vs xamarin android 读取rest

private void Btn_Click(object sender, EventArgs e)
{
    var u = FindViewById<EditText>(Resource.Id.editText1).Text;
    var p = FindViewById<EditText>(Resource.Id.editText2).Text;
    var progressDialog = ProgressDialog.Show(this, "Please wait...", "Checking account info...", true);
    var t=new Thread(new ThreadStart(delegate
    {
        var r = Api.CheckUser(u, p);
        if (r.HasValue)
        {
            RunOnUiThread(() => progressDialog.Hide());
            AppConfig.Config.SetNowUserId(r.Value);
            StartActivity(typeof(MainActivity));
            Finish();
        }
        else
        {
            RunOnUiThread(() => Toast.MakeText(this, "用户名或密码错误", ToastLength.Long).Show());
            RunOnUiThread(() => progressDialog.Hide());
        }
                
    }));
    t.Start();
}

把loading框显示出来，然后开新线程做事，之后关闭loading框。

因为是开新线程，所以如果希望更新界面，需要使用 RunOnUiThread方法

还有另外的方式

private readonly TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();

private void Btn_Click(object sender, EventArgs e)
{
    var u = FindViewById<EditText>(Resource.Id.editText1).Text;
    var p = FindViewById<EditText>(Resource.Id.editText2).Text;
    var progressDialog = ProgressDialog.Show(this, "Please wait...", "Checking account info...", true);
    Task.Factory.StartNew(() =>
    {
        return Api.CheckUser(u, p);
    }).ContinueWith(r =>
    {
        progressDialog.Hide();
        if (r.Result.HasValue)
        {
            AppConfig.Config.SetNowUserId(r.Result.Value);
            StartActivity(typeof(MainActivity));
            Finish();
        }
        else
        {
            Toast.MakeText(this, "用户名或密码错误", ToastLength.Long).Show();
        }
                
    }, uiScheduler);
}

使用Task的ContinueWith，可以指定在ui上执行

访问网络需要给permission，在项目属性里，Android Manifest 下面列出了所有的permission，打钩internet