无法在Android应用中使用外部数据库

Question

I want to use my external datbase in MySQL . I have an archived database databse.db.zip and have copied it in the assets folder of my Android Java project. Finally I have created a class for opening the database:

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;
import com.readystatesoftware.sqliteasset.SQLiteAssetHelper;

public class databaseOpen extends SQLiteAssetHelper {

private static final String DATABASE_NAME = "parole.db";
private static final int DATABASE_VERSION = 1;

public databaseOpen(Context context) {

    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public String risposta(String parolain ){
    SQLiteDatabase db = getReadableDatabase();
    SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
    String[] selectionArgs = {"ciao"};
    Cursor c =db.query("prima", null, null,selectionArgs, null, null,   null);
    c.moveToFirst();

    return c.getString(0);
}
}

And i have reclaimed it in my main :

private databaseOpen db;

@Override
protected void onCreate(Bundle savedInstanceState) {
    db = new databaseOpen(this);
    Toast toast=Toast.makeText(this, db.risposta("ciao"), Toast.LENGTH_LONG);
}

but it doesn't work. Here is the output I'm getting:

09-26 15:20:23.761    1099-1099/? I/SQLiteAssetHelper successfully opened database parole.db
09-26 15:20:23.764    1099-1099/? E/SQLiteLog (1) no such table: prima
09-26 15:20:23.783    1099-1099/? D/AndroidRuntime Shutting down VM
09-26 15:20:23.801    1099-1099/? E/AndroidRuntime FATAL EXCEPTION: main
    Process: com.example.roby.jarvis, PID: 1099
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.roby.jarvis/com.example.roby.jarvis.Home}: android.database.sqlite.SQLiteException: no such table: prima (code 1): , while compiling: SELECT * FROM prima

Answer 1

i wanna use my external datbase in mysql , i have zipping this (databse.db.zip) and have copy this in assents folder on my java project

For the record, either you're using the wrong terminology or confused. Android, and the code in your post, works with SQLite. It cannot work with MySQL.

When something doesn't work, read the error message, which usually explains the problem, for example:

09-26 15:20:23.764 1099-1099/? E/SQLiteLog﹕ (1) no such table: prima

A table named "prima" does not exist in the file.

The next step to debug would be to check the content of the file on your PC, using the sqlite3 command line tool or similar, and see what tables it has ( .schema command).

Answer 2

First : You are not copying the Database file from your assets file to your device, which will obviously result into no such table found .

Try this code, its working for me. (Also i have commented different sections for your understanding)

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Build;
import android.util.Log;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
* Created by HP-HP on 23-07-2015.
*/
public class DataBaseHelper extends SQLiteOpenHelper {

//The Android's default system path of your application database.
private static String DB_PATH ;

private static String DB_NAME = "profanityv2";

private SQLiteDatabase myDataBase;

private final Context myContext;

/**
 * Constructor
 * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
 * @param context
 */
public DataBaseHelper(Context context) {

    super(context, DB_NAME, null, 1);

    if(android.os.Build.VERSION.SDK_INT >= 4.2){
        DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
    } else {
        DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
    }

    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 doesn't
 */
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 does't exist yet.
        try {
            myContext.deleteDatabase("profanity");
        } catch (Exception e1) {
            e1.printStackTrace();
        }
    }

    if(checkDB != null){

        checkDB.close();

    }

    return checkDB != null;
}

/**
 * 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.NO_LOCALIZED_COLLATORS|SQLiteDatabase.CREATE_IF_NECESSARY );

}

@Override
public synchronized void close() {

    if(myDataBase != null)
        myDataBase.close();

    super.close();

}

public Cursor getData() {
    Cursor c = null;
    try {
        c = myDataBase.rawQuery("SELECT * FROM profanity_table", null);
    } catch (Exception e) {
        e.printStackTrace();
    }
    // Note: Master is the one table in External db. Here we trying to access the records of table from external db.
    return c;
}


@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.

}

usage :

DataBaseHelper dataBaseHelper = new DataBaseHelper(this);

    try {
        dataBaseHelper.createDataBase();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    try {

        dataBaseHelper.openDataBase();

    }catch(SQLException sqle){

        throw sqle;

    }

    Cursor c = dataBaseHelper.getData();

    if(c!=null) {
        /* your cursor code */
        c.close();
    }


    dataBaseHelper.close();

*Note : Some Devices may not be able to able to copy the database to the device.(Known Devices : OnePlus)

Don't forget to add this permission

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

in your manifest.

Edit 1: OnePlus is able to copy the database to /data/data/<package-name>/databases/<filename>.db but it doesn't allow to access that data and i have no clue regarding that.