question

bilelmiled-6268 avatar image
0 Votes"
bilelmiled-6268 asked JarvanZhang-MSFT edited

i want that my list view reloard automatically

Hi my problem is i wnat when i add a new row it will be appear directly
i have this model

  namespace hereminder.Models
        
     {
         [Table("Pins")]
         public class Pins 
         {
        
             [PrimaryKey,MaxLength(250), Unique]
             public string Label { get; set; }
        
             [MaxLength(250)]
             public string Todo { get; set; }
        
             [Unique]
             public double Positionlat { get; set; }
             [Unique]
             public double Positionlon { get; set; }
                
         }}

and this is the xaml of list view


 <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
              x:Class="hereminder.listofinterest"
              xmlns:ios="clr-namespace:Xamarin.Forms.PlatformConfiguration.iOSSpecific;assembly=Xamarin.Forms.Core"
              BackgroundColor="#B6E13D"
              ios:Page.UseSafeArea="true"
              IconImageSource="pen.png">
     <ContentPage.Content>
         <StackLayout BackgroundColor="#B6E13D">
    
               
    
             <StackLayout  BackgroundColor="White">
                 <ListView x:Name="listViewEvent" HasUnevenRows="True" BackgroundColor="White" SeparatorVisibility="Default">
                     <ListView.ItemTemplate>
                         <DataTemplate>
                             <ViewCell>
    
                                 <StackLayout Margin="5">
    
                                     <Grid BackgroundColor="WhiteSmoke" ColumnSpacing="0" >
                                         <Grid.ColumnDefinitions>
                                             <ColumnDefinition Width="auto" />
                                             <ColumnDefinition Width="auto" />
                                         </Grid.ColumnDefinitions>
                                           
    
                                         <Label Grid.Column="1"
                    Grid.Row="0"
                    Text="{Binding Label}"
                    FontSize="20"
                   />
    
                                         <Label Grid.Column="2"
                    Grid.Row="1"
                    Text="{Binding Todo}" 
                    FontSize="20"
                    />
                                         <ImageButton Grid.Column="2"
                               
                                Command="{Binding Path=BindingContext.UpdateCommand, Source={x:Reference Name=listViewEvent}}"  
                                        CommandParameter="{Binding Label}"
                                                      />
                                            
                                     </Grid>
                                 </StackLayout>
                             </ViewCell>
                         </DataTemplate>
                     </ListView.ItemTemplate>
                 </ListView>
         </StackLayout>
     </ContentPage.Content>
 </ContentPage>



and this is the class file of listview


 namespace hereminder
 {
     [XamlCompilation(XamlCompilationOptions.Compile)]
     public partial class listofinterest 
     {
         public List<Pins> list;
         public ListView lv;
    
         public listofinterest()
         {
             InitializeComponent();
    
             list = App.pinsRepo.GetAllPins();
    
    
             listViewEvent.ItemsSource = list;
    
    
                
             Padding = new Thickness(0, 20, 0, 0);
    
             
    
         }
    
     }
 }

i need help please

dotnet-xamarinformsdotnet-xamarinessentials
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1 Answer

JarvanZhang-MSFT avatar image
0 Votes"
JarvanZhang-MSFT answered JarvanZhang-MSFT edited

Hello,​

Welcome to our Microsoft Q&A platform!

Hi, @bilelmiled-6268 To update the ListView automatically when new items are added, besides using an ObservableCollection, the model class also needs to implement the INotifyPropertyChanged interface to raise the PropertyChanged event.

Try to set data binding using MVVM pattern to update the data at runtime, check the code:

public partial class TestPage : ContentPage
{
    TestViewModel viewModel;
    public TestPage()
    {
        InitializeComponent();

        viewModel = new TestViewModel();
        BindingContext = viewModel;
    }
}

public class TestModel : INotifyPropertyChanged
{
    private string theContent;
    public string TheContent
    {
        get
        {
            return theContent;
        }
        set
        {
            if (theContent != value)
            {
                theContent = value;
                NotifyPropertyChanged("TheContent");
            }
        }
    }

    protected virtual void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public event PropertyChangedEventHandler PropertyChanged;
}

public class TestViewModel
{
    public ObservableCollection<TestModel> ContentCollection { get; set; }
    public TestViewModel()
    {
        ContentCollection = new ObservableCollection<TestModel>();
        //add the data
    }
}

Set data binding for the listView in xaml

<ListView x:Name="listview" ItemsSource="{Binding DataCollection}">
    <ListView.ItemTemplate>
        <DataTemplate>
            <ViewCell>
                <StackLayout>
                    <Label Text="{Binding TheContent}"/>
                </StackLayout>
            </ViewCell>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

Related doc: https://docs.microsoft.com/en-us/xamarin/xamarin-forms/xaml/xaml-basics/data-bindings-to-mvvm

Best Regards,

Jarvan Zhang



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