ScrollViewer不會滾動到頂部

Question

ScrollViewer不會滾動到頂部 。 有什么線索嗎？

用戶控件

 public class AniScrollViewer : ScrollViewer
    {
        //Register a DependencyProperty which has a onChange callback
        public static DependencyProperty CurrentVerticalOffsetProperty = DependencyProperty.Register("CurrentVerticalOffset", typeof(double), typeof(AniScrollViewer), new PropertyMetadata(new PropertyChangedCallback(OnVerticalChanged)));
        public static DependencyProperty CurrentHorizontalOffsetProperty = DependencyProperty.Register("CurrentHorizontalOffsetOffset", typeof(double), typeof(AniScrollViewer), new PropertyMetadata(new PropertyChangedCallback(OnHorizontalChanged)));

        //When the DependencyProperty is changed change the vertical offset, thus 'animating' the scrollViewer
        private static void OnVerticalChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            AniScrollViewer viewer = d as AniScrollViewer;
            viewer.ScrollToVerticalOffset((double)e.NewValue);
        }

        //When the DependencyProperty is changed change the vertical offset, thus 'animating' the scrollViewer
        private static void OnHorizontalChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            AniScrollViewer viewer = d as AniScrollViewer;
            viewer.ScrollToHorizontalOffset((double)e.NewValue);
        }


        public double CurrentHorizontalOffset
        {
            get { return (double)this.GetValue(CurrentHorizontalOffsetProperty); }
            set { this.SetValue(CurrentHorizontalOffsetProperty, value); }
        }

        public double CurrentVerticalOffset
        {
            get { return (double)this.GetValue(CurrentVerticalOffsetProperty); }
            set { this.SetValue(CurrentVerticalOffsetProperty, value); }
        }

    }

主要代號

  public partial class Window1 : Window
    {
        Random rnd = new Random();
        private const int _ITEM_COUNT = 20;
        Point relativePoint;
        Storyboard sb = new Storyboard();
        Button btn;

        public Window1()
        {
            InitializeComponent();
            sb.Completed += (o, s) => ScrollItems();

            //Create some buttons ;)
            for (int i = 0; i < _ITEM_COUNT; i++)
            {
                Button btn = CreateButton(i);
                ListViewItem item = new ListViewItem();
                item.Tag = btn;
                item.Content = "Button " + i.ToString();
                cbJumpTo.Items.Add(item);
                mainContent.Children.Add(btn);
            }

            labelH.Content = mainViewer.Height;
        }

        /// <summary>
        /// Create a new button...  There are some properties that need to be set, since this is a 
        /// SIMPLE demo, this should be fine.
        /// </summary>
        /// <param name="index">index of the button</param>
        /// <returns>Created button</returns>
        private Button CreateButton(int index)
        {
            Button btn = new Button();
            btn.Content = "Button " + index.ToString();
            int h = rnd.Next(30, 500);
            btn.Height = h;
            btn.Margin = new Thickness(5);
            return btn;
        }
        /// <summary>
        /// Animate the scrollviewer the the selected item from the combobox
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnAnimate_Click(object sender, RoutedEventArgs e)
        {
            //Get the position of the button located in the tag
            btn = ((ListViewItem)cbJumpTo.SelectedItem).Tag as Button;
            relativePoint = btn.TransformToAncestor(mainContent).Transform(new Point(0, 0));
            ScrollToPosition(relativePoint.X, relativePoint.Y);
        }

        /// <summary>
        /// Create a new animation to the x,y offset.  I beleive you need the have .NET 3.5 SP1 installed for
        /// this to work.  If you don't you can't call Storyboard.SetTarget.
        /// </summary>
        /// <param name="x">X position</param>
        /// <param name="y">Y position</param>
        private void ScrollToPosition(double x, double y)
        {

            DoubleAnimation vertAnim = new DoubleAnimation();
            vertAnim.From = mainViewer.VerticalOffset;
            vertAnim.To = y;
            vertAnim.DecelerationRatio = .2;
            vertAnim.Duration = new Duration(TimeSpan.FromMilliseconds(25000));
            DoubleAnimation horzAnim = new DoubleAnimation();
            horzAnim.From = mainViewer.HorizontalOffset;
            horzAnim.To = x;
            horzAnim.DecelerationRatio = .2;
            horzAnim.Duration = new Duration(TimeSpan.FromMilliseconds(1000));

            sb.Children.Add(vertAnim);
            sb.Children.Add(horzAnim);
            Storyboard.SetTarget(vertAnim, mainViewer);
            Storyboard.SetTargetProperty(vertAnim, new PropertyPath(AniScrollViewer.CurrentVerticalOffsetProperty));
            Storyboard.SetTarget(horzAnim, mainViewer);
            Storyboard.SetTargetProperty(horzAnim, new PropertyPath(AniScrollViewer.CurrentHorizontalOffsetProperty));
            sb.Begin(this);

        }


        private void ScrollItems()
        {
            mainViewer.ScrollToTop(); // It does not scroll to top
        }

    }

XAML

 <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"></RowDefinition>
            <RowDefinition Height="50"></RowDefinition>
        </Grid.RowDefinitions>
        <local:AniScrollViewer x:Name="mainViewer" Grid.Row="0" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
            <StackPanel x:Name="mainContent"></StackPanel>
        </local:AniScrollViewer>
        <StackPanel Margin="10,10,0,10" Grid.Row="1" Orientation="Horizontal" Width="258">
            <ComboBox x:Name="cbJumpTo" Margin="5" Width="84.884"></ComboBox>
            <Button x:Name="btnAnimate" Margin="5" Click="btnAnimate_Click">Start Animation</Button>
            <Label x:Name="labelH" Content="Label"/>
        </StackPanel>
    </Grid>

Answer 1

我只是用這段代碼

private void ScrollItems()
        {
           ScrollToPositionTop(0,0); // It does not scroll to top
        }

 private void ScrollToPositionTop(double x, double y)
        {

            DoubleAnimation vertAnim = new DoubleAnimation();
            vertAnim.From = mainViewer.VerticalOffset;
            vertAnim.To = y;
            vertAnim.DecelerationRatio = .2;
            vertAnim.Duration = new Duration(TimeSpan.FromMilliseconds(0));
            DoubleAnimation horzAnim = new DoubleAnimation();
            horzAnim.From = mainViewer.HorizontalOffset;
            horzAnim.To = x;
            horzAnim.DecelerationRatio = .2;
            horzAnim.Duration = new Duration(TimeSpan.FromMilliseconds(0));

            sb.Children.Add(vertAnim);
            sb.Children.Add(horzAnim);
            Storyboard.SetTarget(vertAnim, mainViewer);
            Storyboard.SetTargetProperty(vertAnim, new PropertyPath(AniScrollViewer.CurrentVerticalOffsetProperty));
            Storyboard.SetTarget(horzAnim, mainViewer);
            Storyboard.SetTargetProperty(horzAnim, new PropertyPath(AniScrollViewer.CurrentHorizontalOffsetProperty));
            sb.Begin(this);

        }