使用searchview应用筛选器时，RecyclerView上的空白输出

Question

我正在学习一个教程，用SearchView在我的RecyclerView上实现一个过滤器。一旦我在搜索查询中键入内容，我的RecyclerView就会变为空白。几个小时以来，我一直在思考这个问题，我觉得离解决方案还差得很远。

这是我的适配器类

package com.example.internetconnectivityapplication;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Filter;
import android.widget.Filterable;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
public class DataAdapter extends RecyclerView.Adapter<DataAdapter.MyViewHolder> implements Filterable {
private List<Data> dataList;
private List<Data> dataListFull;
public class MyViewHolder extends RecyclerView.ViewHolder{
public TextView dataName;
public MyViewHolder(View view){
super(view);
dataName = (TextView) view.findViewById(R.id.data_name);
}
}
public DataAdapter(List<Data> dataList){
this.dataList = dataList;
this.dataListFull = new ArrayList<>(dataList);
}
@NonNull
@Override
public DataAdapter.MyViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
View viewItem = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.data_row,viewGroup,false);
return new MyViewHolder(viewItem);
}
@Override
public void onBindViewHolder(@NonNull DataAdapter.MyViewHolder myViewHolder, int i) {
Data data = dataList.get(i);
myViewHolder.dataName.setText(data.getDataString());
}
@Override
public int getItemCount() {
return dataList.size();
}
@Override
public Filter getFilter() {
return dataFilter;
}
private Filter dataFilter = new Filter() {
@Override
protected FilterResults performFiltering(CharSequence constraint) {
List<Data> filteredDataList = new ArrayList<>();
if(constraint == null || constraint.length() == 0){
filteredDataList.addAll(dataListFull);
} else {
String filterParameter = constraint.toString().toLowerCase().trim();
for(Data data : dataListFull){
if(data.getDataString().toLowerCase().trim().contains(filterParameter)){
filteredDataList.add(data);
}
}
}
FilterResults filterResults = new FilterResults();
filterResults.values = filteredDataList;
return filterResults;
}
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
dataList.clear();
dataList.addAll((List) results.values);
notifyDataSetChanged();
}
};
}

这里是模型类

package com.example.internetconnectivityapplication;

public class Data {
String dataString;
public Data(String dataString){
this.dataString = dataString;
}
public String getDataString(){
return dataString;
}
}

这里是主活动类

package com.example.internetconnectivityapplication;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.SearchView;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import org.apache.commons.io.IOUtils;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import javax.net.ssl.HttpsURLConnection;
public class MainActivity extends AppCompatActivity {
private List<Data> dataList = new ArrayList<>();
private RecyclerView recyclerView;
private DataAdapter dataAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
dataAdapter = new DataAdapter(dataList);
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getApplicationContext());
recyclerView.setLayoutManager(layoutManager);
recyclerView.setItemAnimator(new DefaultItemAnimator());
recyclerView.setAdapter(dataAdapter);
new GetData().execute();
}
private class GetData extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... voids) {
try {
// Create URL
URL githubEndpoint = new URL("https://api.github.com/");
// Create connection
HttpsURLConnection myConnection =
(HttpsURLConnection) githubEndpoint.openConnection();
myConnection.setRequestProperty("User-Agent", "my-rest-app-v0.1");
myConnection.setRequestMethod("GET");
String responseString = IOUtils.toString(myConnection.getInputStream(), "UTF-8");
JSONObject responseJson = (JSONObject) new JSONParser().parse(responseString);
Set<String> keyValues = responseJson.keySet();
for (String key : keyValues) {
Data data = new Data(responseJson.get(key).toString());
Log.d("Data Element: ", data.getDataString());
dataList.add(data);
}
for (Data data : dataList) {
Log.d("Data List Element", data.getDataString());
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
dataAdapter.notifyDataSetChanged();
super.onPostExecute(aVoid);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.search_menu,menu);
MenuItem searchItem = menu.findItem(R.id.search_action);
SearchView searchView = (SearchView) searchItem.getActionView();
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
@Override
public boolean onQueryTextSubmit(String s) {
dataAdapter.getFilter().filter(s);
return false;
}
@Override
public boolean onQueryTextChange(String s) {
dataAdapter.getFilter().filter(s);
return false;
}
});
return true;
}
}

Answer 1

您必须保存两次列表，一次用于recyclerview，另一次用于筛选。

看看下面的工作示例

getUserModelListFiltered仅用于筛选目的。

public class UsersAdapter extends RecyclerView.Adapter<UsersAdapter.UsersAdapterVh> implements Filterable {
private List<UserModel> userModelList;
private List<UserModel> getUserModelListFiltered;
private Context context;
private SelectedUser selectedUser;
public UsersAdapter(List<UserModel> userModelList,SelectedUser selectedUser) {
this.userModelList = userModelList;
this.getUserModelListFiltered = userModelList;
this.selectedUser = selectedUser;
}
@NonNull
@Override
public UsersAdapter.UsersAdapterVh onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
context = parent.getContext();
return new UsersAdapterVh(LayoutInflater.from(context).inflate(R.layout.row_uses,null));
}
@Override
public void onBindViewHolder(@NonNull UsersAdapter.UsersAdapterVh holder, int position) {
UserModel userModel = userModelList.get(position);
String username = userModel.getUserName();
String prefix = userModel.getUserName().substring(0,1);
holder.tvUsername.setText(username);
holder.tvPrefix.setText(prefix);
}


@Override
public int getItemCount() {
return userModelList.size();
}
@Override
public Filter getFilter() {
Filter filter = new Filter() {
@Override
protected FilterResults performFiltering(CharSequence charSequence) {
FilterResults filterResults = new FilterResults();
if(charSequence == null | charSequence.length() == 0){
filterResults.count = getUserModelListFiltered.size();
filterResults.values = getUserModelListFiltered;
}else{
String searchChr = charSequence.toString().toLowerCase();
List<UserModel> resultData = new ArrayList<>();
for(UserModel userModel: getUserModelListFiltered){
if(userModel.getUserName().toLowerCase().contains(searchChr)){
resultData.add(userModel);
}
}
filterResults.count = resultData.size();
filterResults.values = resultData;
}
return filterResults;
}
@Override
protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
userModelList = (List<UserModel>) filterResults.values;
notifyDataSetChanged();
}
};
return filter;
}

public interface SelectedUser{
void selectedUser(UserModel userModel);
}
public class UsersAdapterVh extends RecyclerView.ViewHolder {
TextView tvPrefix;
TextView tvUsername;
ImageView imIcon;
public UsersAdapterVh(@NonNull View itemView) {
super(itemView);
tvPrefix = itemView.findViewById(R.id.prefix);
tvUsername = itemView.findViewById(R.id.username);
imIcon = itemView.findViewById(R.id.imageView);
itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
selectedUser.selectedUser(userModelList.get(getAdapterPosition()));
}
});

}
}
}