Android SQL 数据库 - 未找到 rawQuery() 源

Question

我知道有数十亿个关于 SQL 数据库的线程，但我没有找到任何解决我的问题的线程。我制作了一个名为 Beer Or No Beer 的应用程序这需要一个包含啤酒品牌及其国家/地区的 Arraylist。现在我想用 SQLite 管理这个列表。我使用 SQLite 数据库浏览器创建了一个数据库，并将该数据库复制到 Assets 文件夹(名称:sqbeerlist)中。现在我已经创建了一个 DatabaseHelper 类来打开文件并将其写入数组列表。但是当我想访问行时

Cursor c = myDataBase.rawQuery("SELECT _id, brand FROM " + DATABASE_TABLE, null);

DVM 崩溃并显示未找到源。我做错了什么？？

这是整个 HelperClass:

package com.celticwolf.alex;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream; 

import java.util.ArrayList;

import android.content.Context;

import android.database.Cursor;

import android.database.SQLException;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteDatabase.CursorFactory;

import android.database.sqlite.SQLiteException;

import android.database.sqlite.SQLiteOpenHelper;

public class DataBaseHelper extends SQLiteOpenHelper {

// The Androids default system path of your application database.

private static String DB_PATH = "/data/data/com.celticwolf.alex/databases/";

private static String DB_NAME = "sqbeerlist";

private static final String DATABASE_TABLE = "beers";

private SQLiteDatabase myDataBase;

public static final String KEY_ROWID = "_id";

public static final String KEY_NAME = "brand";

public static final String KEY_COUNTRY = "country";

private final Context myContext;

public DataBaseHelper(Context context) {

    super(context, DB_NAME, null, 1);

    this.myContext = context;

}

/**
 * 
 * Creates a empty database on the system and rewrites it with your own
 * 
 * database.
 * 
 * */

public void createDataBase() throws IOException {

    boolean dbExist = checkDataBase();

    if (dbExist) {

        // do nothing - database already exist

    } else {

        // By calling this method and empty database will be created into

        // the default system path

        // of your application so we are gonna be able to overwrite that

        // database with our database.

        this.getReadableDatabase();

        try {

            copyDataBase();

        } catch (IOException e) {

            throw new Error("Error copying database");

        }

    }

}

/**
 * 
 * Check if the database already exist to avoid re-copying the file each
 * 
 * time you open the application.
 * 
 * 
 * 
 * @return true if it exists, false if it doesnt
 */

private boolean checkDataBase() {

    SQLiteDatabase checkDB = null;

    try {

        String myPath = DB_PATH + DB_NAME;

        checkDB = SQLiteDatabase.openDatabase(myPath, null,

        SQLiteDatabase.OPEN_READONLY);

    } catch (SQLiteException e) {

        // database doest exist yet.

    }

    if (checkDB != null) {

        checkDB.close();

    }

    return checkDB != null ? true : false;

}

/**
 * 
 * Copies your database from your local assets-folder to the just created
 * 
 * empty database in the system folder, from where it can be accessed and
 * 
 * handled. This is done by transfering bytestream.
 * 
 * */

private void copyDataBase() throws IOException {

    // Open your local db as the input stream

    InputStream myInput = myContext.getAssets().open(DB_NAME);

    // Path to the just created empty db

    String outFileName = DB_PATH + DB_NAME;

    // Open the empty db as the output stream

    OutputStream myOutput = new FileOutputStream(outFileName);

    // transfer bytes from the inputfile to the outputfile

    byte[] buffer = new byte[1024];

    int length;

    while ((length = myInput.read(buffer)) > 0) {

        myOutput.write(buffer, 0, length);

    }

    // Close the streams

    myOutput.flush();

    myOutput.close();

    myInput.close();

}

public void openDataBase() throws SQLException {

    // Open the database

    String myPath = DB_PATH + DB_NAME;

    myDataBase = SQLiteDatabase.openDatabase(myPath, null,     SQLiteDatabase.OPEN_READONLY);

}

@Override
public synchronized void close() {

    if (myDataBase != null)

        myDataBase.close();

    super.close();

}

public ArrayList<String> gettheArray() {

    ArrayList<String> result = new ArrayList<String>();

    try {

        openDataBase();

    }catch(SQLException sqle){

        throw sqle;

    }

    Cursor c = myDataBase.rawQuery("SELECT _id, brand FROM " + DATABASE_TABLE, null);

    c.moveToFirst();

    // Check if our result was valid.

    if (c != null) {

        // Loop through all Results

        do {

            result.add(c.getString(c.getColumnIndex(KEY_NAME)));

        } while (c.moveToNext());

    }

    close();

    return result;

}

@Override
public void onCreate(SQLiteDatabase db) {

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

// Add your public helper methods to access and get content from the

// database.

// You could return cursors by doing "return myDataBase.query(....)" so it'd

// be easy

// to you to create adapters for your views.

