how-to-maintain-the-expanded-and-collapsed-states-of-nodes-when-navigating-in-.net-maui-treeview

This repository demonstrates how to maintain the expanded and collapsed states of nodes when navigating in the .NET MAUI TreeView (SfTreeView) control. It provides a sample implementation that uses a model property and event handlers to persist and restore the expansion state of each node, ensuring a consistent user experience across navigation and data reloads.

Sample

You can keep the expanded and collapsed state of the TreeViewNode after navigation by using a model class property and updating its value whenever the node is expanded or collapsed.

XAML

<ContentPage.Resources>
    <ResourceDictionary>
        <local:ExpanderIconVisibilityConverter x:Key="ExpanderIconVisibilityConverter"/>
        <local:ExpanderIconConverter x:Key="ExpanderIconConverter" />
        <local:ExpanderStateConverer x:Key="ExpanderStateConverer" />
    </ResourceDictionary>
</ContentPage.Resources>

<ContentPage.Content>
    <Grid RowDefinitions="*">
        <treeView:SfTreeView x:Name="treeView" Grid.Row="1"
                           ExpanderWidth="0"
                           Indentation="40"
                           ExpandActionTarget="Node"
                           ChildPropertyName="SubFiles"
                           ItemTemplateContextType="Node" 
                           ItemsSource="{Binding ImageNodeInfo}">
            <treeView:SfTreeView.Behaviors>
                <local:TreeViewBehavior/>
            </treeView:SfTreeView.Behaviors>
            <treeView:SfTreeView.ItemTemplate>
                <DataTemplate>
                    <Grid x:Name="grid" RowSpacing="0" >
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="40" />
                            <ColumnDefinition Width="40" />
                            <ColumnDefinition Width="*" />
                        </Grid.ColumnDefinitions>
                        <Image Grid.Column="0" Source="{Binding IsExpanded, Converter={StaticResource ExpanderIconConverter}}"
                        IsVisible="{Binding HasChildNodes,Converter={StaticResource ExpanderIconVisibilityConverter}}"/>
                        <Image Grid.Column="1" Source="{Binding Content.ImageIcon}" VerticalOptions="Center" HorizontalOptions="Center" HeightRequest="35" WidthRequest="35"/>
                        <Grid Grid.Column="2" RowSpacing="1" Padding="1,0,0,0" VerticalOptions="Center">
                            <Label LineBreakMode="NoWrap" Text="{Binding ., Converter={x:StaticResource ExpanderStateConverer}}" VerticalTextAlignment="Center"/>
                        </Grid>
                    </Grid>
                </DataTemplate>
            </treeView:SfTreeView.ItemTemplate>
        </treeView:SfTreeView>
    </Grid>
</ContentPage.Content>

Requirements to run the demo

To run the demo, refer to System Requirements for .NET MAUI.

Troubleshooting:

Path too long exception

If you are facing path too long exception when building this example project, close Visual Studio and rename the repository to short and build the project.

License

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