You can fetch data from a web server and store it on a local server for Xamarin.Forms SfListView. You can refer to the document regarding offline JSON with ListView from here.
You can also refer the following article.
XAML
Create Xamarin.Forms application with SfListView.
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:ListViewXamarin"
xmlns:syncfusion="clr-namespace:Syncfusion.ListView.XForms;assembly=Syncfusion.SfListView.XForms"
xmlns:data="clr-namespace:Syncfusion.DataSource;assembly=Syncfusion.DataSource.Portable"
x:Class="ListViewXamarin.MainPage" Padding="{OnPlatform iOS='0,40,0,0'}">
<ContentPage.BindingContext>
<local:ListViewModel/>
</ContentPage.BindingContext>
<ContentPage.Content>
<StackLayout>
<Grid BackgroundColor="#2196F3" HeightRequest="40">
<Label Text="To Do Items" x:Name="headerLabel" TextColor="White" FontAttributes="Bold" VerticalOptions="Center" HorizontalOptions="Center" />
</Grid>
<syncfusion:SfListView x:Name="listView" ItemSize="60" GroupHeaderSize="50" BackgroundColor="#FFE8E8EC" ItemsSource="{Binding Items}">
<syncfusion:SfListView.ItemTemplate >
<DataTemplate>
...
</DataTemplate>
</syncfusion:SfListView.ItemTemplate>
<syncfusion:SfListView.DataSource>
<data:DataSource>
<data:DataSource.GroupDescriptors>
<data:GroupDescriptor PropertyName="userId"/>
</data:DataSource.GroupDescriptors>
</data:DataSource>
</syncfusion:SfListView.DataSource>
<syncfusion:SfListView.GroupHeaderTemplate>
<DataTemplate>
...
</DataTemplate>
</syncfusion:SfListView.GroupHeaderTemplate>
</syncfusion:SfListView>
</StackLayout>
</ContentPage.Content>
</ContentPage>C#
Fetch data and download from the web server.
-
Using the HTTPClient.GetAsync method, retrieve data from the web server for the specified URL.
-
The HTTPContent.ReadAsStreamAsync returns the data in stream format.
-
Use Environment.GetFolderPath method to create a local path to store the retrieved data and combine 4. the path with the file name using Path.Combine method.
-
The FileInfo.OpenWrite creates a write only stream and write to the local file stream using CopyToAsync method.
namespace ListViewXamarin
{
public class DataServices
{
private static HttpClient httpClient;
public DataServices()
{
httpClient = new HttpClient();
}
/// <summary>
/// Fetches data from web server and write it to the local file.
/// </summary>
/// <returns>Returns true, if data fetched from webserver and downloaded to the local location.</returns>
public async Task<bool> DownloadJsonAsync()
{
try
{
var url = "https://jsonplaceholder.typicode.com/todos"; //Set your REST API url here
//Sends request to retrieve data from the web service for the specified Uri
var response = await httpClient.GetAsync(url);
using (var stream = await response.Content.ReadAsStreamAsync()) //Reads data as stream
{
//Gets the path to the specified folder
var localFolder = System.Environment.GetFolderPath(System.Environment.SpecialFolder.LocalApplicationData);
var newpath = Path.Combine(localFolder, "data.json"); // Combine path with the file name
var fileInfo = new FileInfo(newpath);
//Creates a write-only file stream
using (var fileStream = fileInfo.OpenWrite())
{
await stream.CopyToAsync(fileStream); //Reads data from the current stream and write to destination stream (fileStream)
}
}
}
catch (OperationCanceledException e)
{
System.Diagnostics.Debug.WriteLine(@"ERROR {0}", e.Message);
return false;
}
catch (Exception e)
{
System.Diagnostics.Debug.WriteLine(@"ERROR {0}", e.Message);
return false;
}
return true;
}
}
}C#
Read data from local file and set it to collection.
namespace ListViewXamarin
{
public class ListViewModel : INotifyPropertyChanged
{
private dynamic items;
private bool isDownloaded;
public dynamic Items
{
get { return items; }
set
{
items = value;
OnPropertyChanged("Items");
}
}
public DataServices DataService { get; set; }
public ListViewModel()
{
DataService = new DataServices();
GetDataAsync();
}
private async void GetDataAsync()
{
isDownloaded = await DataService.DownloadJsonAsync();
if (isDownloaded)
{
var localFolder = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
var fileText = File.ReadAllText(Path.Combine(localFolder, "data.json"));
//Read data from the local file path and set it to the collection bound to the ListView.
Items = JsonConvert.DeserializeObject<dynamic>(fileText);
}
}
}
}