}

下面是我访问类的方式:

DataBaseHelper myDbHelper = new DataBaseHelper(null);
    myDbHelper = new DataBaseHelper(this);

    try {
         myDbHelper.createDataBase();

} catch (IOException ioe) {

    throw new Error("Unable to create database");

}

            ArrayList<String> thelist = myDbHelper.gettheArray();

谢谢，我希望有人能提供帮助(:

问题已解决!这是正确的代码!这个标志标志着变化:c==3

package com.celticwolf.alex;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.util.ArrayList;

import android.content.Context;

import android.database.Cursor;

import android.database.SQLException;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteDatabase.CursorFactory;

import android.database.sqlite.SQLiteException;

import android.database.sqlite.SQLiteOpenHelper;

public class DataBaseHelper extends SQLiteOpenHelper {

// The Android's default system path of your application database.

private static String DB_PATH = "/data/data/com.celticwolf.alex/databases/";

private static String DB_NAME = "sqbeerlist.sqlite";

private static final String DATABASE_TABLE = "beers";

private SQLiteDatabase myDataBase;

public static final String KEY_ROWID = "_id";

public static final String KEY_NAME = "brand";

public static final String KEY_COUNTRY = "country";

private final Context myContext;

public DataBaseHelper(Context context) {

    super(context, DB_NAME, null, 1);

    this.myContext = context;

}

/**
 * 
 * Creates a empty database on the system and rewrites it with your own
 * 
 * database.
 * 
 * */

public void createDataBase() throws IOException {

    boolean dbExist = checkDataBase();
    SQLiteDatabase db_Read = null;  // c==3

    if (dbExist) {

        // do nothing - database already exist

    } else {

        // By calling this method and empty database will be created into
        // the default system path
        // of your application so we are gonna be able to overwrite that
        // database with our database.

        db_Read = this.getReadableDatabase();  // c==3
        db_Read.close();  // c==3

        try {

            copyDataBase();

        } catch (IOException e) {

            throw new Error("Error copying database");

        }

    }

}

/**
 * 
 * Check if the database already exist to avoid re-copying the file each
 * 
 * time you open the application.
 * 
 * 
 * 
 * @return true if it exists, false if it doesnt
 */

private boolean checkDataBase() {

    SQLiteDatabase checkDB = null;

    try {

        String myPath = DB_PATH + DB_NAME;

        checkDB = SQLiteDatabase.openDatabase(myPath, null,
                 (SQLiteDatabase.OPEN_READONLY | SQLiteDatabase.NO_LOCALIZED_COLLATORS));  // c==3

    } catch (SQLiteException e) {

        // database doesnt exist yet.

    }

    if (checkDB != null) {

        checkDB.close();

    }

    return checkDB != null ? true : false;

}

/**
 * 
 * Copies your database from your local assets-folder to the just created
 * 
 * empty database in the system folder, from where it can be accessed and
 * 
 * handled. This is done by transfering bytestream.
 * 
 * */

private void copyDataBase() throws IOException {

    // Open your local db as the input stream

    InputStream myInput = myContext.getAssets().open(DB_NAME);

    // Path to the just created empty db

    String outFileName = DB_PATH + DB_NAME;

    // Open the empty db as the output stream

    OutputStream myOutput = new FileOutputStream(outFileName);

    // transfer bytes from the inputfile to the outputfile

    byte[] buffer = new byte[1024];

    int length;

    while ((length = myInput.read(buffer)) > 0) {

        myOutput.write(buffer, 0, length);

    }

    // Close the streams

    myOutput.flush();
    myOutput.close();
    myInput.close();

}

public void openDataBase() throws SQLException {

    // Open the database

    String myPath = DB_PATH + DB_NAME;

    myDataBase = SQLiteDatabase.openDatabase(myPath, null, (SQLiteDatabase.OPEN_READONLY | SQLiteDatabase.NO_LOCALIZED_COLLATORS)); // c==3

}

@Override
public synchronized void close() {

    if (myDataBase != null)

        myDataBase.close();

    super.close();

}

public ArrayList<String> gettheArray() {

    ArrayList<String> result = new ArrayList<String>();

    try {

        openDataBase();

    }catch(SQLException sqle){

        throw sqle;

    }

    Cursor c = myDataBase.rawQuery("SELECT _id, brand FROM " + DATABASE_TABLE, null);

    c.moveToFirst();

    // Check if our result was valid.

    if (c != null) {

        // Loop through all Results

        do {

            result.add(c.getString(c.getColumnIndex(KEY_NAME)));

        } while (c.moveToNext());
    }
    close();
    return result;
}

@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
// Add your public helper methods to access and get content from the
// database.
// You could return cursors by doing "return myDataBase.query(....)" so itd
// be easy
// to you to create adapters for your views.
}

Answer 1

前段时间我在最初复制数据库时遇到了这个问题。

我最终在第一次运行应用程序时使用 csv 格式的资源( Assets 或原始资源)从头开始创建数据库(显然这可能会占用更多空间)

看看this thread看看是否有帮助。