如何动态更改标签的颜色？ Xamarin

Question

I got this code below but I can't figure out how to make the selected label be turned into blue background colour and white text instead of what it has in unselected mode. There can only be 1 journey selected at time, and the one that is selected needs to be modified. I figured I could use datatriggers or behaviours. I can figure out how to change the button in the command, but how would I change the other buttons? that gets unselected into gray?

<CollectionView Grid.Row="1" Grid.Column="0" ItemsSource="{Binding JourneyItems}" SelectionMode="Single"  ItemsLayout="{x:Static ListItemsLayout.HorizontalList}">
    <CollectionView.ItemTemplate>
        <DataTemplate>
            <StackLayout Orientation="Horizontal" >
                <StackLayout Margin="10,0,10,0" BackgroundColor="LightGray"  VerticalOptions="Fill"  Orientation="Horizontal" >
                    <Label Text="{Binding Name}"  TextColor="{StaticResource ThemeBkColor}" VerticalTextAlignment="Center" VerticalOptions="Center" />
                </StackLayout>

                <StackLayout.GestureRecognizers>
                    <TapGestureRecognizer Command="{Binding Path=ViewModel.SwitchJourneyCommand, Source={x:Reference ThisJourneysPage}}"
                        CommandParameter = "{Binding .}" NumberOfTapsRequired="1"/>
                </StackLayout.GestureRecognizers>
            </StackLayout>
        </DataTemplate>
    </CollectionView.ItemTemplate>
</CollectionView>

Answer 1

You just need to add a Selected property to your JourneyItems model and then even a BackgroundColor.

public class JourneyItem {
    // more stuff

    public bool Selected { get; set; }

    public Color BackgroundColor => Selected ? Color.Blue : Color.Gray;

    public Color TextColor => Selected ? Color.White : Color.Black;
}

Then bind the BackgroundColor and TextColor to change to color X when Selected is true and color Y otherwise.

<Label Text="{Binding Name}"  TextColor="{Binding TextColor}"  BackgroundColor="{Binding BackgroundColor}"/>

Finally, in ViewModel.SwitchJourneyCommand set your selected model to true and all other models to false .

public void OnJourneyCommand(JourneyItem selectedItem) {
    foreach(JourneyItem item in JourneyItems) {
        item.Selected = item.Id == selectedItem.Id;
    }
}