CODEWITHSUNDEEP
xamarin.formsnavigationxamarin.forms.entry
13ackspace
13ackspace

Reputation: 5

How to pass data using PopAsync?

I have the following situation: I have an app, where I want to create notes using a special page for it. I have VM with ObservableCollection NoteItems with all the notes. When I want to create a new note, I add a new note to this ObservableCollection and pass this new note using BindingContext

    var editingPage = new EditingPage();
    editingPage.BindingContext = NoteItems[NoteItems.Count - 1].Text; 
    Application.Current.MainPage.Navigation.PushAsync(editingPage);

In the editing page I have an Entry field

       <Entry
         x:Name="EdtingPageEntryField"
         Text="{Binding Text}"
         Placeholder="Enter a note"
       />

, which is Binding his text with the Text parameter of a NoteItem. The problem is that if I change the text in entry field, it does not automatically apply to a Text parameter of a NoteItem. That is why I want to pass this text when I close this EditingPage(go back to the MainPage). So the question is, how can I pass this Text parameter to a NoteItem element from NoteItems ObservableCollection, which is located in VM.

UPD. The value of NoteItem, which is located in NoteItems does not change

UPD2. I was wrong about the value of NoteItem, it has been changed, but the new value does not display on MainPage, that is why I used INotifyPropertyChanged, but it did not work.

Here is Note Item class

public class NoteItem
    {

        public event PropertyChangedEventHandler PropertyChanged;

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

        private string text;
        public string Text 
        { 
            get { return text; } 
            set 
            { 
                if(text != value) 
                { 
                    text = value; 
                    NotifyPropertyChanged();
                }
            } 
        }

And MainPage.xaml:

<ContentPage.BindingContext>
        <local:NoteItemViewModel/>
    </ContentPage.BindingContext>

    <FlexLayout>
        
        <ListView ItemsSource="{Binding NoteItems}">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <Label Text="{Binding Text}"/>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
        
    </FlexLayout>
'''

Upvotes: 0

Views: 676

Answers (1)

Jason
Jason

Reputation: 89214

in order to dynamically update the UI, your model must implement INotifyPropertyChanged

public class NoteItem : INotifyPropertyChanged
{
  ...
}

simply adding a PropertyChanged method is not the same as implementing INotifyPropertyChanged. You must add the interface to the class definition so that the binding mechanism knows that your class has implemented it

Upvotes: 1

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