大叔也说Xamarin~Android篇~调用远程API接口，发POST请求

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Xamarin我们在上节已经教大家如何去部署它的环境了，今天来说一个实际的例子，使用android客户调用.net web api的一个接口，并发送POST请求，当服务端回到请求后做出响应，客户端android将响应的内容输出，并跳换到别一个Activity页面，在新视图上加载网页内容到webView控件上，整个流程结束！

一在主页面上添加几个表单元素，账号，密码，登陆按钮，并在Activity类的OnCreate方法中为它们赋值，并添加按钮的click事件

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

            // Set our view from the "main" layout resource
            SetContentView (Resource.Layout.Main);
          
            // Get our button from the layout resource,
            // and attach an event to it
            Button button = FindViewById<Button> (Resource.Id.myButton);
            
            button.Click += delegate {
                button.Text = string.Format ("{0} clicks!", count++);
            };
            Android.Util.Log.Info ("normal", "日志zzl");
            var loginBtn = FindViewById<Button> (Resource.Id.loginBtn);
            var username = FindViewById<TextView> (Resource.Id.username);
            var password = FindViewById<TextView> (Resource.Id.password);
            var result = FindViewById<TextView> (Resource.Id.result);
            loginBtn.Click += delegate {

                string url = "http://api.xuexiba.com/v1/User/Login";
                //创建HttpClient（注意传入HttpClientHandler）
                using (var http = new HttpClient ()) {
                    var content = new FormUrlEncodedContent (new Dictionary<string, string> () { 
                        { "username",username.Text },
                        { "password",password.Text }
                        
                    });

                    var response = http.PostAsync (url, content);
                    result.Text = response.Result.Content.ReadAsStringAsync ().Result;
                 Intent intent = new Intent(this, typeof(ViewPageActivity));
                 StartActivity(intent);
 
                }
            };
        }

二在ViewPageActivity里添加一个webView用来显示网页的内容，如下代码

    protected override void OnCreate (Bundle savedInstanceState)
        {
            base.OnCreate (savedInstanceState);
            SetContentView (Resource.Layout.ViewPage);
            var webView = FindViewById<WebView> (Resource.Id.webView);
            //启用Javascript Enable
            webView.Settings.JavaScriptEnabled = true;
            //载入网址
            webView.LoadUrl ("http://www.sina.com");
            //直接在当前webView上打开
             webView.SetWebViewClient (new CustWebViewClient ());

        }

注意，代码webView.SetWebViewClient (new CustWebViewClient ())表示使用现有的webView加载网页内容，而如果不加这行，那么网页将使用系统自带的浏览器进行加载，

下载看一下CustWebViewClient 这个类的内容

public class CustWebViewClient : WebViewClient
    {
        public override bool ShouldOverrideUrlLoading (WebView view, string url)
        {
            view.LoadUrl (url);
            return true;
        }

    }