How-To: Use a Panel to Switch Views

Sometimes your application may need to switch between multiple views without the overhead of controls like Frame which support a navigation stack. In this case, it makes sense to define sectors of potential view content as regions and use another control to toggle the Visibility of the multiple views directly. This tutorial will show you how to use a Panel to switch between views.

Step-by-steps

Important

This guide assumes you used the template wizard or dotnet new unoapp to create your solution. If not, it is recommended that you follow the Creating an application with Uno.Extensions article for creating an application from the template.

1. Add necessary XAML namespaces

  • Update the Page element in MainPage.xaml to include XAML namespace mappings for Navigation and Uno Toolkit:

    xmlns:uen="using:Uno.Extensions.Navigation.UI"

  • Your Page element should now look like this:

    <Page x:Class="UsingPanelRegion.Views.MainPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:local="using:UsingPanelRegion.Views"
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
      mc:Ignorable="d"
      xmlns:uen="using:Uno.Extensions.Navigation.UI"
...

2. Define the view's layout

  • Add row definitions to the root Grid in MainPage.xaml:

    <Grid.RowDefinitions>
    <RowDefinition Height="Auto" />
    <RowDefinition Height="Auto" />
    <RowDefinition />
</Grid.RowDefinitions>

  • Define the control responsible for switching between views. In this case, we will place multiple Button controls in a StackPanel to represent the possible views:

    <StackPanel Grid.Row="1"
            HorizontalAlignment="Center"
            Orientation="Horizontal">
    <Button Content="One" />
    <Button Content="Two" />
    <Button Content="Three" />
</StackPanel>

  • Add a Grid containing several child panels and their content to the third row of the root Grid. These will represent the view content, and not all of them will be visible:

    <Grid Grid.Row="2">
    <Grid>
        <TextBlock Text="One"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center"/>
    </Grid>
    <Grid>
        <TextBlock Text="Two"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center" />
    </Grid>
    <Grid>
        <TextBlock Text="Three"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center" />
    </Grid>
</Grid>

  • Your Page element should now look like this:

    <Page x:Class="UsingPanelRegion.Views.MainPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:local="using:UsingPanelRegion.Views"
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
      mc:Ignorable="d"
      xmlns:uen="using:Uno.Extensions.Navigation.UI"
      Background="{ThemeResource MaterialBackgroundBrush}">

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
            <RowDefinition />
        </Grid.RowDefinitions>

        <StackPanel Grid.Row="1"
                    HorizontalAlignment="Center"
                    Orientation="Horizontal">
            <Button Content="One" />
            <Button Content="Two" />
            <Button Content="Three" />
        </StackPanel>

        <Grid Grid.Row="2">
            <Grid>
                <TextBlock Text="One"
                          FontSize="24"
                          HorizontalAlignment="Center"
                          VerticalAlignment="Center"/>
            </Grid>
            <Grid>
                <TextBlock Text="Two"
                          FontSize="24"
                          HorizontalAlignment="Center"
                          VerticalAlignment="Center" />
            </Grid>
            <Grid>
                <TextBlock Text="Three"
                          FontSize="24"
                          HorizontalAlignment="Center"
                          VerticalAlignment="Center" />
            </Grid>
        </Grid>
    </Grid>
</Page>

3. Set up navigation

  • We need to attach content regions for each view. Regions represent a container to where navigation will take place. The first step is to set the Region.Attached attached property to True on the parent Grid containing the views:

    <Grid Grid.Row="2"
      uen:Region.Attached="True">
    <Grid>
        <TextBlock Text="One"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center"/>
    </Grid>
    <Grid>
        <TextBlock Text="Two"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center" />
    </Grid>
    <Grid>
        <TextBlock Text="Three"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center" />
    </Grid>
</Grid>

  • Next, we need to set the Region.Name attached property on each child Grid to the corresponding view name:

    <Grid Grid.Row="2"
      uen:Region.Attached="True">
    <Grid uen:Region.Name="One">
        <TextBlock Text="One"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center"/>
    </Grid>
    <Grid uen:Region.Name="Two">
        <TextBlock Text="Two"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center" />
    </Grid>
    <Grid uen:Region.Name="Three">
        <TextBlock Text="Three"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center" />
    </Grid>
</Grid>

  • While you have designated the Grids above as regions, it is important to keep in mind the visual tree structure:

    • The parent Grid is the region container.
    • The child Grids are the regions.
    • The TextBlocks are the content of the regions.
Important

To specify one of these regions as a route, you must prefix the request name with "./" to indicate that the request involves a nested region. For example, if you want to navigate to the "One" view, you would use the request "./One" which includes the nested qualifier.

