从一个或多个表的Android SQLite db返回的空数据记录

在过去的两天里，我一直在努力解决这个问题。我试图创建一个从数据库查询填充的列表视图，这似乎很简单。由于我将管理多个表，因此我创建了一个数据库帮助器类来管理插入和删除。但它并没有始终如一地发挥作用，或者根本没有发挥作用

当我尝试使用定义的函数之一查询表时，db返回具有XX个记录数的游标，但列数据为空。实际上，我看到了多行分隔符，但每行都是空的

我在这个问题上有点为难，希望能得到任何帮助。下面是DB助手类

数据库助手类

package org.data.agroassistant;

import static android.provider.BaseColumns._ID;
import static org.data.agroassistant.Constants.*;

import java.net.URL;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class AgroAssistantDB extends SQLiteOpenHelper {

    private static final String CREATE_TABLE_FARMERS = "create table " + FARMERS_TABLE + " ( " 
        + _ID + " integer primary key autoincrement, "
        + FARMER_ID + " int not null, "
        + FARMER_FNAME + " text not null, "
        + FARMER_LNAME + " text not null, "
        + FARMER_SIZE + " text not null);";

    private static final String CREATE_TABLE_FARMS = "create table " + FARMS_TABLE + " ( " 
        + _ID + " integer primary key autoincrement, "
        + FARM_ID + " integer not null, " 
        + FARM_FARMER_ID + " integer not null, "
        + FARM_SIZE + " text not null, "
        + FARM_PARISH + " text not null, "
        + FARM_EXTENSION + " text not null, "
        + FARM_DISTRICT + " text not null, "
        + FARM_LAT + " long not null, "
        + FARM_LONG + " long not null);"; 

    private static final int DATABASE_VERSION = 1;

    private SQLiteDatabase db;

    public AgroAssistantDB(Context ctx) {
        super(ctx, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase dbl) {
        try {
            dbl.execSQL(CREATE_TABLE_FARMERS);
            Log.d("AgroAssistant", "Create Farmers table: " + CREATE_TABLE_FARMERS);
            //dbl.execSQL(CREATE_TABLE_FARMS);
            //Log.d("AgroAssistant", "Create Farms table: " + CREATE_TABLE_FARMS);
        } catch (RuntimeException e) {
            Log.d("AgroAssistant", "Unable to create tables: " + CREATE_TABLE_FARMERS + CREATE_TABLE_FARMS);
        }


    }

    @Override
    public void onUpgrade(SQLiteDatabase dbl, int oldVersion, int newVersion) {
        Log.w("AgroAssistant", "Upgrading database from version " + oldVersion + " to "
                        + newVersion + ", which will destroy all old data");
        dbl.execSQL("DROP TABLE IF EXISTS " + FARMERS_TABLE);
        dbl.execSQL("DROP TABLE IF EXISTS " + FARMS_TABLE);
        Log.d("AgroAssistant", "Upgrade step: " + "DROP TABLE IF EXISTS " + FARMERS_TABLE + FARMS_TABLE);
        onCreate(dbl);
    }

    /*
     * Userdefined function used to run rawQueries again specific tables
     */
    public Cursor rawQuery(String tableName, String tableColumns, String queryParams) {
        db = this.getReadableDatabase();
        Log.d("AgroAssistant", "Raw Query Insertion: SELECT "+ tableColumns + " FROM " + tableName + " WHERE " + queryParams);
        Cursor cursor = db.rawQuery("SELECT "+ tableColumns + " FROM " + tableName +" WHERE " + queryParams, null);
        Log.d("AgroAssistant", "Raw Query Result: Returned " + cursor.getCount() + " record(s)");
        return cursor;
    }

    public Cursor getFarmers() {
        db = this.getReadableDatabase();
        //Cursor cursor = db.query(FARMERS_TABLE, FROM_FARMERS, null, null, null, null, null);
        Cursor cursor = db.query(FARMERS_TABLE, new String[] {"*"}, null, null, null, null, null);
        return cursor;
    }

    public boolean insertFarmer(int id, String firstname, String lastname, String farmersize) {
        db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(FARMER_ID, id);
        values.put(FARMER_FNAME, firstname);
        values.put(FARMER_LNAME, lastname);
        values.put(FARMER_SIZE, farmersize);
        try {
            db.insertOrThrow(FARMERS_TABLE, null, values);
            Log.d("AgroAssistant", "Insert Farmer: " + id + " " + firstname + " " + lastname + " " + farmersize);
            //db.close();
            return true;
        }
        catch (RuntimeException e) {
            //db.close();
            Log.e("AgroAssistant","Farmer Insertion Exception: "+e.toString());
            return false;
        }
    }

