c# - 删除 DataGrid 中自动生成的行

Question

我有一个数据网格。它绑定(bind)到名为 People 的 Person 集合。

允许用户添加新行，我的意思是 CanUserAddRows = true。

Enter 键在我的 DataGrid 中用作 TAB 键。

我的 DataGrid 中有三列，即:FirstName、LastName、City。名字是必需的。另外两个不是强制性的。

当用户在最后一行(自动生成的行)的第一个单元格上点击 Enter 时，如果该单元格为空，则计算机会猜测用户不想向 DataGrid 添加更多数据，并且焦点移动到 DataGrid 外部的按钮。

到目前为止一切正常。

问题:

通过在最后一行的第一个单元格上按 Enter 并将其保持为空，DataGrid 外部的按钮将获得焦点。那时我不希望用户看到 DataGrid 中的最后一个空行。

我尝试过的:

我尝试了两个事件:1. GotFocus 和 2. LostFocus

在 DataGrid 的 GotFocus 事件中，我设置了 CanUserAddRows = true在 DataGrid 的 LostFocus 事件中，我设置了 CanUserAddRows = false

但不幸的是，当 DataGrid 单元格内的 textBlock 获得焦点时，这不起作用，DataGrid 认为它已经失去了焦点。因此，CanUserAddRows 设置为 false，我收到错误消息。

我的代码:

人.cs

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string City { get; set; }
}

MainWindowViewModel.cs

public class MainWindowViewModel : INotifyPropertyChanged
{
    public MainWindowViewModel()
    {
        People = new ObservableCollection<Person>();
    }

    private ObservableCollection<Person> _people;
    public ObservableCollection<Person> People
    {
        get
        {
            return _people;
        }
        set
        {
            _people = value;
            OnPropertyChanged("People");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

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

主窗口.xaml

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="350" Width="525">

    <Window.DataContext>
        <local:MainWindowViewModel />
    </Window.DataContext>

    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="65*"/>
            <ColumnDefinition Width="9*"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="93*"/>
            <RowDefinition Height="14*"/>
        </Grid.RowDefinitions>
        <DataGrid x:Name="maindg" AutoGenerateColumns="True" ItemsSource="{Binding People}" Margin="0,0,0.4,-0.2" Grid.RowSpan="2" Grid.ColumnSpan="2" 
                  PreviewKeyDown="DataGrid_KeyDown_1" SelectedIndex="0" GridLinesVisibility="Vertical" 
                  SelectionMode="Single" SelectionUnit="CellOrRowHeader" >
        </DataGrid>

        <Button Height="20" Width="50" Content="Save" Margin="2.8,9.8,10.4,11.8" Grid.Column="1" Grid.Row="1" x:Name="btnSave" />
    </Grid>
</Window>

主窗口.xaml.cs

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private int FindRowIndex(DataGridRow row)
    {
        DataGrid dataGrid =
            ItemsControl.ItemsControlFromItemContainer(row)
            as DataGrid;

        int index = dataGrid.ItemContainerGenerator.
            IndexFromContainer(row);

        return index;
    }

    private object ExtractBoundValue(DataGridRow row,
                             DataGridCell cell)
    {
        // find the column that this cell belongs to
        DataGridBoundColumn col =
           cell.Column as DataGridBoundColumn;

        // find the property that this column is bound to
        Binding binding = col.Binding as Binding;
        string boundPropertyName = binding.Path.Path;

        // find the object that is related to this row
        object data = row.Item;

        // extract the property value
        PropertyDescriptorCollection properties =
            TypeDescriptor.GetProperties(data);

        PropertyDescriptor property = properties[boundPropertyName];
        if (property != null)
        {
            object value = property.GetValue(data);

            return value;
        }

        return null;
    }

    private void DataGrid_KeyDown_1(object sender, KeyEventArgs e)
    {
        if (e.Key != Key.Enter) return;

        DependencyObject dep = (DependencyObject)e.OriginalSource;
        //here we just find the cell got focused ...
        //then we can use the cell key down or key up
        // iteratively traverse the visual tree
        while ((dep != null) && !(dep is DataGridCell) && !(dep is DataGridColumnHeader))
        {
            dep = VisualTreeHelper.GetParent(dep);
        }

        if (dep == null)
            return;

        if (dep is DataGridCell)
        {
            try
            {
                //cancel if datagrid in edit mode
                maindg.CommitEdit();


                //Check if selected cell is on first column and last row
                if (maindg.CurrentColumn.DisplayIndex == 0)
                {
                    DependencyObject dep1 = dep;
                    while ((dep1 != null) && !(dep1 is DataGridRow))
                    {
                        dep1 = VisualTreeHelper.GetParent(dep1);
                    }

                    DataGridRow row = dep1 as DataGridRow;

                    if (FindRowIndex(row) == maindg.Items.Count - 1)
                    {
                        if (ExtractBoundValue(row, dep as DataGridCell) == null)
                        {
                            btnSave.Focus();
                            return;
                        }
                    }
                }
            }
            catch
            {
                maindg.CancelEdit();
            }
            //get current cell
            DataGridCell cell = dep as DataGridCell;
            //deselect current cell
            cell.IsSelected = false;
            //find next right cell
            var nextCell = cell.PredictFocus(FocusNavigationDirection.Right);
            //if next right cell null go for find next ro first cell
            if (nextCell == null)
            {
                DependencyObject nextRowCell;
                nextRowCell = cell.PredictFocus(FocusNavigationDirection.Down);
                //if next row is null so we have no more row Return;
                if (nextRowCell == null)
                {
                    nextRowCell = dep;
                    while ((nextRowCell as DataGridCell).PredictFocus(FocusNavigationDirection.Left) != null)
                        nextRowCell = (nextRowCell as DataGridCell).PredictFocus(FocusNavigationDirection.Left);
                    //change current cell
                    maindg.CurrentCell = new DataGridCellInfo(nextRowCell as DataGridCell);
                    //change selected cell
                    (nextRowCell as DataGridCell).IsSelected = true;
                    return;
                }
                //we do this because we cant use FocusNavigationDirection.Next for function PredictFocus
                //so we have to find it this way
                while ((nextRowCell as DataGridCell).PredictFocus(FocusNavigationDirection.Left) != null)
                    nextRowCell = (nextRowCell as DataGridCell).PredictFocus(FocusNavigationDirection.Left);
                //set new cell as next cell
                nextCell = nextRowCell;
            }

            //change current cell
            maindg.CurrentCell = new DataGridCellInfo(nextCell as DataGridCell);
            //change selected cell
            (nextCell as DataGridCell).IsSelected = true;
            // start edit mode
            maindg.BeginEdit();
        }
        //handl the default action of keydown
        e.Handled = true;
    }
}

Answer 1

你快到了。在 GotFocus() 上，只需将 CanUserAddRows 设置为 True。并在 LostFocus() 处理程序上将其设置为 False。

由于当焦点在网格内移动时也会调用 LostFocus 处理程序，您可以检查属性 IsKeyboardFocusWithin 以了解焦点是否在网格内。

private void maindg_GotFocus(object sender, RoutedEventArgs e)
{
    if (!maindg.CanUserAddRows)
    {
        maindg.CanUserAddRows = true;
    }
}

private void maindg_LostFocus(object sender, RoutedEventArgs e)
{
    if (!maindg.IsKeyboardFocusWithin && maindg.CanUserAddRows)
    {
        maindg.CanUserAddRows = false;
    }
}