.net Maui Binding object doesnt show in app-CodePudding

Can anyone please tell me why I can't see the Tarefa.Condutor text variable in a label in my app? The Label in the app appears empty. What am I doing wrong? I think it's because of the Text="{Binding Tarefa.Condutor}" that doesn't binds correctly.

I have this code in .xaml file:

ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="GesfrotaTarefasApp.MVVM.Views.DashboardPage"
             xmlns:vm="clr-namespace:GesfrotaTarefasApp.MVVM.ViewModels"
             Title="DashboardPage">

    <ContentPage.BindingContext>
        <vm:DashboardViewModel />
    </ContentPage.BindingContext>

    <StackLayout BackgroundColor="White">
<Button x:Name="botao" Text="Carrega dados" Command="{Binding GetTarefaFakeCommand}" CommandParameter="{Binding CommandParam}"></Button>
        <Label x:Name="Teste" Text="{Binding Tarefa.Condutor}" FontSize="14" TextColor="Black"></Label>
</StackLayout>
</ContentPage>

And this code in .xaml.cs:

public partial class DashboardPage : ContentPage
{
    IConnectivity connectivity;

    public DashboardPage()
    {
        InitializeComponent();
        BindingContext = new DashboardViewModel();
    }
}

And this code in ViewModel.cs:

public partial class DashboardViewModel : BaseViewModel
    {
        HttpClient httpClient;

        private int commandParam = 1;
        public int CommandParam
        {
            get
            {
                return commandParam;
            }
            set
            {
                SetProperty(ref commandParam, value);
            }
        }

        private TarefaDTO tarefa;
        public TarefaDTO Tarefa
        {
            get
            {
                return tarefa;
            }
            set
            {
                SetProperty(ref tarefa, value);
            }
        }

        public DashboardViewModel()
        {
            Title = "Dashboard";
            httpClient = new HttpClient();

            tarefa = new TarefaDTO();
        }

public async Task<List<TarefaDTO>> GetTarefaFromFake()
        {
            return await Task.FromResult(new List<TarefaDTO>
                {
                    new TarefaDTO(){ Cliente = "Joao", Condutor = "Luis", DataCriacao = DateTime.Now, 
                        Estado = "Activo", IdTarefaEstado = 1, IdCondutor = 1, Id = 1 }, new TarefaDTO(){ Cliente = "Nuno", Condutor = "Fabio", DataCriacao = DateTime.Now, Estado = "Activo", IdTarefaEstado = 2, IdCondutor = 2, Id = 2 } , new TarefaDTO(){ Cliente = "Marta", Condutor = "Luisa", DataCriacao = DateTime.Now, Estado = "Activo", IdTarefaEstado = 3, IdCondutor = 3, Id = 3 }
                });
        }

        [RelayCommand]
        public async Task<TarefaDTO> GetTarefaFake(int? idTarefa)
        {
            var listaTarefas =  await GetTarefaFromFake();
            var novatarefa = listaTarefas.Where(t => t.Id == idTarefa).SingleOrDefault();
            return novatarefa;
        }

And my model is here:

public class TarefaDTO
    {
        public int Id { get; set; }
        public string Cliente { get; set; }
        public string Condutor { get; set; }
        public string Estado { get; set; }
        public DateTime DataCriacao { get; set; }
        public int IdCondutor { get; set; }
        public int IdTarefaEstado { get; set; }
    }

CodePudding user response：

There are several problems in your code.

1.You are setting your BindingContext in both the XAML and the code behind just as Jason said. You can remove one .

2.After creating a new instance of class TarefaDTO for variable tarefa , you didn't assign value for it, so you will get null for Label (<Label x:Name="Teste" Text="{Binding Tarefa.Condutor}"/>.

Here, as a test, you can initialize value for variable tarefa .

      public DashboardViewModel()
    {
        Title = "Dashboard";
        httpClient = new HttpClient();

        tarefa = new TarefaDTO();
        tarefa.Condutor ="test_Conductor";
    }

3.Suppose you want to get the data indexed by the first object(private int commandParam = 1;), and you can assign it to Tarefa, you can do like this:

  Tarefa = GetTarefaFake(index);

Based on your code, I created a demo, and it works on my side, you can refer to the following code:

      public class DashboardViewModel: BaseViewModel 
{

    HttpClient httpClient;

    private int commandParam = 1;
    public int CommandParam
    {
        get
        {
            return commandParam;
        }
        set
        {
            SetProperty(ref commandParam, value);
        }
    }


    private TarefaDTO tarefa;
    public TarefaDTO Tarefa
    {
        get
        {
            return tarefa;
        }
        set
        {
            SetProperty(ref tarefa, value);
        }
    }

    public ObservableCollection<TarefaDTO> items { get; set; }
    public ICommand MyCommand { private set; get; }

    public DashboardViewModel()
    {
        Title = "Dashboard";
        httpClient = new HttpClient();

        tarefa = new TarefaDTO();
        tarefa.Condutor = "test123456";

        items = new ObservableCollection<TarefaDTO>();
        MyCommand = new Command<int>(TestMethod);
    }

    private async void TestMethod(int obj)
    {
        Tarefa = await GetTarefaFake(obj);
    }

    public async Task<List<TarefaDTO>> GetTarefaFromFake()
    {
        return await Task.FromResult(new List<TarefaDTO>
            {
                new TarefaDTO(){ Cliente = "Joao", Condutor = "Luis", DataCriacao = DateTime.Now,
                    Estado = "Activo", IdTarefaEstado = 1, IdCondutor = 1, Id = 1 }, new TarefaDTO(){ Cliente = "Nuno", Condutor = "Fabio", DataCriacao = DateTime.Now, Estado = "Activo", IdTarefaEstado = 2, IdCondutor = 2, Id = 2 } , new TarefaDTO(){ Cliente = "Marta", Condutor = "Luisa", DataCriacao = DateTime.Now, Estado = "Activo", IdTarefaEstado = 3, IdCondutor = 3, Id = 3 }
            });
    }

    //[RelayCommand]
    public async Task<TarefaDTO> GetTarefaFake(int? idTarefa)
    {
        var listaTarefas = await GetTarefaFromFake();
        var novatarefa = listaTarefas.Where(t => t.Id == idTarefa).SingleOrDefault();
        return novatarefa;
    }
}

And the xaml is:

  <Button x:Name="botao" Text="Carrega dados" Command="{Binding MyCommand}" CommandParameter="{Binding CommandParam}"></Button>
  <Label x:Name="Teste" Text="{Binding Tarefa.Condutor}" FontSize="14" TextColor="Black"></Label>