Binding properties to a ListView in Xamarin, does not update the View

user_8357883 0
Viewed 384

I am having trouble, with binding properties to a ListView in Xamarin Forms. What I am trying to do is:

        {
            InitializeComponent();
            //Task.Run(async () => await GetTaskDetails());


            GetTasks();

        }

        ObservableCollection<XMCTasks> _userTasks;

        private async void GetTasks()
        {
            using (var client = new HttpClient())
            {
                string userId = "";
                if(Application.Current.Properties["userId"] != null)
                {
                    userId = Application.Current.Properties["userId"].ToString();
                }
                var uri = "http://diplomaxmcws-dev.us-east-2.elasticbeanstalk.com/api/Tasks/GetUserTasks?userId=" + userId;
                var result = await client.GetStringAsync(uri);
                var TaskList = JsonConvert.DeserializeObject<List<XMCTasks>>(result);
                UserTasks = new ObservableCollection<XMCTasks>(TaskList);
            }
        }

        public ObservableCollection<XMCTasks> UserTasks
        {
            get
            {
                return _userTasks;
            }
            set
            {
                _userTasks = value;
                OnPropertyChanged();
            }
        }

Getting a list of objects from a Rest API call, and after that binding those objects to a ListView:

<ListView ItemsSource="{Binding UserTasks}">
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <ViewCell>
                            <ViewCell.View>
                                <StackLayout>
                                   <!-- <Label Text="{Binding XMCTask_Id, StringFormat='XMCTask_Id: {0:F0)}'}"></Label> -->
                                    <Label Text="{Binding Task_Name, StringFormat='Task_Name: {0:F0)}'}" TextColor="Black" FontSize="Medium"></Label>
                                    <!-- <Label Text="{Binding Task_Description, StringFormat='Task_Description: {0:F0)}'}"></Label>
                                    <Label Text="{Binding Creator_Id, StringFormat='Creator_Id: {0:F0)}'}"></Label> 
                                     <Label Text="{Binding Referencer_Id, StringFormat='Referencer_Id: {0:F0)}'}"></Label>
                                    <Label Text="{Binding XMCPune_Id, StringFormat='XMCPune_Id: {0:F0)}'}"></Label>
                                    <Label Text="{Binding XMCProjekt_Id, StringFormat='XMCProjekt_Id: {0:F0)}'}"></Label>
                                    <Button Text="{Binding XMCTipologjia_Id, StringFormat='XMCTipologjia_Id: {0:F0)}'}"></Button>-->
                                </StackLayout>
                            </ViewCell.View>
                        </ViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>

I don't know if it has to do with the lifecycle of a Xamarin Forms Page. Just to let you know, this page gets loaded after a successful login. Since the process of getting the results from the web service is async it may be possible something to get messed up. Any approach is much appreciated.

xamarin.forms xamarin listview c#
1 Answers

The BindingContext property of the target object must be set to the source object.

If you want to use ItemsSource="{Binding UserTasks} in the xaml,you should add BindingContext = this;in your page.cs constructor as Jason said above.

or you could define x:Name for your ListView in xaml,then set ItemSource in your page.cs:

<ListView x:Name="listview">
  ...
</ListView>


private async void GetTasks()
    {
        using (var client = new HttpClient())
        {
            string userId = "";
            if(Application.Current.Properties["userId"] != null)
            {
                userId = Application.Current.Properties["userId"].ToString();
            }
            var uri = "http://diplomaxmcws-dev.us-east-2.elasticbeanstalk.com/api/Tasks/GetUserTasks?userId=" + userId;
            var result = await client.GetStringAsync(uri);
            var TaskList = JsonConvert.DeserializeObject<List<XMCTasks>>(result);
            UserTasks = new ObservableCollection<XMCTasks>(TaskList);
            listview.ItemsSource = UserTasks;
        }
    }
user_107686530
Related