Xamarin forms: Load more items without button click - xamarin.forms

Question

Dears,
I am implementing load more items to listview without a button.
My code:
public partial class DashBoardPage : ContentPage
{
ObservableCollection<string> Items;
bool isLoading;
public DashBoardPage()
{
InitializeComponent();
Items = new ObservableCollection<string>();
var listview = new ListView();
listview.ItemsSource = Items;
listview.ItemAppearing += (sender, e) =>
{
if (isLoading || Items.Count == 0)
return;
//hit bottom!
if (e.Item.ToString() == Items[Items.Count - 1])
{
LoadItems();
}
};
LoadItems();
}
public async void LoadItems()
{
isLoading = true;
HttpClient client = new HttpClient();
var response = await client.GetAsync("My Url");
string tweetJson = await response.Content.ReadAsStringAsync();
UserTweetResponse userTweetResponse = new UserTweetResponse();
if (tweetJson != "")
{
userTweetResponse = JsonConvert.DeserializeObject<UserTweetResponse>(tweetJson.ToString());
foreach (var tweet in userTweetResponse.userTweetsList)
{
Items.Add(tweet.ToString());
}
}
ListView1.ItemsSource = userTweetResponse.userTweetsList;
isLoading = false;
}
}
I refer the following link and confused with the for loop inside LoadItems():
https://montemagno.com/load-more-items-at-end-of-listview-in/
for (int i = 0; i < 20; i++)
{
Items.Add (string.Format("Item {0}", Items.Count));
}
In my case I am using itemSource property to bind the response to list view.
My model class:
public class UserTweetResponse
{
public List<UserTweetsList> userTweetsList { get; set; }
}
public class UserTweetsList
{
public int tweetId { get; set; }
public string tweetData { get; set; }
public string createdTime { get; set; }
public int commentCount { get; set; }
public int likeCount { get; set; }
public int flagCount { get; set; }
public string mediaUrl { get; set; }
public string tweetUser { get; set; }
public bool userLiked { get; set; }
public bool userFlagged { get; set; }
public bool isMediaUrlNull { get { return string.IsNullOrEmpty(mediaUrl); } }
}
How can I fix this?
Thanks in advance

Answer 1

You need to add your new tweets to your Items collection
public async void LoadItems()
{
isLoading = true;
HttpClient client = new HttpClient();
var response = await client.GetAsync("My Url");
string tweetJson = await response.Content.ReadAsStringAsync();
UserTweetResponse userTweetResponse = new UserTweetResponse();
if (tweetJson != "")
{
userTweetResponse = JsonConvert.DeserializeObject<UserTweetResponse>(tweetJson.ToString());
foreach (var tweet in userTweetResponse.userTweetsList)
{
Items.Add(tweet);
}
}
isLoading = false;
}
because the Observable collection is the ListView item source the new items will appear in the list.

Answer 2

Pasete this whole:
using System;
using System.Diagnostics;
using System.Net.Http;
using Newtonsoft.Json;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
using System.Collections.ObjectModel;
using System.Threading.Tasks;
namespace SmartTweet
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class DashBoardPage : ContentPage
{
int i = 1;
bool loadMore;
ObservableCollection<UserTweetsList> Items =new ObservableCollection<SmartTweet.UserTweetsList>();
bool isLoading;
UserTweetResponse userTweetResponse;
public DashBoardPage()
{
InitializeComponent();
ListView1.ItemAppearing += (sender, e) =>
{
if (isLoading || Items!=null && Items.Count == 0)
return;
//hit bottom
if (userTweetResponse.userTweetsList!=null && userTweetResponse.userTweetsList.Count>0)
{
UserTweetsList item = userTweetResponse.userTweetsList[userTweetResponse.userTweetsList.Count - 1];
if ((e.Item as UserTweetsList).tweetId.ToString() == item.tweetId.ToString())
{
Debug.WriteLine("Enter bottom");
loadMore = true;
UserTweetsList();
}
}
};
}
protected async override void OnAppearing()
{
await UserTweetsList();
base.OnAppearing();
}
async void ButtonClicked(Object sender, EventArgs e)
{
loadMore = true;
// await UserTweetsList();
}
public async Task UserTweetsList()
{
isLoading = true;
if (loadMore)
{
i = i + 1;
}
int countInInt = i * 3;
try
{
string applicationId = "1";
string siteId = "5";
string userId = "225";
string ownedBy = "me";
string period = "before";
string count = countInInt.ToString();
DateTime dt = DateTime.Now.ToLocalTime();
string date = dt.Year.ToString() + "-" + dt.Month.ToString() + "-" + dt.Day.ToString() + " " + dt.Hour.ToString() + ":" + dt.Minute.ToString() + ":" + dt.Second.ToString() + "." + dt.Millisecond.ToString();
HttpClient client = new HttpClient();
var response = await client.GetAsync("web service url");
string tweetJson = await response.Content.ReadAsStringAsync();
Debug.WriteLine("tweetList:>" + tweetJson);
userTweetResponse = new UserTweetResponse();
if (tweetJson != "")
{
userTweetResponse = JsonConvert.DeserializeObject<UserTweetResponse>(tweetJson.ToString());
foreach (var tweet in userTweetResponse.userTweetsList)
{
if (!Items.Contains(tweet))
{
Items.Add(tweet);
}
//Items.Add(tweet.ToString());
}
}
ListView1.ItemsSource = userTweetResponse.userTweetsList;
isLoading = false;
if (userTweetResponse.userTweetsList.Count == 0)
{
//loadMoreButton.IsVisible = false;
blue_holo_circle.IsVisible = false;
blueLine.IsVisible = false;
}
else
{
//loadMoreButton.IsVisible = true;
blue_holo_circle.IsVisible = true;
blueLine.IsVisible = true;
}
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine("Exception:>" + ex);
}
}
}
}