Question

我正在尝试使用ContextActions从组列表视图中删除一个项目；但是，当我单击它时，它什么也没做

我知道如何从列表视图中删除一个项目，但不删除属于列表视图中的组的项目

This is #CODE side of the code
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
using XamarinForm3.MODELSID;

namespace XamarinForm3
{
    // Learn more about making custom code visible in the Xamarin.Forms previewer
    // by visiting https://aka.ms/xamarinforms-previewer
    [DesignTimeVisible(true)]
    public partial class MainPage : ContentPage
    {
        private ObservableCollection<ContactIDGroup> _contactsID; //List<ContactIDGroup> will not be able to update the screen
        public MainPage()
        {
            InitializeComponent();

            _contactsID = new ObservableCollection<ContactIDGroup> {
                new ContactIDGroup("V", "V")
                {
                    new ContactID {Name="Victor", ImageUrl="http://lorempixel.com/100/100/people/1" }

                },
                new ContactIDGroup("J", "J")
                {
                    new ContactID {Name="Jon", ImageUrl="http://lorempixel.com/100/100/people/2", Status="Hello"}

                }
            };
            listViewID.ItemsSource = _contactsID;
        }

        void Handle_ItemSelected(object sender, Xamarin.Forms.SelectedItemChangedEventArgs e)
        {
            var contact = e.SelectedItem as ContactID;
            DisplayAlert("Selected", contact.Name, "OK");
        }

        void Handle_ItemTapped(object sender, Xamarin.Forms.ItemTappedEventArgs e)
        {
            var contact = e.Item as ContactID;
            DisplayAlert("Tapped", contact.Name, "OK");
        }

        void CallID_Clicked(object sender, System.EventArgs e)
        {
            var menuItemID = sender as MenuItem;
            var contactID = menuItemID.CommandParameter as ContactID;
            DisplayAlert("CallID", contactID.Name, "OK");
        }
        void DeleteID_Clicked(object sender, System.EventArgs e)
        {
            var menuItemID = sender as MenuItem;
            var contactID = menuItemID.CommandParameter as ContactIDGroup;
            _contactsID.Remove(contactID);
        }
    }
}

This XAML side
<?xml version="1.0" encoding="utf-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:local="clr-namespace:XamarinForm3" x:Class="XamarinForm3.MainPage">

    <ListView x:Name="listViewID"
              IsGroupingEnabled="true"
              GroupDisplayBinding="{Binding TitleID}"
              GroupShortNameBinding="{Binding ShortTitleID}"
              ItemSelected="Handle_ItemSelected"
              ItemTapped="Handle_ItemTapped">
        <ListView.ItemTemplate>
            <DataTemplate>
                <ImageCell Text="{Binding Name}" Detail="{Binding Status}" ImageSource="{Binding ImageUrl}">
                    <ImageCell.ContextActions>
                        <MenuItem Text="CallID" Clicked="CallID_Clicked" CommandParameter="{Binding .}"/>
                        <MenuItem Text="DeleteID" Clicked="DeleteID_Clicked" IsDestructive="true" CommandParameter="{Binding .}"/>
                    </ImageCell.ContextActions>
                </ImageCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</ContentPage>

This is ContactID class
using System;
namespace XamarinForm3.MODELSID
{
    public class ContactID
    {
        public string Name { get; set; }
        public string Status { get; set; }
        public string ImageUrl { get; set; }
    }
}

This is ContactIDGroup class
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

namespace XamarinForm3.MODELSID
{
    public class ContactIDGroup : ObservableCollection<ContactID>
    {

        public string TitleID { get; set; }
        public string ShortTitleID { get; set; }

        public ContactIDGroup(string titleID, string shortTitleID)
        {
            TitleID = titleID;
            ShortTitleID = shortTitleID;
        }
    }
}

我想要的是当我按下MenuItem中的Delete选项时，它实际上消失了。

Answer 1

尝试一下：

var contact = (sender as VisualElement).BindingContext as ContactID;

Answer 2

原因：

var contactID = menuItemID.CommandParameter

将返回 ContactID ，而不是 ContactIDGroup

解决方案：

请参阅以下代码

void DeleteID_Clicked(object sender, System.EventArgs e)
{
   var menuItemID = sender as MenuItem;
   var contactID = menuItemID.CommandParameter as ContactID;

   for (int i=0;i<_contactsID.Count;i++)
   {
       ContactIDGroup contactIDs = _contactsID[i];
       for (int j = 0; j < contactIDs.Count; j++)
       {
         if (contactIDs[j] == contactID )
          {
            _contactsID[i].RemoveAt(j);
          }
       }
   }

}

Answer 3

private void DeleteClicked(object sender, EventArgs e)
    {
        var contactId = (sender as MenuItem).CommandParameter as ContactId;
        for(int i = 0; i < _contactsId.Count; i++)
        {
            for(int j = 0; j<_contactsId[i].Count; j++)
            {
                if(_contactsId[i][j] == contactId)
                {
                    _contactsId[i].Remove(contactId);
                }
            }
        }
        
    }

如何从列表视图组中删除项目？

3 个答案: