使用 HTTP 请求获取数据 Android Xamarin C#

Question

朋友们好，这是我的第一个 Android 应用程序，我正在尝试从 wep api 获取数据并显示在列表视图中。现在我先说说我的步骤，我做了 class 并且这个 class 通过 http 请求获取数据。

class WebRequests
{
    public static List<Item> GetAllItems()
    {
        List<Item> lp = new List<Item>();
        HttpClient client = new HttpClient();
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        try
        {
            HttpResponseMessage response = client.GetAsync("https://MyUrlToApi/api/myitems").Result;
            if (response.IsSuccessStatusCode)
            {
                lp = JsonConvert.DeserializeObject<Item[]>(response.Content.ReadAsStringAsync().Result).ToList();
            }
        }
        catch
        {

        }
        return lp;
    }

我制作了一个具有项目属性的模型：

public class Item
{
    public string Id { get; set; }
    public string Content { get; set; }

}

我的主要 Activity 是：

[Activity(Label = "GetDataFromWebApiAndroid", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{
    ListView listView;
    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        // Set our view from the "main" layout resource
        SetContentView (Resource.Layout.Main);
        var result = WebRequests.GetAllItems();

        listView = FindViewById<ListView>(Resource.Id.listAll);
        listView.Adapter = new ArrayAdapter(this, Android.Resource.Layout.SimpleListItem1, result);
        listView.ChoiceMode = ChoiceMode.None;
    }
}

所以当我运行我的应用程序时，我的列表视图显示如下：

但我的数据是：

任何人都可以帮助我并解释我做错了什么。

Answer 1

我找到了解决方案，也许这会对新 Android 开发人员有所帮助。特别感谢 AndyRes 正确的方法。因此，为了正确显示数据，我应该创建自定义适配器来绑定数据。首先必须创建项目class，我称之为模型：

public class Item
{
    public string Id { get; set; }
    public string Content { get; set; }

    public Item(string Id, string Content)
    {
        this.Id = Id;
        this.Content = Content;
    }
}

现在自定义适配器：

class ItemListAdapter : BaseAdapter<Item>
{
    Activity context;
    public List<Item> listItems { get; set; }
    public ItemListAdapter(Activity context, List<Item> Items) : base()
    {
        this.context = context;
        this.listItems = Items;
    }
    public override Item this[int position]
    {
        get
        {
            return this.listItems[position];
        }
    }

    public override int Count
    {
        get
        {
            return this.listItems.Count;
        }
    }

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

    public override View GetView(int position, View convertView, ViewGroup parent)
    {
        Item item = listItems[position];
        View view = convertView;
        if (convertView == null || !(convertView is LinearLayout))

            view = context.LayoutInflater.Inflate(Resource.Layout.Itemlayout, parent, false);
        TextView itemId = view.FindViewById(Resource.Id.textItemId) as TextView;
        TextView itemContent = view.FindViewById(Resource.Id.textItemContent) as TextView;

        itemId.SetText(item.Id, TextView.BufferType.Normal);
        itemContent.SetText(item.Content, TextView.BufferType.Normal);

        return view;

    }
}

最后在 Activity 中进行更改：

[Activity(Label = "CustomAdapterAndroidApp", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{
    private ListView listItems;
    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        // Set our view from the "main" layout resource
        SetContentView (Resource.Layout.Main);
        listItems = FindViewById<ListView>(Resource.Id.listViewItems);
        PopulateItemsList();
    }

    private void PopulateItemsList()
    {
        listItems.Adapter = new ItemListAdapter(
           this, new List<Item>
            {
                new Item("222", "First Sample"),
                new Item("111", "Второй пример"),
                new Item("333", "მესამე მანალითი")
            }); 

    }

不要忘记创建特殊布局来显示每个项目：

<?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="match_parent"
  android:layout_height="match_parent">
<TextView
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/textItemId" />
<TextView   
    android:textAppearance="?android:attr/textAppearanceSmall"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/textItemContent" />
</LinearLayout>

并确保主布局中的位置列表。再次感谢。

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