Android SQL数据库 - rawQuery()源未找到

时间:2012-04-11 12:44:16

标签: android sql database arraylist cursor

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。 我做了一个名为Beer Or No Beer的应用程序,需要一个啤酒品牌及其国家的Arraylist。现在我想用SQLite管理这个列表。我用SQLite数据库浏览器创建了一个数据库,并将数据库复制到assets文件夹(名称:sqbeerlist)。 现在我创建了一个DatabaseHelper类来打开文件并将其写入arraylist。 但是当我想用

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

DVM崩溃,它说Source Not Found。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 gettheArray() {

        ArrayList result = new ArrayList();

        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.

}
 

And here is how I access the class:

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();

Thank you and I hope someone can help (:

=========================================================================================== Problem Solved! Here is the correct Code! This sign marks the changes: c==3

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();

2 个答案:

答案 0 :(得分:2)

我不久前遇到了这个问题,最初是在复制数据库。

我最终在应用程序首次运行时使用csv格式的资源(资产或原始)从头开始创建数据库(显然这可能占用更多空间)

查看this thread,看看是否有帮助。

答案 1 :(得分:2)

您需要使用SQLiteDatabase.NO_LOCALIZED_COLLATORS打开数据库,因为当您在android之外创建数据库时,它不包含android框架所需的表android_metadata

所以,打开你的数据库如下:

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

希望它能解决你的问题