Question

我在Xamarin表单ListView

中遇到数据绑定问题

我有一个类来保存要绑定的数据，在运行时我会看到对象中的数据。
我创建了一个ObservableCollection，我将循环中的对象添加到其中，在运行时我看到对象并且数据在此对象中
我将ItemSource添加到列表和ItemTemplate中。
将项目添加到listView，但在运行时，Label名称为null。

这是页面代码：

using System;
using System.Collections.Generic;
using Punteam.GetTraderStatusApi;
using Punteam.ReceiveTraderStatusApi;
using Xamarin.Forms;
using System.Threading;
using System.Threading.Tasks;
using Newtonsoft.Json.Schema;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;
using Newtonsoft.Json.Linq;
using XLabs.Forms.Controls;
using System.Collections;
using System.Collections.ObjectModel;
using Punteam.RequestChatMessages;
using Punteam.ReceiveChatMessages;
using System.Diagnostics;

namespace Punteam
{

public partial class ChatForm : ContentPage
{
    ObservableCollection <chatDataSource> source;
    StatusAPI getStatus;
    bool KeyboardStatus = false;


    public ChatForm ()
    {
        InitializeComponent ();
        if (Device.OS == TargetPlatform.iOS) {
            txtMsg.HeightRequest = 34;
            btnTxt.HeightRequest = 34;
            btnPick.HeightRequest = 60;
        }


        double bottomOffset;
        Int32 i = 0;
        getStatus = new StatusAPI ();
        getStatus.json.memberList [0].memberId = App.memberId;
        getStatus.json.pType = Constants.pTypeTraderStatus;
        SendRequest (getStatus, Constants.pTypeTraderStatus, this);


        btnTxt.Clicked += (object sender, EventArgs e) => {
            i++;
            System.Diagnostics.Debug.WriteLine ("In button Clicked: " +   i.ToString ());
            if (Device.OS == TargetPlatform.Android) {
                btnPick.IsVisible = true;
            }
            txtMsg.Text = "";
        };


        KeyboardHelper.KeyboardChanged += (sender, e) => {
            if (KeyboardStatus) {
            } else {
            }
            bottomOffset = mainStack.Bounds.Bottom -     textStack.Bounds.Bottom;   // This offset allows us to only raise the     stack by the amount required to stay above the keyboard. 
                textStack.TranslationY -= e.Visible ? e.Height -       bottomOffset : bottomOffset - e.Height;  // The textStack is translated up,  and then returned to original position.
        };
    }


    public  static async Task<string> SendRequest (Object obj, String    pType, ChatForm chat)
    {
        // Get Trader status    
        String jsonSring = "";
        Utils util = new Utils ();
        jsonSring = util.deserialze (obj);
        var result = await Http.SendData (Constants.serverAddress, jsonSring, true);
        string inputStr = (string)result;
        Punteam.ReceiveTraderStatusApi.RootObject traderStatus = new    Punteam.ReceiveTraderStatusApi.RootObject ();
        traderStatus =  JsonConvert.DeserializeObject<Punteam.ReceiveTraderStatusApi.RootObject>   (inputStr);

        // Get Chat last messages
        ChatdAPI chatApi = new ChatdAPI ();
        chatApi.json.pType = Constants.puTypeGetChatMessages; 
        chatApi.json.memberList [0].memberId = App.memberId;
        jsonSring = "";
        jsonSring = util.deserialze (chatApi);
        result = await Http.SendData (Constants.serverAddress, jsonSring, true);
        Punteam.ReceiveChatMessages.ReceivedMemberMessages memberMessages = new Punteam.ReceiveChatMessages.ReceivedMemberMessages ();
        memberMessages = JsonConvert.DeserializeObject<Punteam.ReceiveChatMessages.ReceivedMemberMessages> (result);

        chat.fillChatList (memberMessages);
        return result;
    }

    public void fillChatList   (Punteam.ReceiveChatMessages.ReceivedMemberMessages memberMessages)
    {
        var chatLine = new chatDataSource ();
        source = new ObservableCollection<chatDataSource> ();
        Int32 chatIndex = memberMessages.MemberChatMessagesData.Count;
        for (int i = 0; i < chatIndex; i++) {
            chatLine = new chatDataSource ();
            chatLine.senderName = memberMessages.MemberChatMessagesData [i].SenderName;
            chatLine.text = memberMessages.MemberChatMessagesData [i].Message;
            source.Add (chatLine);
        }

        chatList.ItemsSource = source;

        chatList.ItemTemplate = new DataTemplate (() => {


            var name = new Label ();

            return new ViewCell{ View = name };
        });
    }

    public void txtMsgFocused (Object s, EventArgs a)
    {
        if (Device.OS == TargetPlatform.Android) {
            btnPick.IsVisible = false;
        }
    }

    public void txtMsgCompleted (Object s, EventArgs a)
    {
        if (Device.OS == TargetPlatform.Android) {
            btnPick.IsVisible = true;
        }

    }
    *
    public void sendClicked (Object s, EventArgs a)
    {
        if (Device.OS == TargetPlatform.Android) {
            btnPick.IsVisible = true;
        }

    }

    public void itemTapped (Object s, EventArgs a)
    {
        if (Device.OS == TargetPlatform.Android) {
            btnPick.IsVisible = true;
        }
    }


}

public class chatDataSource
{
    public string senderName = "";
    public string text = "";
}
}

Answer 1

发现问题：数据源类看起来像这样

public class chatDataSource
{
    public string senderName = "";
    public string text = "";
}

它应该有它的字段是这样的属性：

    public class chatDataSource
{

    public string senderName { get; set; }

    public string text { get; set; }
}

Answer 2

在ListView中，您必须将视图绑定到模型类属性。

在您的情况下，模型类“chatDataSource”具有senderName和text。

因此，xaml中的绑定应如下所示：

<Label x:Name="labelname" Text="{Binding senderName}" />

或Text =“{Binding text}”

请确保Binding属性中的名称和Model类中属性的名称完全相同。

Xamarin表单ListView绑定问题

2 个答案: