使用 Xamarin.forms 使用 RESTful API

Question

New to Xamarin.forms.

The following code should generate a list of games and bind it to a list view, but it does not. I am using the Refit library. The URL in Postman returns the JSON list as intended. Where should I start?

ISteamService.CS

using System.Collections.Generic;
using System.Threading.Tasks;
using Refit;

namespace PatchNotes
{

[Headers("Content-Type: application/json")]
public interface ISteamService
{
    [Get("/IPlayerService/GetOwnedGames/v1/?key=XXXXC&include_appinfo=1&steamid=XXXX")]
    Task<string> GetGames();
}

}

MainPage.xaml.cs

using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;
using Xamarin.Forms;
using Refit;

namespace PatchNotes
{
    public partial class MainPage : ContentPage
    {
    public MainPage()
    {
        InitializeComponent();
    }

    async void OnGetGamesClicked(object sender, System.EventArgs e)
    {
        var apiResponse = RestService.For<ISteamService>("https://api.steampowered.com");
        var games = await apiResponse.GetGames();

        GamesList.ItemsSource = games;

    }
}
}

MainPage.Xaml

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
         x:Class="PatchNotes.MainPage">
<ContentPage.Content>
    <StackLayout Padding="40">
         <Button Text="Get Games" Clicked="OnGetGamesClicked" 
BackgroundColor="Black" TextColor="White" 
HorizontalOptions="FillAndExpand"/>

          <ListView x:Name="GamesList">
            <ListView.ItemTemplate>
              <DataTemplate>
                <TextCell Text="{Binding Name}" />
              </DataTemplate>
            </ListView.ItemTemplate>
           </ListView>
    </StackLayout>
</ContentPage.Content>

Answer 1

According to this documentation GetOwnedGames will return a JSON (as Jason guessed correctly) with the following structure

{
    "game_count": <number of games>,
    "games": [ 
        {
            "appid": "...",
            "name": "...",
            "playtime_2weeks": ,
            "playtime_forever": ,
            "img_icon_url": "",
            "img_logo_url": "",
            "has_community_visible_stats": "" 
        }, ...]
}

You cannot simply assign this string to ItemsSource and expect Xamarin.Forms to figure out for you, you will have to take care how this is deserialized.

You will have to write a class that is used to deserialize your JSON string. Refit will do the deserialization, but you need a class to deserialize to anyway:

public class GamesList
{
    [JsonProperty("game_count")]
    public int GameCount { get; set; }

    [JsonProperty("games")]
    public List<Game> Games { get; set; }
}

public class Game
{
    [JsonProperty("appid")]
    public string AppId { get; set; }

    [JsonProperty("name")]
    public string Name { get; set; }

    [JsonProperty("playtime_2weeks")]
    public int PlayedMinutesInTheLastTwoWeeks { get; set; }

    // And so on. Depending on what you need.
}

(See the JSON.Net documentation on JsonProperty )

You can now redefine your ISteamService

[Headers("Content-Type: application/json")]
public interface ISteamService
{
    [Get("/IPlayerService/GetOwnedGames/v1/?key=XXXXC&include_appinfo=1&steamid=XXXX")]
    Task<GamesList> GetGames();
}

and use it from your OnGetGamesCicked like

var apiResponse = RestService.For<ISteamService>("https://api.steampowered.com");
var gamesList = await apiResponse.GetGames();

GamesList.ItemsSource = gamesList.Games;