Set visual state of a FlyoutItem to Selected-CodePudding

I am using Xamarin Forms and default ShellApp. I have FlyoutItems e.g.

<FlyoutItem Title="About" Icon="icon_about.png">
    <ShellContent Route="AboutPage" ContentTemplate="{DataTemplate local:AboutPage}" />
</FlyoutItem>
<FlyoutItem Title="Browse" Icon="icon_feed.png">
    <ShellContent Route="ItemsPage" ContentTemplate="{DataTemplate local:ItemsPage}" />
</FlyoutItem>

I don't like the default behavior, once clicked on an Item all other pages get poped from NavigationStack, so I changed that.

The problem I am facing now is marking the FlyoutItem as Selected.

I read that it is possible using VisualStateManager, but I don't know how to get the VisualElement and change its VisualState.

Any ideas how to achieve that?

Thanks

CodePudding user response：

A small example for your reference：

The following code defines two states for the left menu bar. It displays red in the normal state, and changes to green in the select state.

<Shell.Resources>
    <Style x:Key="FlyoutItemStyle" TargetType="Grid">
        <Setter Property="VisualStateManager.VisualStateGroups">
            <VisualStateGroupList>
                <VisualStateGroup x:Name="CommonStates">
                    <VisualState x:Name="Normal" >
                        <VisualState.Setters>
                            <Setter Property="BackgroundColor" Value="Green"/>
                        </VisualState.Setters>
                    </VisualState>
                    <VisualState x:Name="Selected">
                        <VisualState.Setters>
                            <Setter Property="BackgroundColor" Value="Red"/>
                        </VisualState.Setters>
                    </VisualState>
                </VisualStateGroup>
            </VisualStateGroupList>
        </Setter>
    </Style>
</Shell.Resources>
<Shell.ItemTemplate>
    <DataTemplate>
        <Grid HeightRequest="{x:OnPlatform Android=50}" Style="{StaticResource FlyoutItemStyle}">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="{x:OnPlatform Android=54, iOS=50}"></ColumnDefinition>
                <ColumnDefinition Width="*"></ColumnDefinition>
            </Grid.ColumnDefinitions>
            <Image Source="{Binding FlyoutIcon}"
                VerticalOptions="Center"
                HorizontalOptions="Center"
                HeightRequest="{x:OnPlatform Android=24, iOS=22}"
                WidthRequest="{x:OnPlatform Android=24, iOS=22}">
            </Image>
            <Label VerticalOptions="Center"
                    Text="{Binding Title}"
                    FontSize="{x:OnPlatform Android=14, iOS=Small}"
                    FontAttributes="Bold" Grid.Column="1">
                <Label.TextColor>
                    <OnPlatform x:TypeArguments="Color">
                        <OnPlatform.Platforms>
                            <On Platform="Android" Value="#D2000000" />
                        </OnPlatform.Platforms>
                    </OnPlatform>
                </Label.TextColor>
                <Label.Margin>
                    <OnPlatform x:TypeArguments="Thickness">
                        <OnPlatform.Platforms>
                            <On Platform="Android" Value="20, 0, 0, 0" />
                        </OnPlatform.Platforms>
                    </OnPlatform>
                </Label.Margin>
                <Label.FontFamily>
                    <OnPlatform x:TypeArguments="x:String">
                        <OnPlatform.Platforms>
                            <On Platform="Android" Value="sans-serif-medium" />
                        </OnPlatform.Platforms>
                    </OnPlatform>
                </Label.FontFamily>
            </Label>
        </Grid>
    </DataTemplate>
</Shell.ItemTemplate>

Here is the screenshot: