Searchview.setOnQueryTextListener NullPointException

Question

这是MainActivity中的搜索视图

searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
        @Override
        public boolean onQueryTextSubmit(String text) {
            return false;
        }

        @Override
        public boolean onQueryTextChange(String text) {
            servantAdapter.getFilter().filter(text);
            //Toast.makeText(MainActivity.this,text,Toast.LENGTH_SHORT).show();
            return true;
        }
    });
}

这是适配器

public class ServantAdapter extends RecyclerView.Adapter<ServantAdapter.ViewHolder>implements Filterable {
private List<Servant> mServant;
 @Override
public Filter getFilter() {//The front omitted...
    return new Filter() {
        @SuppressWarnings("unchecked")
        @Override
        protected void publishResults(CharSequence constraint, FilterResults filterResults) {
            mServant = (List<Servant>) filterResults.values;
            ServantAdapter.this.notifyDataSetChanged();
        }
        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            List<Servant> filteredResults = null;
            if (constraint.length() == 0) {
                filteredResults = mServant;
            } else {
                filteredResults = getFilteredResults(constraint.toString().toLowerCase());
            }

            FilterResults results = new FilterResults();
            results.values = filteredResults;

            return results;
        }

    };
}
protected List<Servant> getFilteredResults(String constraint) {
    List<Servant> results = new ArrayList<>();

    for (Servant item : mServant) {
        if (item.getName().toLowerCase().contains(constraint)) {
            results.add(item);
        }
    }
    return results;
}

为什么当我运行此程序并在searchview中输入某些内容时，程序将被关闭并返回ReportErrors java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'android.widget.Filter com.example.a76959.tired.ServantAdapter.getFilter（）'

但是如果我在代码中使用Toast，程序可以定期运行并向我输入的消息干预（我没有在工具栏或ActionBar中使用searchview，我只将它放在MainActivity.xml中的recyclerview顶部，我不知道它是否有任何影响） 谁能帮助我...（感谢您阅读我可怜的英语Orz ..）

Answer 1

当您使用<?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:background="@drawable/artist_cell_background"> <ImageView android:id="@+id/imageView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_alignParentStart="true" android:layout_centerVertical="true" android:layout_margin="10dp" android:src="@drawable/ic_music_note_24dp"> </ImageView> <ImageButton android:id="@+id/artist_button" android:src="@drawable/ic_add_24dp" android:layout_width="100dp" android:layout_height="match_parent" android:layout_centerVertical="true" android:layout_alignParentRight="true" android:layout_alignParentEnd="true" android:background="@drawable/artist_cell_playlist_button_background"> </ImageButton> <TextView android:id="@+id/artist_name" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ellipsize="end" android:lines="1" android:textAppearance="?android:attr/textAppearanceMedium" android:textColor="@android:color/black" android:layout_alignParentTop="true" android:layout_marginTop="10dp" android:layout_toRightOf="@id/imageView" android:layout_toEndOf="@id/imageView" android:layout_toLeftOf="@id/artist_button" android:layout_toStartOf="@id/artist_button"> </TextView> <TextView android:id="@+id/number_of_albums" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ellipsize="end" android:lines="1" android:textAppearance="?android:attr/textAppearanceSmall" android:layout_marginBottom="10dp" android:layout_toRightOf="@id/imageView" android:layout_toEndOf="@id/imageView" android:layout_toLeftOf="@id/artist_button" android:layout_toStartOf="@id/artist_button" android:layout_below="@id/artist_name"> </TextView> </RelativeLayout> 时，请确保变量{ "error": { "message": "(#100) An owning business is required for this request", "type": "OAuthException", "code": 100, "fbtrace_id": "C1wGrChj+O3" } } 已正确实例化且不为空。

使用：

servantAdapter.getFilter().filter(text);

或者：

servantAdapter