如何使用REST API，自定義列表視圖，適配器，行布局在Xamarin Android C＃中填充列表視圖

Question

我一般的編程知識非常有限。 嘗試創建自定義列表視圖以主要顯示圖像和消息。

我一直在嘗試遵循有關如何做的教程，但終生無法解決如何使其工作..

當前有這些錯誤，不知道如何解決：

[！[msgInbox屏幕錯誤] [1]] [1]

這是帶有列表的msgInbox活動：

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

using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Dribl;
using Newtonsoft.Json;

namespace Dribl.Droid
{
    [Activity(Label = "MsgInbox", Theme = "@style/CustomActionBarTheme")]
    public class MsgInbox : Activity
    {

        TextView txt;

        //Button backBtn;

        private List<Message> msgItems;

        private ListView msgListview;

        //private BaseAdapter<msgInfo> mAdapter;

        //action bar layout buttons
        LinearLayout surveysBtn;


        LinearLayout availabilityBtn;


        LinearLayout inboxBtn;


        LinearLayout dashboardBtn;




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

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.msgInbox);
            //add the action bar to the layout 
            ActionBar.SetCustomView(Resource.Layout.action_bar);
            ActionBar.SetDisplayShowCustomEnabled(true);



            //actionbar layout btns
            //actionbar layout btns
            surveysBtn = FindViewById<LinearLayout>(Resource.Id.SurveyLayout);
            surveysBtn.Click += surveyBtn_Click;

            inboxBtn = FindViewById<LinearLayout>(Resource.Id.InboxLayout);
            inboxBtn.Click += InboxBtn_Click;


            availabilityBtn = FindViewById<LinearLayout>(Resource.Id.availabilityLayout);
            availabilityBtn.Click += availabilityBtn_Click;

            dashboardBtn = FindViewById<LinearLayout>(Resource.Id.dashboardLayout);
            dashboardBtn.Click += dashboardBtn_Click;


            txt = FindViewById<TextView>(Resource.Id.msg_txt);


            WebClient client = new WebClient();
            System.Uri uri = new System.Uri("http://dribl.com/api/getAllMyMessages");
            NameValueCollection parameters = new NameValueCollection();


            parameters.Add("token", GlobalVariables.token);

            client.UploadValuesAsync(uri, parameters);
            client.UploadValuesCompleted += client_UploadValuesCompleted;

            //listview
            msgListview = FindViewById<ListView>(Resource.Id.msgListView);
            msgListview.ItemClick += MsgListview_ItemClick;


        }

        private void MsgListview_ItemClick(object sender, AdapterView.ItemClickEventArgs e)
        {
            Intent intent = new Intent(this, typeof(msgDetails));

            //add in a variable to store the message that was clicked on and pass across to next pages txtfield
            intent.PutExtra("msgDet", "This is a message");
            StartActivity(intent);
        }

        protected internal void client_UploadValuesCompleted(object sender, UploadValuesCompletedEventArgs e)
        {
            string json = Encoding.UTF8.GetString(e.Result);
            List<Message> messages = JsonConvert.DeserializeObject<List<Message>>(json);

            //display the retrieved msg in the console output
            //Console.WriteLine(message[1].message + " is the message");

            //display the msg in a text view at top of page
            //txt.Text = message[1].message;


            //get the list view create a string to store and add to the list view based on the json return

            // msgItems = new List<Message>();

            // for (int c = 0; c < message.Count; c++)
            // {

            //     msgItems.Add(message[c].message);
            //msgItems.Add(new Message() { message = "pauls hectic"});
            //}

            msgItems = messages;

           // msgAdapter msgAdapter = new msgAdapter(this, msgItems);
            //msgListview.Adapter = msgAdapter;


            //Msgs.Add(message[1].message);
            //Msgs.Add(message[0].message);

           // ArrayAdapter<Message> adapter = new ArrayAdapter<Message>(this, Android.Resource.Layout.SimpleListItem1, msgItems);
            //msgListview.Adapter = adapter;
           // msgAdapter msgAdapter = new MsgAdapter(this, message);
            //var msgAdapter = new MsgAdapter(this, message);
            MsgAdapter msgAdapter = new MsgAdapter(this, messages);
        }


        void surveyBtn_Click(object sender, EventArgs e)
        {
            Intent intent = new Intent(this, typeof(Surveys));
            this.StartActivity(intent);
            this.Finish();
        }

        void dashboardBtn_Click(object sender, EventArgs e)
        {
            Intent intent = new Intent(this, typeof(dashboard));
            this.StartActivity(intent);
            this.Finish();
        }

        void availabilityBtn_Click(object sender, EventArgs e)
        {
            Intent intent = new Intent(this, typeof(Availability));
            this.StartActivity(intent);
            this.Finish();
        }

        void InboxBtn_Click(object sender, EventArgs e)
        {
            Intent intent = new Intent(this, typeof(MsgInbox));
            this.StartActivity(intent);
            this.Finish();
        }





    }


}

這是msgInfo類：

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 Dribl.Droid
{

            public class Message
        {

            public string messages { get; set; }


    }

}

這是味精適配器：

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 Dribl.Droid
{


    class MsgAdapter : BaseAdapter<Message>
    {
        private List<Message> msgItems;
        private Context msgContext;

        public MsgAdapter(Context Context, List<Message> Items)
        {
            msgItems = Items;
            msgContext = Context;
        }
        public override int Count
        {
            get { return msgItems.Count; }
        }
        public override long GetItemId(int position)
        {
            return position;
        }
        public override Message this[int position]
        {
            get { return msgItems[position]; }
        }
        public override View GetView(int position, View convertView, ViewGroup parent)
        {
            View row = convertView;

            if (row == null)
            {
                row = LayoutInflater.From(msgContext).Inflate(Resource.Layout.msgCell, parent, false);
            }


            TextView message = row.FindViewById<TextView>(Resource.Id.message);
            message.Text = msgItems[position].messages;

            return row;
        }
    }
}

Answer 1

List<Message> message = JsonConvert.DeserializeObject<List<Message>>(json);

message已經是消息List<Message>因此您無需創建新消息。 只需將此對象傳遞給適配器構造函數即可。

您可以刪除此部分：

       msgItems = new List<Message>();

        for (int c = 0; c < message.Count; c++)
        {
            msgItems.Add(message[c].message);
        }

但是，如果您想保留消息列表，則只需要：

msgItems = messages;

然后創建您的適配器對象：

msgAdapter adapter = new msgAdapter(this, message);

或者你也可以

var adapter = new msgAdapter(this, message);

並添加適配器：

msgListview.Adapter = adapter;

筆記：

將message變量更改為messages，因為它包含多個消息。

msgAdapter將該名稱更改為MsgAdapter （大寫的第一個字母），這樣您就不會發現何時是類以及何時是對象的問題。

更新：

您的適配器的GetView方法中有一個錯誤。

擴大行時，您需要指出父項：

row = LayoutInflater.From(msgContext).Inflate(Resource.Layout.msgCell, parent, false);