  • Set the Navigation.Request attached property on each Button control to what will be the route to a corresponding region. In this case, we should use the name that was defined above as the property value:

    <StackPanel Grid.Row="1"
            HorizontalAlignment="Center"
            Orientation="Horizontal">
    <Button Content="One"
            uen:Navigation.Request="./One" />
    <Button Content="Two"
            uen:Navigation.Request="./Two" />
    <Button Content="Three"
            uen:Navigation.Request="./Three" />
</StackPanel>

  • This will automatically set up navigation to the corresponding view when the Button.Click event is raised.

  • Since we want to toggle visibility of the views, we need to set the Region.Navigator attached property to Visibility:

    <Grid Grid.Row="2"
      uen:Region.Attached="True"
      uen:Region.Navigator="Visibility">
    <Grid uen:Region.Name="One">
        <TextBlock Text="One"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center"/>
    </Grid>
    <Grid uen:Region.Name="Two">
        <TextBlock Text="Two"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center" />
    </Grid>
    <Grid uen:Region.Name="Three">
        <TextBlock Text="Three"
                  FontSize="24"
                  HorizontalAlignment="Center"
                  VerticalAlignment="Center" />
    </Grid>
</Grid>

  • Finally, set the Visibility of the regions to Collapsed by default:

    <Grid Grid.Row="2"
      uen:Region.Attached="True"
      uen:Region.Navigator="Visibility">
    <Grid uen:Region.Name="One"
          Visibility="Collapsed">
        <TextBlock Text="One"
                   FontSize="24"
                   HorizontalAlignment="Center"
                   VerticalAlignment="Center"/>
    </Grid>
    <Grid uen:Region.Name="Two"
          Visibility="Collapsed">
        <TextBlock Text="Two"
                   FontSize="24"
                   HorizontalAlignment="Center"
                   VerticalAlignment="Center" />
    </Grid>
    <Grid uen:Region.Name="Three"
          Visibility="Collapsed">
        <TextBlock Text="Three"
                   FontSize="24"
                   HorizontalAlignment="Center"
                   VerticalAlignment="Center" />
    </Grid>
</Grid>

  • By establishing sectors of Page content as regions and setting a few attached properties, you have written a UI layout capable of navigating to views with Panel. Your completed MainPage.xaml should look like the code example below.

Code example

<Page x:Class="UsingPanelRegion.Views.MainPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:local="using:UsingPanelRegion.Views"
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
      mc:Ignorable="d"
      xmlns:uen="using:Uno.Extensions.Navigation.UI"
      xmlns:utu="using:Uno.Toolkit.UI"
      Background="{ThemeResource MaterialBackgroundBrush}">

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
            <RowDefinition />
        </Grid.RowDefinitions>

        <StackPanel Grid.Row="1"
                    HorizontalAlignment="Center"
                    Orientation="Horizontal">
            <Button Content="One"
                    uen:Navigation.Request="./One" />
            <Button Content="Two"
                    uen:Navigation.Request="./Two" />
            <Button Content="Three"
                    uen:Navigation.Request="./Three" />
        </StackPanel>

        <Grid uen:Region.Attached="True"
              uen:Region.Navigator="Visibility"
              Grid.Row="2">
            <Grid uen:Region.Name="One"
                  Visibility="Collapsed">
                <TextBlock Text="One"
                           FontSize="24"
                           HorizontalAlignment="Center"
                           VerticalAlignment="Center"/>
            </Grid>
            <Grid uen:Region.Name="Two"
                  Visibility="Collapsed">
                <TextBlock Text="Two"
                           FontSize="24"
                           HorizontalAlignment="Center"
                           VerticalAlignment="Center" />
            </Grid>
            <Grid uen:Region.Name="Three"
                  Visibility="Collapsed">
                <TextBlock Text="Three"
                           FontSize="24"
                           HorizontalAlignment="Center"
                           VerticalAlignment="Center" />
            </Grid>
        </Grid>
    </Grid>
</Page>

4. Switching between views

  • You can now switch between views by clicking on the Button controls - no Frame required! The Panel region will automatically toggle the visibility of the corresponding views.