c# - Xamarin 自定义多选 ListView

Question

我想知道是否有办法制作一个多选 ListView ，它实际上能够返回选定的索引。我已经能够使用预制的 multiplechoicelistview 适配器来完成它，但我需要能够编辑它的样式。所以我需要一个自定义 ListView 。这是我的oncreate代码a

 protected override void OnCreate(Bundle savedInstanceState)
    {

        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.Options);
        outList = FindViewById<ListView>(Resource.Id.outList);
        var btnCheck = FindViewById<ImageButton>(Resource.Id.btnConfirm);
        var btnBack = FindViewById<ImageButton>(Resource.Id.btnBack);
        for (int i = 0; i < NewProfileVars.LifeStyles.Length; i++)
        {
            inList.Add(NewProfileVars.LifeStyles[i].Name);
        }


        //list contents end here

        ListViewAdapter adapter = new ListViewAdapter(this, inList);
        outList.Adapter = adapter;
        outList.ChoiceMode = ChoiceMode.Multiple;
        NewProfile main = new NewProfile();
        btnCheck.Click += Confirm;
        btnBack.Click += Back;


    }

这是我的 ListView 适配器代码

    class ListViewAdapter: BaseAdapter<string>
    {
        public List<string> Items;
        public Context Context;

        public ListViewAdapter(Context context, List<string> items)
        {
            Items = items;
            Context = context;
        }


        public override int Count
        {
            get { return Items.Count; }
        }

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

        }
        public override string this[int position]
        {
            get { return Items[position]; }
        }

        public override View GetView(int position, View convertView, ViewGroup parent)
        {
            View row = convertView;

            if (row == null)
            {
                row = LayoutInflater.From(Context).Inflate(Resource.Layout.ListBox, null, false);

            }
            CheckBox txtName = row.FindViewById<CheckBox>(Resource.Id.cbName);
            txtName.Text = Items[position];
            return row;
        }
    }

我现在需要的是弄清楚确认按钮将如何保存我选择的内容。提前感谢您的帮助。

Answer 1

我看到您在 ListView 中使用了 CheckBox。您可以使用类似这样的方式获取 Checked 的项目:

首先创建一个类来保存您的项目数据和 Checked 状态，我们称其为示例

public class LifeStylesListItem
{
    public string Name { get; set; }

    public bool IsSelected { get; set; }

    public LifeStylesListItem(string name)
    {
        Name = name;
    }
}

然后修改你的ListViewAdapter

添加一个新的私有(private)字段，用于保存 LifeStylesListItem 列表

private List<LifeStylesListItem> _list;

使用构造函数中传递的 Items 初始化列表。

public ListViewAdapter(Context context, List<string> items)
{
    Items = items;
    _list = new List<LifeStylesListItem>();

    //Your are creating a copy of your Items
    foreach (var item in items)
    {
        _list.Add(new LifeStylesListItem(item));
    }

    Context = context;
}

在 GetView 方法中订阅 CheckBox 的 CheckedChange 事件。这样，当检查状态发生变化时，您会收到通知。您还需要根据 Item IsSelected 值设置 Checked 属性。当 ListView 将重用您的单元格时，这是必需的。

public override View GetView(int position, View convertView, ViewGroup parent)
{
    View row = convertView;

    if (row == null)
    {
        row = LayoutInflater.From(Context).Inflate(Resource.Layout.ListBox, null, false);

    }
    CheckBox txtName = row.FindViewById<CheckBox>(Resource.Id.cbName);
    txtName.Text = _list[position].Name;
    txtName.Checked = _list[position].IsSelected;

    txtName.CheckedChange -= TxtName_CheckedChange;
    txtName.CheckedChange += TxtName_CheckedChange;

    return row;
}

添加事件处理程序TxtName_CheckedChange 方法

void TxtName_CheckedChange(object sender, CompoundButton.CheckedChangeEventArgs e)
{
    //These lines are used to get the position of the control that was clicked
    var obj = sender as CheckBox;
    var row = obj?.Parent as View; 
    var parent = row?.Parent as ListView;

    if (parent == null)
    {
        return;
    }

    var position = parent.GetPositionForView(row);

    // Once you have the position you can get the item and change
    // its IsSelected
    var item = _list[position];
    item.IsSelected = e.IsChecked;
}

然后在适配器中添加的最后一个方法是返回所选项目的方法。借助 Linq(需要添加using System.Linq)，您可以像这样查询所选项目。

public List<string> GetCheckedItems()
{
    return _list
            .Where(a => a.IsSelected)
            .Select(b => b.Name)
            .ToList();
}

现在在您的 Activity 中，您只需在单击“确认”按钮时从 ListViewAdapter 方法调用 GetCheckedItems:

private void Confirm(object sender, EventArgs e)
{
    var checkedItems = adapter.GetCheckedItems();
}

请记住将 adapter 更改为 Activity 中的私有(private)字段

private ListViewAdapter adapter;

希望这有帮助。-