How to Update ObservableCollection Item Dynamically in MAUI

March 22, 2023

I have a CollectionView layer that takes 2 variables. One of them should be updated dynamically, but I couldn’t figure out how to do it.

I am accessing ObservableCollection via ModelView and changing the value of the variable but it is not updating on the screen.

Thanks for helping.

Here is my sample code

<CollectionView x:Name="collectionview1" ItemsSource="{Binding PosesObserv}">
            <CollectionView.ItemTemplate>
                <DataTemplate>
                    <ContentView>
                        <StackLayout>
                            <Slider x:Name="slider" Minimum="0" Maximum="1"   WidthRequest="100"></Slider>
                            <Label Text="{Binding Source={x:Reference slider}, Path=Value, StringFormat='[{0:0.00000}]'}"></Label>
                            <Label Text="{Binding poseValue}"></Label> // this value should be updated
                        </StackLayout>
                    </ContentView>
                </DataTemplate>
            </CollectionView.ItemTemplate>
</CollectionView>

public partial class MainPage : ContentPage
{

    PosesView pView = new PosesView();
    
    public MainPage()
    {
            Task.Factory.StartNew(InitializeComponent);
            BindingContext = pView;
            Task.Factory.StartNew(StartListener);
    
    }
    
    
    public class Poses
    {
            private string _pose;
            public string pose
            {
                get => _pose; set
                {
                    _pose = value;
                }
            }
    
            private double _poseValue;
            public double poseValue
            {
                get => _poseValue; set
                {
                    _poseValue = value;
                }
            }
    }
    
    
    
    
    public class PosesView : INotifyPropertyChanged
    {
            public event PropertyChangedEventHandler PropertyChanged;
            public Dictionary<string, double> posesDict = new() // There is lots of value
            
            public PosesView()
            {
                _PosesObserv = getSliderC();
            }
    
            public List<Poses> poseList = new();
            private ObservableCollection<Poses> getSliderC()
            {
                poseList.Clear();
                foreach (KeyValuePair<string, double> entry in posesDict)
                {
                    poseList.Add(new Poses { pose = entry.Key, poseValue = entry.Value });
                }
                ObservableCollection<Poses> poseCollection = new(poseList);
                return poseCollection;
            }
    
            private ObservableCollection<Poses> _PosesObserv;
            public ObservableCollection<Poses> PosesObserv
            {
                get => _PosesObserv;
                set
                {
                    if (_PosesObserv != value)
                    {
                        this._PosesObserv = value;
                        OnPropertyChanged();
                    }
    
                }
            }
    
    
            public void OnPropertyChanged([CallerMemberName] String propertyName = "")
            {
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
            }
    }
    
    private void StartListener()
    {
        UdpClient udpListener = new(3001);
        IPEndPoint ep = new(IPAddress.Parse("127.0.0.1"), 3001);
        List<Poses> poseList = new();
        try
        {
            while (true)
            {
                Thread.Sleep(1000);
                byte[] bytes = udpListener.Receive(ref ep);
                string[] s = Encoding.ASCII.GetString(bytes, 0, bytes.Length).Split("///");
                string[] s1 = s.Skip(1).ToArray();

                pView.PosesObserv.FirstOrDefault(i => i.pose == "ExamplePose").poseValue = Convert.ToDouble(s1[6]);

            }
        }

        catch (SocketException e)
        {
            Debug.WriteLine(e);
        }
        finally
        {
            udpListener.Close();
        }
    }
    
}