created */
                rowContainer.ApplyTemplate();
                presenter = FindVisualChild<DataGridCellsPresenter>(rowContainer);
            }
            if (presenter != null)
            {
                DataGridCell cell = presenter.ItemContainerGenerator.ContainerFromIndex(column) as DataGridCell;
                if (cell == null)
                {
                    /* bring the column into view
                     * in case it has been virtualized away */
                    dataGrid.ScrollIntoView(rowContainer, dataGrid.Columns[column]);
                    cell = presenter.ItemContainerGenerator.ContainerFromIndex(column) as DataGridCell;
                }
                return cell;
            }
        }
        return null;
    }
    public static T FindVisualChild<T>(DependencyObject obj) where T : DependencyObject
    {
        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
        {
            DependencyObject child = VisualTreeHelper.GetChild(obj, i);
            if (child != null && child is T)
                return (T)child;
            else
            {
                T childOfChild = FindVisualChild<T>(child);
                if (childOfChild != null)
                    return childOfChild;
            }
        }
        return null;
    }
    public static void SelectRowByIndex(DataGrid dataGrid, int rowIndex)
    {
        DataGridRow row = dataGrid.ItemContainerGenerator.ContainerFromIndex(rowIndex) as DataGridRow;
        if (row != null)
        {
            DataGridCell cell = GetCell(dataGrid, row, 0);
            if (cell != null)
                cell.Focus();
        }
    }

参考link。 http://social.technet.microsoft.com/wiki/contents/articles/21202.wpf-programmatically-selecting-and-focusing-a-row-or-cell-in-a-datagrid.aspx