用于删除 Xamarin.Forms 中当前 ListView 行的按钮

Question

我正在使用数据绑定从 SQLite 数据库中填充 ListView。我希望用户能够按下按钮并删除当前行。

Page1.xaml:

  <ListView x:Name="recentUserList" Margin="20,0" VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand">
            <ListView.ItemTemplate>
                <DataTemplate >
                    <ViewCell>
                        <Frame Padding="5" Margin="0,0,0,5">
                            <Grid HeightRequest="50" HorizontalOptions="FillAndExpand" VerticalOptions="Start">
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="*"/>
                                    <ColumnDefinition Width="Auto"/>
                                    <ColumnDefinition Width="Auto"/>
                                    <ColumnDefinition Width="*"/>
                                </Grid.ColumnDefinitions>
                                <Label Grid.Column="0" Text="{Binding UserName}"/>
                                <Button Grid.Column="3" Text="Delete" Clicked="BtnDelete_Clicked" />
                            </Grid>
                        </Frame>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

Page1.cs:

protected override void OnAppearing()
{
        base.OnAppearing();
        recentUserList.ItemsSource = App.Database.GetUserList();
}

private void BtnDelete_Clicked(object sender, EventArgs e)
{
        var user = sender as User;
        recentUserList.Remove(user);
}

数据库：

public List<User> GetUserList()
{
    return database.Query<User>("SELECT * FROM User;");
}

User.cs:

 public class User: INotifyPropertyChanged
 {
        [PrimaryKey, AutoIncrement]
        public int ID { get; set; }
        private string userName;
        public string UserName
        {
            get
            {
                return userName;
            }
            set
            {
                if (userName!= value)
                {
                    userName = value;
                    OnPropertyChanged("UserName");
                }
            }
        }
}

这会导致 Remove in recentUserList.Remove(user); in Page1.cs 的以下错误。

Error CS7036: There is no argument given that corresponds to the required formal parameter 'value' of 'CollectionExtensions.Remove<TKey, TValue>(IDictionary<TKey, TValue>, TKey, out TValue)'

我怎样才能做到可以点击按钮删除给定的 ListView item/row?

Answer 1

sender 对象的类型为 Button 而不是 User，尽管在本例中 BindingContext 属性的类型为 User :

private void BtnDelete_Clicked(object sender, EventArgs e)
{
        var btn = sender as Button;
        var user = btn.BindingContext as User;
        //recentUserList.Remove(user);
}

另外，recentUserList 是一个 ui 元素 (ListView)，它没有 .Remove() 方法。您需要做的是将它 ItemsSource 绑定到您将调用 .Remove() 方法的 ObservableCollection。

我强烈邀请您阅读 related documentation

Answer 2

首先使用一个ObservableCollection

ObservableCollection<User> users;

protected override void OnAppearing()
{
        base.OnAppearing();
        recentUserList.ItemsSource = users = new ObservableCollection<User>(App.Database.GetUserList());
}

然后从数据源中删除 user，UI 将更新

private void BtnDelete_Clicked(object sender, EventArgs e)
{
        var btn = sender as Button;
        var user = btn.BindingContext as User;
        users.Remove(user);
}

用于删除 Xamarin.Forms 中当前 ListView 行的按钮

Button to delete current ListView Row in Xamarin.Forms

c#

xamarin

xamarin.forms

xamarin.forms.listview