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我想在Windows 8.1应用程序中创建一个自动完成框。Listbox的SelectionChanged事件被多次触发
XAML代码:
<Grid Background="#CCFFFFFF" VerticalAlignment="Top" >
<TextBox x:Name="tb" IsTextPredictionEnabled="False" Margin="30" Height="50" PlaceholderText="Enter text" VerticalAlignment="Top" Background="Transparent" BorderBrush="#333333" Foreground="#333333" FontWeight="SemiBold" />
<ListBox x:Name="lb" Background="Transparent" BorderBrush="#333333" MaxHeight="400" Visibility="Collapsed" Margin=" 30 80 30 30" VerticalAlignment="Top" >
<ListBox.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding data}" Foreground="#333333"/>
<TextBlock Text="{Binding data1}" Grid.Column="1" Margin="10 0 10 0" Foreground="#333333"/>
<StackPanel Orientation="Horizontal" Grid.Column="2">
<TextBlock Text="{Binding data2}" Margin="10 0 10 0" Foreground="#333333" />
<TextBlock Text="{Binding data3}" Foreground="#333333" />
</StackPanel>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
事件处理程序:
private async void tb_TextChanged(object sender, TextChangedEventArgs e)
{
lb.SelectionChanged -= lb_SelectionChanged;
if (tb.Text.Length < 1 || String.IsNullOrWhiteSpace(this.tb.Text))
{
return;
}
try
{
var list = await Data.getData();
lb.ItemsSource = list;
lb.Visibility = Windows.UI.Xaml.Visibility.Visible;
lb.SelectionChanged += lb_SelectionChanged;
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine(ex.Message.ToString());
}
}
void lb_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
tb.TextChanged -= tb_TextChanged;
if (lb.SelectedItem == null)
{
tb.TextChanged += tb_TextChanged;
lb.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
return;
}
tb.Text = lb.SelectedItem.ToString();
var item = (Data)lb.SelectedItem;
lb.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
tb.TextChanged += tb_TextChanged;
System.Diagnostics.Debug.WriteLine("SelectionChanged Called\n");
}
的问题是,如果我键入textbox
一个字符并从显示listbox
选择一个项目,所述SelctionChanged
事件引发一次。如果我键入两个字符,然后再次从显示框中选择一个项目,则会引发SelectionChanged
事件两次,依此类推。
为什么要在回调中删除并添加事件处理函数? – Dirk 2014-09-23 10:03:17
因为我不想,直到自动完成列表框填充了最新的名单和副芦荟的文本框 – thunderbird 2014-09-23 10:07:07
我通过删除列表框SelectionChanged事件'lb.SelectionChanged还挺固定问题的列表框可以进行选择 - = lb_SelectionChanged;前'仅仅指刚我添加了列表框选择更改事件'lb.SelectionChanged + = lb_SelectionChanged;'在'私人异步无效tb_TextChanged(对象发件人,TextChangedEventArgs e)'功能的try块中,但仍然不知道我以前做错了什么。 – thunderbird 2014-09-23 10:08:54