绑定的ItemsControl在显示之前没有更新

本文关键字：更新 显示 ItemsControl 绑定 | 更新日期: 2023-09-27 17:51:04

我有一个UserControl，它由几个绑定的ItemsControl和strings组成，根据按下的按钮，显示不同的数据。下面是Button的一个点击事件的示例:

private void LeftPreviousScoresButton_Click(object sender, RoutedEventArgs e)
{
    if (m_previousScoresWindow.Visibility == Visibility.Visible)
    {
        m_previousScoresWindow.Hide();
    }
    else
    {
        WindowTitle = "Left Side";
        PreviousScoresA = m_previousLeftWristErosionScoresReaderA;
        PreviousScoresB = m_previousLeftWristErosionScoresReaderB;
        m_previousScoresWindow.Show();
    }
}

有几个这样的单击事件侦听器，它们为WindowTitle、PreviousScoresA和PreviousScoresB分配相关的数据。然后UserControl像这样绑定到它们:

<ItemsControl Height="Auto" Width="Auto"
              ItemsSource="{Binding ElementName=ParentForm, Path=PreviousScoresA}" 
              Grid.Row="1" />
<ItemsControl Height="Auto" Width="Auto"
              ItemsSource="{Binding ElementName=ParentForm, Path=PreviousScoresB}" 
              Grid.Row="2" />
<TextBlock FontSize="16" FontWeight="Bold" Height="25" 
           Margin="5" HorizontalAlignment="Center" Foreground="Black" 
           Text="{Binding ElementName=ParentForm, Path=PreviousScoresWindowTitle}" />

然而，当打开窗口时，旧数据在用当前数据更新之前会显示一秒钟。我甚至尝试在Window上调用Hide()时添加这些调用，但似乎没有帮助:

WindowTitle = String.Empty;
PreviousScoresA = new ObservableCollection<PreviousScoreData>();
PreviousScoresB = new ObservableCollection<PreviousScoreData>();

是否有任何方法可以确保Show()直到绑定数据更新后才被调用?谢谢。

绑定的ItemsControl在显示之前没有更新

由于您使用的是ObservableCollection，因此不应该重新初始化集合。相反，它应该被清除，然后添加新的值;这有助于在使用ObservableCollection时保持集合同步。

根据你的代码样本，这是一个有点黑暗的镜头;如果您在隐藏时清除集合，然后用新值重新填充它们，那么您应该得到所需的效果:

private void LeftPreviousScoresButton_Click(object sender, RoutedEventArgs e)
{
  if (m_previousScoresWindow.Visibility == Visibility.Visible)
  {
    m_previousScoresWindow.Hide();
    WindowTitle = string.Empty;
    PreviousScoresA.Clear();
    PreviousScoresB.Clear();
  }
  else
  {
    WindowTitle = "Left Side";
    // do not re-initialize the collection; clear and add new values
    // PreviousScoresA = m_previousLeftWristErosionScoresReaderA;
    // PreviousScoresB = m_previousLeftWristErosionScoresReaderB;
    ReFillScores(PreviousScoresA, m_previousLeftWristErosionScoresReaderA);
    ReFillScores(PreviousScoresB, m_previousLeftWristErosionScoresReaderB);
    m_previousScoresWindow.Show();
  }
}
private void ReFillScores (ObservableCollection<PreviousScoreData> collection, IEnumerable<PreviousScoreData> values)
{
  collection.Clear();
  foreach(PreviousScoreData d in values)
  {
    collection.Add(d);
  }
}
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