MAUI: ListView not updating in iOS (works on Android)

Question

I have a ListView, which is populated by an add function like so:

(Fig 1: empty list)

(Fig 2: one item added)

Data binding with MVVM:

<ListView ItemsSource="{Binding Persons}">  
      <Label Text="{Binding .}"  

The Entry field is bound to:

[ObservableProperty]  
public String attendee;  

Persons is an ObservableCollection in the viewmodel:

public ViewModel()  
        {  
            Persons = new ObservableCollection<String>();  
        }  
  
        [ObservableProperty]  
        ObservableCollection<String> persons;  

Button code:

[RelayCommand]  
void AddPerson()  
{  
    Persons.Add(Attendee);  
    Attendee = string.Empty;  
}  

Works on Android as shown above. Does not work on iOS, although the added persons are in the collection as they should. The list does just not get updated:

(Fig 3: list newer appears on iOS)

Answer 1

I tried to post that as a reply to @Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) , but it didn't work ¯_(ツ)_/¯

Thank you for your effort - Sorry for sharing possibly too less code.

You are right, Entry and Button are not inside the ListView:

< ... more stuff above ...>  
  
    <Label Text="Attendees"  
           Padding="0, 10"/>  
    <Border>  
        <VerticalStackLayout>  
            <ListView  
                ItemsSource="{Binding Persons}">  
                <ListView.ItemTemplate>  
                    <DataTemplate>  
                        <ViewCell>  
                            <Grid RowDefinitions="*, Auto">  
                                <Label Text="{Binding .}">  
                                <BoxView HeightRequest="1"/>  
                            </Grid>  
                         </ViewCell>  
                    </DataTemplate>  
                </ListView.ItemTemplate>  
            </ListView>  
            <Grid ColumnDefinitions="*, 50">  
                <Entry Placeholder="New attendee"  
                            Text="{Binding Attendee}"/>  
                <Button ImageSource="circle_plus_active.png"  
                        BackgroundColor="Transparent"  
                        Command="{Binding AddPersonCommand}"  
                        Grid.Column="1"/>  
            </Grid>  
         </VerticalStackLayout>  
    </Border>  

I tried your XAML, and if I use it isolated (=> takes full height), it works. As soon as I wrap it in a Border element or have other elements above, it does not. So this seems to be the restricting element in the iOS implementation.

As a workaround, I now use this:

           <Grid>  
                <Grid.RowDefinitions>  
                    <RowDefinition Height="*" />  
                    <RowDefinition Height="Auto" />  
                </Grid.RowDefinitions>  
                <ListView  
                    ItemsSource="{Binding Persons}">  
                    <ListView.ItemTemplate>  
                        <DataTemplate>  
                            <ViewCell>  
                                ...  
                             </ViewCell>  
                        </DataTemplate>  
                    </ListView.ItemTemplate>  
                </ListView>  
                <Grid ColumnDefinitions="*, 50"  
                      Grid.Row="1">  
                    <Entry Text="{Binding Attendee}"/>  
                    <Button ImageSource="circle_plus_active.png"  
                        BackgroundColor="Transparent"  
                        Command="{Binding AddPersonCommand}"  
                        Grid.Column="1"/>  
                </Grid>  
             </Grid>  

This makes the Border element take the remaining space on the screen, so there is some space for the ListView to build up.

Answer 2

The problem somehow solved itself, when I added a IsVisible property to my button. It seems, that this change in visibility does somehow trigger something to update the whole content that's wrapped inside the VerticalStackLayout.

Code:

                    <VerticalStackLayout>  
                        <ListView  
                            ItemsSource="{Binding Persons}"  
                            SelectionMode="None"  
                            SeparatorVisibility="None">  
                            <ListView.ItemTemplate>  
                                <DataTemplate>  
                                    <ViewCell>  
                                        <Grid RowDefinitions="*, Auto"  
                                              ColumnSpacing="5"  
                                              RowSpacing="8"  
                                              Padding="5">  
                                            <Label Text="{Binding .}"  
                                                   Style="{StaticResource MediumLabel}"  
                                                   TextColor="Black"  
                                                   Padding="0"/>  
                                            <BoxView HeightRequest="1"  
                                                     Margin="0"  
                                                     Grid.Row="1"  
                                                     Color="LightGray"/>  
                                        </Grid>  
                                     </ViewCell>  
                                </DataTemplate>  
                            </ListView.ItemTemplate>  
                        </ListView>  
                        <Grid ColumnDefinitions="*, Auto"  
                              Grid.Row="1">  
                            <Entry Placeholder="New attendee"  
                                   PlaceholderColor="DarkGray"  
                                   Style="{StaticResource SmallLabel}"  
                                   TextColor="Black"  
                                   Text="{Binding Attendee}"/>  
                            <Button ImageSource="circle_plus_active.png"  
                                    IsVisible="{Binding btnVisible}"  
                                    BackgroundColor="Transparent"  
                                    Command="{Binding AddPersonCommand}"  
                                    Grid.Column="1"/>  
                        </Grid>  
                     </VerticalStackLayout>