CODEWITHSUNDEEP
xamarinxamarin.forms
user4458270
user4458270

Reputation:

Xamarin : Reverse the bool value in xamarin listview viewcell

I am new with xamarin, I am facing an issue in my xamarin forms project. I have two images inside listview-viewcell, one is for showing like and other for unlike. If the value of isUserLiked is true show the second image and otherwise show the first one. I try with !, but not working. Here is my code:

   <StackLayout HeightRequest="500">
        <ListView x:Name="ListView1" RowHeight="500" HorizontalOptions="CenterAndExpand">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                    <StackLayout
                            Orientation="Vertical">
                                <Image
                                    Source="unlike.png"
                                    IsVisible="{Binding !isUserLiked}"> 
                                </Image>
                                <Image
                                    Source="like.png"
                                    IsVisible="{Binding isUserLiked}">                                      
                                </Image>
                        </StackLayout>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
          </ListView>           
    </StackLayout>

How to reverse the binding value inside listview-viewcell. Anybody please suggest a solution with working code. Thanks in advance.

Upvotes: 1

Views: 2049

Answers (2)

Gerald Versluis
Gerald Versluis

Reputation: 34128

You could either work around it by creating another property in your ViewModel which gives you the inverse value.

A better way would be to use a ValueConverter, I have written a blog about it here. In the converter you could inverse the boolean value.

However there are also libraries that do that for you, they basically implement this converter for you.

Upvotes: 0

Ziyad Godil
Ziyad Godil

Reputation: 2680

You can't use operator in binding. Best way to use trigger for that like this :

<Image Source="unlike.png"> 
    <Image.Triggers>
        <DataTrigger TargetType="Image" Binding="{Binding isUserLiked}" Value="True">
            <Setter Property="Source" Value="like.png" />
        </DataTrigger>
    </Image.Triggers>
</Image>

Or

Another way to use converter like this:

Converter

public class InverseBoolConverter : IValueConverter, IMarkupExtension
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return !((bool)value);
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return value;
            //throw new NotImplementedException();
        }


        public object ProvideValue(IServiceProvider serviceProvider)
        {
            return this;
        }
    }

Now you can use in your Xaml code like this :

<Image Source="unlike.png" IsVisible="{Binding isUserLiked, Converter={Helpers:InverseBoolConverter}}" />

Don't forgot to add assembly in xaml header :

xmlns:Helpers="clr-namespace:MyNameSpace.Helpers"

Upvotes: 1

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