通过RecyclerView - Xamarin.Droid搜索

Question

我一直在寻找通过recyclerView搜索的Xamarin方法。有人能给我介绍一下如何用Xamarin的方法来做这个演示吗？

Answer 1

我编写了一个关于如何实现这个特性的简单演示，效果类似于这。您可以在这个GitHub仓库中看到它。

有关更多信息，您可以阅读文档：用ListView对SearchView进行滤波 in Xamarin.Android和Xaver Kapeller的回答 in a RecyclerView with SearchView。

谢谢Xaver Kapeller的回答，他关于通过RecyclerView搜索的回答很棒，所以我决定把它翻译成Xamarin，以帮助更多的人。

1. 设置SearchView的

在文件夹中，res/menu创建一个名为main.xml的新文件。在其中添加一个项并将actionViewClass设置为android.support.v7.widget.SearchView。由于使用的是支持库，所以必须使用支持库的命名空间来设置actionViewClass属性。xml文件应该如下所示：

 <?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，您必须像往常一样膨胀此菜单xml，然后您可以查找包含SearchView的MenuItem，并在QueryTextChange上添加一个委托，我们将使用该委托来侦听输入到SearchView的文本的更改。

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的

首先，添加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>

这是用于ViewHolder类的ChemicalHolder：

    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);
        }
    }

1. 实现RecyclerView.Adapter的

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
 }

1. 实现过滤逻辑 私有类ChemicalFilter :筛选器{私有只读RecyclerViewAdapter _adapter；公共ChemicalFilter(RecyclerViewAdapter适配器){ _adapter =适配器；}受保护的覆盖FilterResults PerformFiltering(ICharSequence约束){ var returnObj =新FilterResults()；var结果=新列表()；if (_adapter._originalData == null) _adapter._originalData = _adapter._items；if (约束==空)返回returnObj；if (_adapter._originalData != null && _adapter._originalData.Any()) { //比较约束到所有被小写的名称。//它们包含它们，它们被添加到结果中。results.AddRange( _adapter._originalData.Where(化学results.AddRange} //讨厌的.NET到Java包装)，小心这个！returnObj.Values = FromArray(results.Select(r => r.ToJavaObject()).ToArray()；returnObj.Count = results.Count；constraint.Dispose()；返回returnObj；}保护覆盖PublishResults(ICharSequence约束，FilterResults结果){ see (var值= results.Values) _adapter._items = values.ToArray() .Select(r => r.ToNetObject().ToList()；_adapter.NotifyDataSetChanged()；//不要这样做，查看GREF计数上升的constraint.Dispose()；results.Dispose()；}}
2. 使用它来实现这个特性 SupportActionBar.SetDisplayShowHomeEnabled(true)；；SetContentView(Resource.Layout.Main)DrawableId = Resource.Drawable.Icon}，新化学{Name = "Biotin"，DrawableId = Resource.Drawable.Icon}，新化学{Name = "Chromichlorid"，DrawableId = Resource.Drawable.Icon}，新化学{Name = "Natriumselenit"，DrawableId = Resource.Drawable.Icon}，新化学{Name =“Mangano硫酸盐”，DrawableId = Resource.Drawable.Icon}，新化学品{Name = "Natriummolybdate"，DrawableId = Resource.Drawable.Icon}，新化学{Name = "Ergocalciferol"，DrawableId = Resource.Drawable.Icon}，新化学{Name =“氰基钴胺”，DrawableId =Resource.Drawable.Icon }；_recyclerView = FindViewById(Resource.Id.recyclerView)；_adapter =新RecyclerViewAdapter(此为化学品)；_LayoutManager =新LinearLayoutManager(此)；RecyclerViewAdapter _recyclerView.SetAdapter(_adapter);//