Question

我一直在寻找Xamarin搜索recyclerView的方式。有谁可以请我参加一个关于如何以Xamarin方式做到这一点的演示？

Answer 1

我写了一个关于如何实现此功能的简单演示，效果如this。您可以在此GitHub Repository中看到它。

有关详细信息，您可以阅读文档：Xamarin.Android中的Filtering ListView with SearchView和Xaver Kapeller's answer关于使用RecyclerView过滤SearchView。

感谢Xaver Kapeller的回答，他关于搜索RecyclerView的回答很棒，所以我决定将其翻译成Xamarin以帮助更多人。

设置SearchView

在文件夹res/menu中创建一个名为main.xml的新文件。在其中添加一个项目并将actionViewClass设置为android.support.v7.widget.SearchView。由于您使用的是支持库，因此必须使用支持库的命名空间来设置actionViewClass属性。您的xml文件应如下所示：

 <?xml version="1.0" encoding="utf-8"?>
 <menu xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto">
     <item android:id="@+id/action_search"
           android:title="Search"
           android:icon="@android:drawable/ic_menu_search"
           app:showAsAction="always|collapseActionView"
           app:actionViewClass="android.support.v7.widget.SearchView" />
  </menu>

在您的Activity中，您必须像往常一样对此菜单xml进行充气，然后您可以查找包含MenuItem的{{1}}并在SearchView上添加一个代理我们将用于监听对QueryTextChange：

SearchView

设置public override bool OnCreateOptionsMenu(IMenu menu) { MenuInflater.Inflate(Resource.Menu.main, menu); var item = menu.FindItem(Resource.Id.action_search); var searchView = MenuItemCompat.GetActionView(item); _searchView = searchView.JavaCast<Android.Support.V7.Widget.SearchView>(); _searchView.QueryTextChange += (s, e) => _adapter.Filter.InvokeFilter(e.NewText); _searchView.QueryTextSubmit += (s, e) => { // Handle enter/search button on keyboard here Toast.MakeText(this, "Searched for: " + e.Query, ToastLength.Short).Show(); e.Handled = true; }; MenuItemCompat.SetOnActionExpandListener(item, new SearchViewExpandListener(_adapter)); return true; } private class SearchViewExpandListener : Java.Lang.Object, MenuItemCompat.IOnActionExpandListener { private readonly IFilterable _adapter; public SearchViewExpandListener(IFilterable adapter) { _adapter = adapter; } public bool OnMenuItemActionCollapse(IMenuItem item) { _adapter.Filter.InvokeFilter(""); return true; } public bool OnMenuItemActionExpand(IMenuItem item) { return true; } }

首先，添加将用于此示例的模型类：

Adapter

这只是您的基本模型，它将在public class Chemical { public string Name { get; set; } public int DrawableId { get; set; } }中显示文字。这是显示布局的布局：

RecyclerView

这是<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:padding="5dp"> <ImageView android:id="@+id/chemImage" android:layout_width="50dp" android:layout_height="50dp" android:layout_alignParentLeft="true" android:layout_margin="5dp" /> <TextView android:id="@+id/chemName" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_toRightOf="@+id/chemImage" android:layout_centerInParent="true" android:layout_marginLeft="5dp" android:layout_marginRight="5dp" /> </RelativeLayout>类的ViewHolder：

ChemicalHolder

3。实施public class ChemicalHolder : RecyclerView.ViewHolder { public ImageView Image { get; private set; } public TextView Caption { get; private set; } public ChemicalHolder(View itemView) : base(itemView) { Image = itemView.FindViewById<ImageView>(Resource.Id.chemImage); Caption = itemView.FindViewById<TextView>(Resource.Id.chemName); } }

RecyclerView.Adapter

实施过滤逻辑

public class RecyclerViewAdapter : RecyclerView.Adapter, IFilterable
{
    private List<Chemical> _originalData;
    private List<Chemical> _items;
    private readonly Activity _context;

    public Filter Filter { get; private set; }

    public RecyclerViewAdapter(Activity activity, IEnumerable<Chemical> chemicals)
    {
        _items = chemicals.OrderBy(s => s.Name).ToList();
        _context = activity;

        Filter = new ChemicalFilter(this);
    }

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


    public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)
    {
        View itemView = LayoutInflater.From(parent.Context).Inflate(Resource.Layout.Chemical, parent, false);
        ChemicalHolder vh = new ChemicalHolder(itemView);
        return vh;
    }

    public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)
    {
        ChemicalHolder vh = holder as ChemicalHolder;

        var chemical = _items[position];

        vh.Image.SetImageResource(chemical.DrawableId);
        vh.Caption.Text = chemical.Name;
    }

    public override int ItemCount
    {
        get { return _items.Count; }
    }

    public class ChemicalHolder{...

    private class ChemicalFilter{//Implement the Filter logic
 }

使用它来实现此功能

private class ChemicalFilter : Filter
{
    private readonly RecyclerViewAdapter _adapter;
    public ChemicalFilter(RecyclerViewAdapter adapter)
    {
        _adapter = adapter;
    }

    protected override FilterResults PerformFiltering(ICharSequence constraint)
    {
        var returnObj = new FilterResults();
        var results = new List<Chemical>();
        if (_adapter._originalData == null)
            _adapter._originalData = _adapter._items;

        if (constraint == null) return returnObj;

        if (_adapter._originalData != null && _adapter._originalData.Any())
        {
            // Compare constraint to all names lowercased. 
            // It they are contained they are added to results.
            results.AddRange(
                _adapter._originalData.Where(
                    chemical => chemical.Name.ToLower().Contains(constraint.ToString())));
        }

        // Nasty piece of .NET to Java wrapping, be careful with this!
        returnObj.Values = FromArray(results.Select(r => r.ToJavaObject()).ToArray());
        returnObj.Count = results.Count;

        constraint.Dispose();

        return returnObj;
    }

    protected override void PublishResults(ICharSequence constraint, FilterResults results)
    {
        using (var values = results.Values)
            _adapter._items = values.ToArray<Java.Lang.Object>()
                .Select(r => r.ToNetObject<Chemical>()).ToList();

        _adapter.NotifyDataSetChanged();

        // Don't do this and see GREF counts rising
        constraint.Dispose();
        results.Dispose();
    }
}

通过RecyclerView搜索 - Xamarin.Droid

1 个答案: