通过 RecyclerView 搜索 - Xamarin.Droid

Question

我一直在寻找通过 recyclerView 搜索的 Xamarin 方式。任何人都可以向我介绍如何以 Xamarin 方式执行此操作的演示吗？

Answer 1

我写了一个关于如何实现这个功能的简单演示，效果类似于this。 你可以在这个GitHub Repository看到它。

有关更多信息，您可以阅读文档：Xamarin.Android 中的Filtering ListView with SearchView 和Xaver Kapeller's answer 关于过滤RecyclerView 和SearchView。

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

1. 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，因此您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，您必须像往常一样扩充此菜单xml，然后您可以查找包含SearchView 的MenuItem 并在QueryTextChange 上添加一个委托，我们将使用它来监听更改输入到SearchView 中的文本：

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;
        }
    }

1. 设置Adapter

首先，添加一个将用于此示例的模型类：

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

    public int DrawableId { get; set; }
}

这只是您的基本模型，它将在RecyclerView 中显示文本。这是显示布局的布局：

<?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>

这是ChemicalHolder 类的ViewHolder：

    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);
        }
    }

3。 实现RecyclerView.Adapter

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
 }

4. 实现过滤逻辑

   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();
       }
   }
   

5. 用它来实现这个功能

       SetContentView(Resource.Layout.Main);
       SupportActionBar.SetDisplayShowHomeEnabled(true);
   
       var chemicals = new List<Chemical>
       {
           new Chemical {Name = "Niacin", DrawableId = Resource.Drawable.Icon},
           new Chemical {Name = "Biotin", DrawableId = Resource.Drawable.Icon},
           new Chemical {Name = "Chromichlorid", DrawableId = Resource.Drawable.Icon},
           new Chemical {Name = "Natriumselenit", DrawableId = Resource.Drawable.Icon},
           new Chemical {Name = "Manganosulfate", DrawableId = Resource.Drawable.Icon},
           new Chemical {Name = "Natriummolybdate", DrawableId = Resource.Drawable.Icon},
           new Chemical {Name = "Ergocalciferol", DrawableId = Resource.Drawable.Icon},
           new Chemical {Name = "Cyanocobalamin", DrawableId = Resource.Drawable.Icon},
       };
   
       _recyclerView = FindViewById<RecyclerView>(Resource.Id.recyclerView);
       _adapter = new RecyclerViewAdapter(this,chemicals);
       _LayoutManager = new LinearLayoutManager(this);
       _recyclerView.SetLayoutManager(_LayoutManager);
       _recyclerView.SetAdapter(_adapter);//