UserControl BringIntoView()无法正常工作 [英] UserControl BringIntoView() not working properly

问题描述

背景: 我在ScrollViewer和ContentControl中定义了usercontrol，ContentControl始终可见，并且其中有一个Button，单击按钮时将设置到Visible，并且当usercontrol显示(Visiblility="Visible")时，我希望将其滚动到视图中.我有

Background: I have a usercontrol defined in a ScrollViewer along with a ContentControl, the ContentControl will be visible all the time, and within it there is a Button, when the button is clicked will set the usercontrol to Visible, and when the usercontrol shows (Visiblility="Visible") I want it to be scrolled into the view. I have

XAML

<ScrollViewer  VerticalScrollBarVisibility="Auto"  MaxHeight="465">
  <Grid>
    <Grid.RowDefinitions>
      <RowDefinition Height="*" />
      <RowDefinition Height="*" />
    </Grid.RowDefinitions>
    <ContentControl Content="{Binding MyOtherViewModel}"  Width="960" ></ContentControl>
    <local:MyView  IsVisibleChanged="MyView_IsVisibleChanged" Grid.Row="1" Visibility="{Binding IsNonCompliant, Converter={StaticResource BooltoVisible}, UpdateSourceTrigger=PropertyChanged}" />        
</ScrollViewer>

背后的代码

private void MyView_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            (sender as Control).BringIntoView();        
        }

问题: :这不起作用，或更准确地说，我的usercontrol首先滚动到视图中，然后在眨.

Problem: this is not working, or more precisely, my usercontrol scrolled into the view first then revert back to the bottom of the ScrollViewer in a blink.

奇怪的事情: 在调用BringIntoView之前显示messagebox会正确地将我的usercontrol显示在视图中间

Weird thing: show a messagebox before calling BringIntoView will correctly display my usercontrol into the middle of the view

当前的黑客解决方案: ，您甚至可以看到Window在loaded

private void MyView_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
            {
                Window ss = new Window();
                ss.Loaded += new RoutedEventHandler(ss_Loaded);
                ss.ShowDialog();
                (sender as Control).BringIntoView();        
            }   

private void ss_Loaded(object sender, RoutedEventArgs e)
        {
            (sender as Window).Close();
        }

问题: :我知道还必须进行其他操作，但是我无法识别它，但是我真的很想知道当窗口显示时发生了什么用ShowDialog吗?这是因为它刷新window以便BringIntoView仅在加载usercontrol之后才会发生吗? (不是我现在遇到的问题:先出现BringIntoView，然后刷新window，然后将scrollbar放回顶部).对我的问题正确的解决方法是什么?

Question: I know there must be something else going on, but I just can't identify it, but I really want to know what happened when a window showing with ShowDialog? Is this because it refreshes the window so that the BringIntoView will happen only after the usercontrol been loaded? (Not as the problem I have now: BringIntoView happened first, and then the window get refreshed and put the scrollbar back to the top). And what is the correct fix for my problem?

推荐答案

看起来像BringIntoView在我的Usercontrol渲染之前被调用，结果，当它完全渲染时，scrollbar还原为顶部(正如我在问题中所描述的).还要感谢 @Evgeny 提出的另一个问题的答案，我现在有了更好的解决方案(也许没有hack了?).还是想看看是否有更好的解决方案.

It looks like BringIntoView called before my Usercontrol getting rendered, as a result when it gets fully rendered, the scrollbar is revert back to the top (as I have described in my question). And thanks for the answer from @Evgeny posted for another question, I get a better solution now (less hack maybe?). Still want to see if there are better solutions.

   private void MyView_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
   {
        var border = (FrameworkElement)sender;
        if (border.IsVisible)
        {
            //Window ss = new Window();
            //ss.Loaded += new RoutedEventHandler(ss_Loaded);
            //ss.ShowDialog();
            using (BackgroundWorker bg = new BackgroundWorker())
            {
                bg.DoWork += new DoWorkEventHandler(bg_DoWork);
                bg.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bg_RunWorkerCompleted);
                Tuple<FrameworkElement, double> b = new Tuple<FrameworkElement, double>(border, border.Height);
                bg.RunWorkerAsync(b);
            }
        }
   }       

    private void bg_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        (e.Result as UserControl).BringIntoView();
    }

    private void bg_DoWork(object sender, DoWorkEventArgs e)
    {   
        int maxwait = 300 //not scrolled to the view is not a disaster, but if the program hangs forever it will be a disaster, so set this to prevent that from happening
        while (maxwait!=0 
               && 
               (e.Argument as Tuple<FrameworkElement, double>).Item1.ActualHeight != (e.Argument as Tuple<FrameworkElement, double>).Item2)
        {
            Thread.Sleep(1);
            maxwait --;
        }
        e.Result = (e.Argument as Tuple<FrameworkElement, double>).Item1;
    }  

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