我不明白为什么 ListView 中的选择消失了

Question

我想选择 ListView 中的一项，然后按编辑按钮，该按钮对选定的 Listview 项进行处理。但是只要我从列表视图中移动鼠标，选择就会消失。 （我在VS模拟器上测试） 我确实在 Internet 上查找了示例，但它们使用了根本不存在的不同属性。

这里是axml的部分代码：

    <TableLayout
        android:orientation="horizontal"
        android:minWidth="25px"
        android:minHeight="25px"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/linearLayout4">
        <TableRow>
            <TextView
                android:text="Ingredients List :"
                android:textAppearance="?android:attr/textAppearanceSmall"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:id="@+id/textView1" />
            <Button
                android:text="Edit"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:id="@+id/editIngerientsButton" />
        </TableRow>
        <TableRow>
            <ListView
                android:minWidth="25px"
                android:minHeight="50px"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/ingredientsListView"
                android:layout_span="2"
                android:choiceMode="singleChoice" />
        </TableRow>
    </TableLayout>

这里是代码

        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            SetContentView(Resource.Layout.parsing_recepie);

            ingredientsListView = (ListView) FindViewById(Resource.Id.ingredientsListView);
            ingredients = new List<Ingredient>();
            arrayAdapter = new ArrayAdapter<Ingredient>(this,
                Android.Resource.Layout.SimpleListItem1, ingredients);
            ingredientsListView.Adapter = arrayAdapter;
            ingredientsListView.ChoiceMode = ChoiceMode.Single;

            editIngredientsButton = (Button) FindViewById(Resource.Id.editIngerientsButton);
            editIngredientsButton.Click += EditIngredientsButtonOnClick;
     }

Answer 1

您应该为 ListView 自定义 Adapter。将 selectItem 属性添加到适配器中。选中项目后，更改项目单元格的状态。

ItemSelectedAdapter.cs：

public class ItemSelectedAdapter : BaseAdapter<string>
{
    string[] items;
    Activity context;
    public int selectItem = -1;

    public ItemSelectedAdapter(Activity context, string[] items) : base()
    {
        this.context = context;
        this.items = items;
    }
    public override long GetItemId(int position)
    {
        return position;
    }
    public override string this[int position]
    {
        get { return items[position]; }
    }
    public override int Count
    {
        get { return items.Length; }
    }
    public override View GetView(int position, View convertView, ViewGroup parent)
    {
        View view = convertView; // re-use an existing view, if one is available
        if (view == null) // otherwise create a new one
            view = context.LayoutInflater.Inflate(Android.Resource.Layout.SimpleListItem1, null);
        view.FindViewById<TextView>(Android.Resource.Id.Text1).Text = items[position];
        if (selectItem == position)
        {
            view.FindViewById<TextView>(Android.Resource.Id.Text1).SetBackgroundColor(Android.Graphics.Color.Yellow);
        }
        else
        {
            view.FindViewById<TextView>(Android.Resource.Id.Text1).SetBackgroundColor(Android.Graphics.Color.Transparent);
        }

        return view;
    }

    public void setSelectItem(int selectItem)
    {
        this.selectItem = selectItem;
    }
}

SimpleListItem1.xml：

<?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:id="@+id/Text1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

终于在Activity：

ListView listView;
string[] items;
ItemSelectedAdapter itemSelectedAdapter;
Button editButton;


listView = FindViewById<ListView>(Resource.Id.listView1);
items = new string[] { "Vegetables", "Fruits", "Flower Buds", "Legumes", "Bulbs", "Tubers" };
itemSelectedAdapter= new ItemSelectedAdapter(this, items);
listView.Adapter = itemSelectedAdapter;
listView.ItemClick += ListView_ItemClick;

editButton= FindViewById<Button>(Resource.Id.button2);
editButton.Click += Button2_Click;

private void ListView_ItemClick(object sender, AdapterView.ItemClickEventArgs e)
{
    itemSelectedAdapter.setSelectItem(e.Position);
    Console.WriteLine("selected is：" + e.Position);
    itemSelectedAdapter.NotifyDataSetChanged();
}

private void Button2_Click(object sender, EventArgs e)
{
    int selectItemID = (int)homeScreenAdapter.selectItem;
    Console.WriteLine("selected is：" + selectItemID);
    items[selectItemID] = atv_content.Text;
    homeScreenAdapter.NotifyDataSetChanged();
 }