使用 Xamarin 和 SQL Server 创建带有按钮的列表视图

Question

我创建了一个项目，我在其中从数据库中检索数据并将其显示到ListView 中。见下图。

这是为ListView检索数据的代码

public class MainActivity : Activity
{
  public static  Context context;
    public static List<UserInfo> UserInfoList = new List<UserInfo>();

    public static ListView ListView;
    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);
        SetContentView (Resource.Layout.Main); 
        ListView = FindViewById<ListView>(Resource.Id.Listview);

        GetList list = new GetList();
        list.Execute();
    }
    public class GetList : AsyncTask
    { 
        Context con;
        protected override Java.Lang.Object DoInBackground(params Java.Lang.Object[] @params)
        {
            System.Net.Http.HttpClient client = new System.Net.Http.HttpClient( );

            var _WebApiUrl =  string.Format("URL");
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
            HttpResponseMessage messge = client.GetAsync(_WebApiUrl).Result;
            var Return_EventList = messge.Content.ReadAsStringAsync().Result;
            var EventList = JsonConvert.DeserializeObject<List<UserInfo>>(Return_EventList);

            foreach (var data in EventList)
            {
                UserInfoList.Add(data);
            }
            return true;
        }
        protected override void OnPreExecute()
        {
            base.OnPreExecute();

        }
        protected override void OnPostExecute(Java.Lang.Object result)
        {
            base.OnPostExecute(result);
            ListView.Adapter = new UserInfoListAdapter(context, UserInfoList);
        }

    }


    class UserInfoListAdapter : BaseAdapter<UserInfo>
    {
        private List<UserInfo> mItem = new List<UserInfo>();
        private Context context;
        public UserInfoListAdapter(Context mcontext, List<UserInfo> mItems)
        {
            mItem.Clear();
            mItem = mItems;
            context = mcontext;
            this.NotifyDataSetChanged();

        }
        public override UserInfo this[int position]
        {
            get
            {
                return mItem[position];
            }
        }

        public override int Count
        {
            get
            {
                return mItem.Count;
            }
        }

        public Context MContext { get; private set; }

        public override long GetItemId(int position)
        {
            return position;
        }

        public override View GetView(int position, View convertView, ViewGroup parent)
        { 
            View listitem = convertView; 
            listitem = LayoutInflater.From(parent.Context).Inflate(Resource.Layout.ListViewDesign, parent, false);
            TextView TxtName = listitem.FindViewById<TextView>(Resource.Id.TxtName);
            TextView TxtNumber = listitem.FindViewById<TextView>(Resource.Id.TxtNumber);
            TxtName.Text = mItem[position].firstname;
            TxtNumber.Text = mItem[position].contact_no;
            listitem.Click += (object sender, EventArgs e) =>
            {
                Toast.MakeText(parent.Context, "Clicked " + mItem[position].firstname, ToastLength.Long).Show();
            };

            return listitem;
        }
    }

}

我想在ListView 中放置按钮，每行一个。这是我想如何实现它的示例

现在，当用户单击按钮时，应根据数据库中的当前 ID 下载 pdf 文件。例如在我的数据库xray id 是1，所以当用户下载xray 的pdf 时，它应该基于1 的id 下载

Answer 1

• 将 TableLayout 放置在您的“ListViewDesign”android 布局中，以便 获得所需的视图（或者它可以通过设置线性布局来实现 它的方向水平和它的 layout_weight)
• 在第四列放置按钮
• 从 GetView 方法中移除点击事件

• GetView 方法中的访问按钮

  Button DownloadButton = view.FindViewbyId<Button>(Resource.Id.btn_download);
  DownloadButton.Click += delegate { DownloadFile( link + mItem[position].Id ) };
  

• 添加命名空间

  using System.Net;
  using System.IO;
  using System.Text;
  

• 在您的 listView 适配器类中添加一个新方法

  private void DownloadFile(string url)
  {
     var webClient = new WebClient();
     webClient.DownloadStringCompleted += (s, e) => {
     var text = e.Result; // get the downloaded text
     string documentsPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
     string localFilename = "downloaded.txt";
     string localPath = Path.Combine(documentsPath, localFilename);
     File.WriteAllText(localPath, text); // writes to local storage
  };
  var url = new Uri("http://xamarin.com");
  webClient.Encoding = Encoding.UTF8;
  webClient.DownloadStringAsync(url);
  RunOnUiThread(() => {
      Toast.MakeText(this, "Download Completed", ToastLength.Short).Show();
  });
  }