如何在window 10 uwp中折叠ExpandPanel

Question

我使用ExpandPanel来展开和折叠列表，如下所示。

 <local:ExpandPanel x:Name="test1" HeaderContent="Test1" Foreground="White" Margin="10,0,0,0" IsExpanded="False">
                                                <local:ExpandPanel.Content>
                                                    <TextBlock x:Name="yearlyAstrology" TextWrapping="Wrap"></TextBlock>
                                                </local:ExpandPanel.Content>
                                            </local:ExpandPanel>

    <local:ExpandPanel HeaderContent="Test2" Foreground="White" Margin="10,0,0,0" IsExpanded="False">
                                                <local:ExpandPanel.Content>
                                                    <TextBlock x:Name="guruAstrology" TextWrapping="Wrap"></TextBlock>
                                                </local:ExpandPanel.Content>
                                            </local:ExpandPanel>

现在，我想一次展开一个ExpandPanel。但在这种情况下，如果我展开一个面板并单击下一个面板，第一个面板不会折叠。因此，两个面板都仅处于展开状态。这看起来很烦人。我已经在C#端尝试过，如下所示。

test1.IsExpanded=false;

但它不起作用。我使用Expandanel.cs类，如下所示。

public ExpandPanel()
        {
            this.DefaultStyleKey = typeof(ExpandPanel);
        }

        private bool _useTransitions = true;
        private VisualState _collapsedState;
        private Windows.UI.Xaml.Controls.Primitives.ToggleButton toggleExpander;
        private FrameworkElement contentElement;

        public static readonly DependencyProperty HeaderContentProperty =
        DependencyProperty.Register("HeaderContent", typeof(object),
        typeof(ExpandPanel), null);

        public static readonly DependencyProperty IsExpandedProperty =
        DependencyProperty.Register("IsExpanded", typeof(bool),
        typeof(ExpandPanel), new PropertyMetadata(true));

        public static readonly DependencyProperty CornerRadiusProperty =
        DependencyProperty.Register("CornerRadius", typeof(CornerRadius),
        typeof(ExpandPanel), null);

        public object HeaderContent
        {
            get { return GetValue(HeaderContentProperty); }
            set { SetValue(HeaderContentProperty, value); }
        }

        public bool IsExpanded
        {
            get { return (bool)GetValue(IsExpandedProperty); }
            set { SetValue(IsExpandedProperty, value); }
        }

        public CornerRadius CornerRadius
        {
            get { return (CornerRadius)GetValue(CornerRadiusProperty); }
            set { SetValue(CornerRadiusProperty, value); }
        }

        private void changeVisualState(bool useTransitions)
        {
            if (IsExpanded)
            {
                if (contentElement != null)
                {
                    contentElement.Visibility = Visibility.Visible;
                }
                VisualStateManager.GoToState(this, "Expanded", useTransitions);
            }
            else
            {
                VisualStateManager.GoToState(this, "Collapsed", useTransitions);
                _collapsedState = (VisualState)GetTemplateChild("Collapsed");
                if (_collapsedState == null)
                {
                    if (contentElement != null)
                    {
                        contentElement.Visibility = Visibility.Collapsed;
                    }
                }
            }
        }

        protected override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            toggleExpander = (Windows.UI.Xaml.Controls.Primitives.ToggleButton)
                GetTemplateChild("ExpandCollapseButton");
            if (toggleExpander != null)
            {
                toggleExpander.Click += (object sender, RoutedEventArgs e) =>
                {
                    IsExpanded = !IsExpanded;
                    toggleExpander.IsChecked = IsExpanded;
                    changeVisualState(_useTransitions);
                };
            }
            contentElement = (FrameworkElement)GetTemplateChild("Content");
            if (contentElement != null)
            {
                _collapsedState = (VisualState)GetTemplateChild("Collapsed");
                if ((_collapsedState != null) && (_collapsedState.Storyboard != null))
                {
                    _collapsedState.Storyboard.Completed += (object sender, object e) =>
                    {
                        contentElement.Visibility = Visibility.Collapsed;
                    };
                }
            }
            changeVisualState(false);
        }

Answer 1

在给定的类中，IsExpanded属性在更改时不会影响任何内容。您可以在依赖项属性的定义中添加回调，以在属性更改时更改视觉状态：

public static readonly DependencyProperty IsExpandedProperty = 
    DependencyProperty.Register("IsExpanded", typeof(bool), typeof(ExpandPanel), 
        new PropertyMetadata(true, IsExpanded_Changed));

private static void IsExpanded_Changed(DependencyObject sender, DependencyPropertyChangedEventArgs args)
{
    var panel = (ExpandPanel)sender;
    panel.toggleExpander.IsChecked = IsExpanded;
    panel.changeVisualState(false);
}