类型不匹配:无法从java.lang.String转换为String

我不明白为什么我得到这个错误!

public static class RoomsArrayAdapter extends ArrayAdapter{
****
private String rmName;
    private ArrayList st_list = new ArrayList();

public View getView(int position, View convertView, ViewGroup parent){                      
        View rowView = convertView; 
        LayoutInflater inflater = (LayoutInflater) raaContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        rowView = inflater.inflate(R.layout.room_layout, parent, false);
        rmName = st_list.get(position).toString();

rmName = st_list.get(position).toString();

有我的进口:

import android.text.Editable;
import android.text.TextUtils;
import android.text.TextWatcher;
import android.app.AlertDialog;
import android.content.ComponentName;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.DialogInterface.OnClickListener;
import android.content.pm.PackageManager;
import android.graphics.Color;
import android.provider.Settings;
import android.util.Log;
import android.util.TypedValue;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.inputmethod.CompletionInfo;
import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import android.R.color;

第一次在我的ArrayAdapter的getView()中将onTextChanged方法添加到AutoCompleteTextView后出现错误.我尝试重新启动Eclipse,但它对我没有帮助.