    public boolean deleteFarmer(Long farmerId) {
        db = this.getWritableDatabase();
        if (db.delete(FARMERS_TABLE, _ID + '=' + farmerId.toString(), null) > 0) {
            db.close();
            return true;
        } else {
            db.close();
            return false;
        }
    }

    public boolean insertFarm(int fid, int pid, int p_size, int latitude, int longtitude, String p_parish, String p_extension, String p_district) {
        db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(FARM_ID, pid);
        values.put(FARM_FARMER_ID, fid);
        values.put(FARM_SIZE, p_size);
        values.put(FARM_LAT, latitude);
        values.put(FARM_LONG, longtitude);
        values.put(FARM_PARISH, p_parish);
        values.put(FARM_EXTENSION, p_extension);
        values.put(FARM_DISTRICT, p_district);

        try {
            db.insertOrThrow(FARMS_TABLE, null, values);
            Log.d("AgroAssistant", "Insert Farm: " + fid + " " + pid + " " + p_size + " " + latitude + " " + longtitude + " " + p_extension + " " + p_district);
            db.close();
            return true;
        }
        catch (RuntimeException e) {
            db.close();
            Log.e("AgroAssistant","Farm Insertion Exception: "+e.toString());
            return false;
        }
    }

    public Cursor getFarms() {
        db = this.getReadableDatabase();
        Cursor cursor = db.query(FARMS_TABLE, FROM_FARMS, null, null, null, null, null);
        return cursor;
    }

    public boolean deleteFarm(Long farmId) {
        db = this.getWritableDatabase();
        if (db.delete(FARMS_TABLE, _ID + '=' + farmId.toString(), null) > 0) {
            db.close();
            return true;
        } else {
            db.close();
            return false;
        }
    }

}

我在DB类中使用的所有常量定义如下：

package org.data.agroassistant;

import android.provider.BaseColumns;

public interface Constants extends BaseColumns {

    public static final int FARMER_SEARCH = 0;
    public static final int FARM_SEARCH = 1;
    public static final int CROP_SEARCH = 2;
    public static final int PRICE_SEARCH = 3;

    /*====DATABASE CONSTANTS======================
     * Constants used by the database adapter class
     */
    public static final String DATABASE_NAME = "agroassistant";
    public static final String FARMERS_TABLE= "farmers";
    public static final String FARMS_TABLE= "farms";

    //Columns in the Farmers table
    public static final String FARMER_ID = "farmerid";
    public static final String FARMER_FNAME = "firstname";
    public static final String FARMER_LNAME = "lastname";
    public static final String FARMER_SIZE = "farmersize";

    //Columns in the Farms table
    public static final String FARM_ID = "farmid";
    public static final String FARM_FARMER_ID = "farmerid";
    public static final String FARM_SIZE = "propertysize";
    public static final String FARM_PARISH = "parish";
    public static final String FARM_EXTENSION = "extension";
    public static final String FARM_DISTRICT = "district";
    public static final String FARM_LAT = "xcoord";
    public static final String FARM_LONG = "ycoord";

    public static final String[] FROM_FARMERS = {_ID, FARMER_ID, FARMER_FNAME, FARMER_LNAME, FARMER_SIZE};
    public static final String[] FROM_FARMS = {_ID, FARM_ID, FARM_FARMER_ID, FARM_SIZE, FARM_PARISH, FARM_EXTENSION, FARM_DISTRICT, FARM_LAT, FARM_LONG};

    public static final String FROM_S_FARMERS = _ID + ", " + FARMER_ID + ", " + FARMER_FNAME + ", " + FARMER_LNAME + ", " + FARMER_SIZE;
    public static final String FROM_S_FARMS = _ID + ", " + FARM_ID + ", " + FARM_FARMER_ID + ", " + FARM_SIZE + ", " + FARM_PARISH + ", " + FARM_EXTENSION + ", " + FARM_DISTRICT + ", " + FARM_LAT + ", " + FARM_LONG;

