Listview item tapped in xamarin.forms

Question

I'm trying to developp an App in Xamarin.Forms and XAML, and I need to capture an event when I tap on a LV. What I want the app to do is change the color of the Cell (or a StackLayout inside the cell) when the user tap on the Item on a list. I'm trying to implement the OnItemTapped property on the listview, but nothing happens when I press the Item. My code is quite simple:

Model: Product with 2 propeties, name and color.

public class Product: INotifyPropertyChanged
    {
        #region INotifyPropertyChanged implementation

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion

        public Product ()
        {
        }

        public string Name { get; set; }
        public bool Buy { get; set; }
        public  Color micolor { get; set; }

        //Método para actualizar los cambios
        protected virtual void OnPropertyChanged (string propertyName)
        {
            if (PropertyChanged == null)
                return;

            PropertyChanged (this, new PropertyChangedEventArgs (propertyName));
        }
    }

XAML: Only a list with two bindings: the name in a label, and the color in the SL

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="pruebalv.MyPage1">
    <ContentPage.Content>
     <ListView  x:Name="listView"
     ItemTapped="OmItemTapped"
     >

            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <StackLayout 
                        Orientation="Vertical"
                        BackgroundColor ="{Binding micolor}">
                                <Label Text="{Binding Name}"/>
                        </StackLayout>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </ContentPage.Content>
</ContentPage>

And behind .cs code: I create the products (it is only a sample) and implement the on item tapped. When item tapped, I want to change the color property of the item pressed.

public void OmItemTapped (object o, ItemTappedEventArgs e)
        {
            var dataItem = e.Item as Product;
            dataItem.micolor  = Color.Green;
            dataItem.Name  = "Tapped!!";

        }

The result that I get when I create a list is that nothing happens when I tap on an item.

Do am I missing something? As I've understood with the tutorials, only with the "itemtapped" roperty of the ListView, and the InotifyProperty... on the products, I'd see the results. Is it correct? Thanks!

Arkadiusz K Arkadiusz K · Accepted Answer · 2016-03-14T09:00:58

The important part in Xamarin.Forms MVVM infrastructure is that you need to explicitly invoke PropertyChanged when you are changing values of your properties.

Therefore, you need to amend your ViewModel code so that a PropertyChanged event is raised when the property changes. See the following example.

    private string name;
    public string Name 
    { 
        get { return name; }
        set 
        {
           name = value;
           OnPropertyChanged("Name");
        }
    }

And you have to do the same with your other properties

Listview item tapped in xamarin.forms

1 Answers