如何使用 REST API、自定义列表视图、适配器、行布局在 xamarin android c# 中填充列表视图

Question

我对编程的了解非常有限。尝试创建自定义列表视图以主要显示图像和消息。

我一直在尝试遵循有关如何执行此操作的教程，并且一生都无法弄清楚如何使其工作..

目前有这些错误，不知道如何解决：

[！msg收件箱屏幕错误

][1]][1]

这是包含列表的 msgInbox 活动：

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();
        }


    }

}

这是 msgInfo 类：

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; }

    }
}

这是味精适配器：

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);

消息

已经是List<Message>消息的列表，因此您无需创建新消息。只需将此对象传递给适配器构造函数即可。

您可以删除此部分：

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

但是，如果您想保存消息列表，则只需要：

msgItems = messages;

然后创建适配器对象：

msgAdapter adapter = new msgAdapter(this, message);

或者你也可以

var adapter = new msgAdapter(this, message);

并添加适配器：

msgListview.Adapter = adapter;

笔记：

将消息变量更改为消息，因为这包含多个消息。

msgAdapter 将名称更改为 MsgAdapter(大写的第一个字母(，这样您就不会在查找它何时是类以及何时是对象时遇到问题。

更新：

适配器的GetView方法有错误。

您需要在膨胀行时指明父级：

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