}

下面是尝试使用db helper对象的listactivity

package org.data.agroassistant;

import static org.data.agroassistant.Constants.*;

import java.util.Arrays;

import android.app.ListActivity;
import android.database.Cursor;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;

public class ResultView extends ListActivity {

    private AgroAssistantDB agroDB;
    private Cursor resultsCursor;
    private int searchType;
    private String searchParams;

    private static final int[] FARMER_TO = {R.id.txt_farmer_id, R.id.txt_farmer_fname, R.id.txt_farmer_lname};

    /*
     * @see android.app.Activity#onCreate(android.os.Bundle)
     * @Intent Params: 
     *  (int)       searchType      Type of search performed {Farmer,Farm,Crop,Price}
     *  (String)    searchParams    String of WHERE clause for query
     */
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.result_search);
        Bundle b = getIntent().getExtras();
        agroDB = new AgroAssistantDB(this);
        //searchType = b.getInt("searchType");
        //final String searchResponse = b.getString("searchResponse");
        //final String searchParams = b.getString("searchParams");



        /*
         * Need
         *  Cursor
         *  CursorAdapter
         *  SQL query (params)
         *  SQL (from)
         */
        searchType = FARMER_SEARCH;
        searchParams = FARMER_ID + "=1102018039";
        try {
            switch(searchType) {
            case(FARMER_SEARCH): 
                //resultsCursor = agroDB.rawQuery(FARMERS_TABLE, FROM_S_FARMERS, searchParams);
                break;
            case (FARM_SEARCH):
                resultsCursor = agroDB.rawQuery(FARMS_TABLE, FROM_S_FARMS, searchParams);
                break;
            case (CROP_SEARCH):
                resultsCursor = agroDB.rawQuery(CROPS_TABLE, "FROM_S_CROPS", searchParams);
                break;
            case (PRICE_SEARCH):
                resultsCursor = agroDB.rawQuery(PRICES_TABLE, "FROM_PRICES", searchParams);
                break;
            default:
                break;
            }

            resultsCursor = agroDB.getFarmers();
            startManagingCursor(resultsCursor);
            showResults(resultsCursor);
        } finally {
            //agroDB.close();
        }
    }

    private void showResults(Cursor cursor){
        SimpleCursorAdapter results = null;
        switch(searchType) {
        case(FARMER_SEARCH): 
            ListView list = getListView();

            Cursor cursorSelect = (Cursor) list.getItemAtPosition(0);
            cursor.getColumnNames();
            Log.d("AgroAssistant", "showResults: Cusor contains " + cursor.getCount() + " record(s)");
            Log.d("AgroAssistant", "showResults: Cusor contains " + cursor.getColumnCount() + " column(s)");
            Log.d("AgroAssistant", "showResults: Cusor contains " + Arrays.toString(cursor.getColumnNames()));

            /*
            Log.d("AgroAssistant", "ID " + cursorSelect.getString(cursor.getColumnIndex(_ID)));
            Log.d("AgroAssistant", "FID " + cursorSelect.getString(cursor.getColumnIndex("farmerid")));
            Log.d("AgroAssistant", "FNAME " + cursorSelect.getString(cursor.getColumnIndex("fname")));
            Log.d("AgroAssistant", "LNAME " + cursorSelect.getString(cursor.getColumnIndex(FARMER_LNAME)));
            */

            results = new SimpleCursorAdapter(this, R.layout.farmer_row, cursor, new String[] {FARMER_ID, FARMER_FNAME, FARMER_LNAME}, FARMER_TO);
            break;
        case (FARM_SEARCH):
            //results = new SimpleCursorAdapter(this, R.layout.farm_row, cursor, new String[] {FEED_TITLE}, TO);
            break;
        case (CROP_SEARCH):
            //results = new SimpleCursorAdapter(this, R.layout.crop_row, cursor, new String[] {FEED_TITLE}, TO);
            break;
        case (PRICE_SEARCH):
            //results = new SimpleCursorAdapter(this, R.layout.price_row, cursor, new String[] {FEED_TITLE}, TO);
            break;
        default:
            break;
        }

        setListAdapter(results);
    }

如有任何想法或帮助，将不胜感激

---

*编辑：我从手机上取下sqlite db，然后在sqlite浏览器中打开它。所有输入的记录都在那里。此外，当在浏览器视图中写入查询时，查询也能正常工作。

结果表明，RPO问题与我使用的行布局有关。Android给出了无法附加线程的错误消息

最后switch语句中的结果行是否已注释掉？