Xamarin Forms Editing Item with SQL

Question

I have an application where items are added to a collection view and then you can tap on that item where a detail page comes up. With this detail page, you can edit the title and description given and then it should update in the collection view. However, when changes are made to the item, the item is not changed within the observable collection. How do I go about this?

Here is my xaml for the detail page:

<StackLayout Spacing="5" Padding="10" AnchorY="0.5">
    <!--<Label Text="Title:" FontSize="Medium" FontAttributes="Bold" TextColor="White"/>-->
    <Editor Text="{Binding Text}" FontSize="Title" TextColor="White"/>
    <!--<Label Text="Note:" FontSize="Medium" FontAttributes="Bold" TextColor="White"/>-->
    <Editor Text="{Binding Description}" FontSize="Small" TextColor="White"/>
    <Grid ColumnDefinitions="*,*,*">
        <Label Grid.Column="0" Grid.ColumnSpan="2" Text="Due Date:" FontSize="Medium" FontAttributes="Bold" TextColor="White" VerticalOptions="CenterAndExpand" HorizontalOptions="StartAndExpand"/>
        <Label Grid.Column="0" Grid.ColumnSpan="2" Padding="50,4,0,0" Text="{Binding DueDate}" FontSize="Small" TextColor="White" VerticalOptions="CenterAndExpand" HorizontalOptions="CenterAndExpand"/>
    </Grid>
    <Button Text="Save"  
            Command="{Binding SaveChangesCommand}"
            VerticalOptions="EndAndExpand"
            HorizontalOptions="EndAndExpand"
            BackgroundColor="Black" 
            BorderWidth="1.5"
            BorderColor="White"
            CornerRadius="50">
    </Button>
</StackLayout>

Here is my DataBaseService:

public async Task UpdateItem(Item item)
{
    var databasePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "MyData3.db");
    var db = new SQLiteAsyncConnection(databasePath);

    await db.UpdateAsync(item);
    OnUpdatedItem?.Invoke();
}

OnUpdateItem?.Invoked();

private void LocalDatabaseService_OnUpdatedItem()
{
    _ = ExecuteLoadItemsCommand();
}

and here is the OnSaveChanges

private async void OnSaveChanges(Item item)
{
        Text = Text;
        Description = Description;
        DueDate = DueDate;

    await LocalDatabaseService.UpdateItem(item);

    await Shell.Current.GoToAsync("..");
}

LoadItems:

async Task ExecuteLoadItemsCommand()
{
    IsBusy = true;

    try
    {
        Items.Clear();
        var items = await LocalDatabaseService.GetAllItems();
        foreach (var item in items)
        {
            Items.Add(item);
        }
    }
    catch (Exception ex)
    {
        Debug.WriteLine(ex);
    }
    finally
    {
        IsBusy = false;
    }
}

Item Model:

public class Item : INotifyPropertyChanged
{
    [PrimaryKey, AutoIncrement]
    public int Id { get; set; }
    public string Text
    {
        get { return Text; }
        set
        {
            Text = value;
            if (Text != value)
            {
                OnPropertyChanged("Text");
                Text = value;
            }
        }
    }
    public string Description 
    { 
        get { return Description; }
        set 
        { Description = value;
            if(Description != value)
            {
                OnPropertyChanged("Description");
                Description = value;
            }
        }
    }
    public DateTime DueDate { get; set; }

    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

any help is appreciated, Thanks.

Answer 1

From the code you posted, we found the parameter in method OnSaveChanges is useless since it is always null.

You can change your code like this in class ItemDetailViewModel:

    public Command SaveChangesCommand { get; }
    public ItemDetailViewModel()
    {
        SaveChangesCommand = new Command(OnSaveChanges);
    }

And method OnSaveChanges:

    private async void OnSaveChanges()
    {

        Item item = new Item();
        item.Id = Int32.Parse(ItemId);
        item.Text = Text;
        item.Description = Description;
        item.DueDate = DueDate;

        await LocalDatabaseService.UpdateItem(item);

        await Shell.Current.GoToAsync("..");
    }