BInding textColor in Xamarin-CodePudding

In a Xamarin app I’m trying to bind a textcolor with a property in Message model.

public class Message : INotifyPropertyChanged
{
    public string text { get; set; }
    public Color color { get; set; }
    public event PropertyChangedEventHandler PropertyChanged;
}

The task is, when I click on a label in a collectionview the text should change to Gray.

I can change the color in the ObservableCollection: this.messages = new ObservableCollection(); (that’s works, and if I delete an entry in the ObservableCollection the screen updates)

But when I change the color in the message model, the screen doesn’t update.

I use MVVMhelpers, and I would like to use that to solve the problem, if possible.

best regards..

CodePudding user response：

You could change the item color to gray when you click the item to triger the SelectionChanged event of CollectionView.

Xaml:

   <CollectionView ItemsSource="{Binding messages}" SelectionMode="Single" SelectionChanged="CollectionView_SelectionChanged">
        <CollectionView.ItemTemplate>
            <DataTemplate>
                <Label Text="{Binding text}" TextColor="{Binding color}"></Label>
            </DataTemplate>
        </CollectionView.ItemTemplate>
        </CollectionView>

Code behind:

 public partial class Page2 : ContentPage
{
    public ObservableCollection<Message> messages { get; set; }
    public Page2()
    {
        InitializeComponent();
        messages = new ObservableCollection<Message>()
        {
            new Message(){ text="A", color="Red"},
            new Message(){ text="B", color="Red"},
            new Message(){ text="C", color="Red"},

        };
        this.BindingContext = this;

    }

    private void CollectionView_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        var previousItem = e.PreviousSelection.FirstOrDefault() as Message;
        var currentItem = e.CurrentSelection.FirstOrDefault() as Message;
        currentItem.color = "Gray";

        if (previousItem!=null)
        {
            previousItem.color = "Red";
        }
    }
}
public class Message : INotifyPropertyChanged
{
    private string _text;
    public string text
    {
        get
        {
            return _text;
        }
        set
        {
            _text = value;
            OnPropertyChanged("text");
        }
    }
    private string _color;
    public string color
    {
        get
        {
            return _color;
        }
        set
        {
            _color = value;
            OnPropertyChanged("color");
        }
    }
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = "")
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

CodePudding user response：

super, great thanks.

I should also add

<DataTemplate x:DataType="{x:Type Models:Message}">