C# AndroidClient Identity Server

使用C#开发Android客户端时，需要通过Identity Server 4进行认证。需要安装程序包：IdentityModel.OidcClient，在程序中需要配置：

 private OidcClientOptions _options;
_options = new OidcClientOptions
            {
                Authority = _authority,
                Policy= new Policy()
                {

                   Discovery = new DiscoveryPolicy { RequireHttps = false } ,
                },

                ClientId = "mymobileclient",
                Scope = "openid profile poemapi",
                RedirectUri = "io.identitymodel.native://callback",
                Browser = new ChromeCustomTabsBrowser(this),
                
            };

Login方法中，初始化OidcClient并登录:

                var oidcClient = new OidcClient(_options);
                var result = await oidcClient.LoginAsync();
                _state = new State 
                { 
                    IdToken = result.IdentityToken,
                    AccessToken = result.AccessToken,
                    RefreshToken = result.RefreshToken,
                    User = result.User,
                    Error = result.Error,
                };

调用Web API

                var client = new HttpClient();
                client.SetBearerToken(_state.AccessToken);

在认证管理中配置相关的client。

还需要编写自定义的浏览器接口，启动移动设备的浏览器完成认证：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Android.App;
using Android.Content;
using Android.Graphics;
using Android.OS;
using Android.Runtime;
using Android.Support.CustomTabs;
using Android.Views;
using Android.Widget;
using IdentityModel.OidcClient.Browser;

namespace AndroidClient
{
    public class ChromeCustomTabsBrowser : IBrowser
    {
        private readonly Activity _context;
        private readonly CustomTabsActivityManager _manager;

        public ChromeCustomTabsBrowser(Activity context)
        {
            _context = context;
            _manager = new CustomTabsActivityManager(_context);
        }

        public Task<BrowserResult> InvokeAsync(BrowserOptions options, CancellationToken cancellationToken = default(CancellationToken))
        {
            var task = new TaskCompletionSource<BrowserResult>();

            var builder = new CustomTabsIntent.Builder(_manager.Session)
               .SetToolbarColor(Color.Argb(255, 52, 152, 219))
               .SetShowTitle(true)
               .EnableUrlBarHiding();

            var customTabsIntent = builder.Build();

            // ensures the intent is not kept in the history stack, which makes
            // sure navigating away from it will close it
            customTabsIntent.Intent.AddFlags(ActivityFlags.NoHistory);

            Action<string> callback = null;
            callback = url =>
            {
                OidcCallbackActivity.Callbacks -= callback;

                task.SetResult(new BrowserResult()
                {
                    Response = url
                });
            };

            OidcCallbackActivity.Callbacks += callback;

            customTabsIntent.LaunchUrl(_context, Android.Net.Uri.Parse(options.StartUrl));

            return task.Task;
        }
    }
}

还需要编写Callback页面的代码，当认证通过后，跳转到这个页面进行处理，然后返回主页面：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;

namespace AndroidClient
{
    [Activity(Label = "OidcCallbackActivity")]
    [IntentFilter(new[] { Intent.ActionView },
        Categories = new[] { Intent.CategoryDefault, Intent.CategoryBrowsable },
        DataScheme = "io.identitymodel.native",
        DataHost = "callback")]
    public class OidcCallbackActivity : Activity
    {
        public static event Action<string> Callbacks;

        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);

            Finish();

            Callbacks?.Invoke(Intent.DataString);
        }
    }
}