从现有的.sqlite文件读取Android数据库

Question

I would like to read database from an existing file.

I have copied the .sqlite database to asset folder. I can see the .sqlite file under DDMS explorer in /data/data//databases/

However when I run a "c = db.rawQuery("SELECT count(*) FROM sqlite_master WHERE type = 'table'", null);"

It only returns the android_metadata table and not the other table from my database which was created in Firefox SQLite Manager.

*NOTE, I will post both my DatabaseHandler and Database Activity files, for any modification please supply the FULL code (modify my existing files) and the reason for this is that I am new to Android and pieces of codes confuse me as to where in the class I need to paste, replace or append etc therefore I would appreciate FULL codes.

Database Handler:

    package com.mypackage.lm;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;

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.util.Log;

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final String DB_NAME  = "lm.sqlite";
    private static final int DB_VERSION  = 1;
    private static final String TABLE_LM = "lmtable";
    private static final String LOG_TAG = "debugger";
    private static final String DB_PATH = "context.getDatabasePath(DatabaseHelper.DB_NAME).getParentFile()";

    private SQLiteDatabase myDB; 
    private Context context;

    public DatabaseHelper(Context context) {
    super(context, DB_NAME, null, DB_VERSION);
    this.context = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub

    }

    @Override
    public synchronized void close(){
    if(myDB!=null){
        myDB.close();
    }
    super.close();
    }

    /***
     * Check if the database is exist on device or not
     * @return
     */
    private boolean checkDataBase() {
    SQLiteDatabase tempDB = null;
    try {
        String myPath = DB_PATH + DB_NAME;
        tempDB = SQLiteDatabase.openDatabase(myPath, null,
            SQLiteDatabase.OPEN_READWRITE);
    } catch (SQLiteException e) {
        Log.e("ts01 - check", e.getMessage());
    }
    if (tempDB != null)
        tempDB.close();
    return tempDB != null ? true : false;
    }

/***
 * Copy database from source code assets to device
 * @throws IOException
 */
public void copyDataBase() throws IOException{
    try {
    InputStream myInput = context.getAssets().open(DB_NAME);
    String outputFileName = DB_PATH + DB_NAME;
    OutputStream myOutput = new FileOutputStream(outputFileName);

    byte[] buffer = new byte[1024];
    int length;

    while((length = myInput.read(buffer))>0){
        myOutput.write(buffer, 0, length);
    }

    myOutput.flush();
    myOutput.close();
    myInput.close();
    } catch (Exception e) {
    Log.e("ts02 - copyDatabase", e.getMessage());
    }

    }

/***
 * Open database
 * @throws SQLException
 */
    public void openDataBase() throws SQLException{
        String myPath = DB_PATH + DB_NAME;
        myDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}

    /***
     * Check if the database doesn't exist on device, create new one
     * @throws IOException
     */
    public void createDataBase() throws IOException {
        boolean dbExist = checkDataBase();        

        if (dbExist) {
            System.out.println("Database DOES exist");

        } else {
        System.out.println("Database DOESN'T exist");
        this.getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException e) {
            Log.e("ts03 - create", e.getMessage());
        }
        }
    }


    public List<String> getAllUsers(){
        List<String> listUsers = new ArrayList<String>();
        SQLiteDatabase db = this.getWritableDatabase();

        Cursor c;

        try {
        //c = db.rawQuery("SELECT * FROM " + TABLE_LM , null);
        //c = db.rawQuery("SELECT name FROM sqlite_master WHERE type = 'table'" , null);
        //c = db.rawQuery("SELECT count(*) FROM sqlite_master WHERE type = 'table' AND name != 'android_metadata' AND name != 'sqlite_sequence'", null);
        c = db.rawQuery("SELECT count(*) FROM sqlite_master WHERE type = 'table'", null);
        if(c == null) return null;

        String name;
        c.moveToFirst();
        do {            
            name = c.getString(0);            
            listUsers.add(name);
        } while (c.moveToNext()); 
        c.close();
        } catch (Exception e) {
        Log.e("ts04", e.getMessage());
        }

        db.close();        

        return listUsers;
    }

}

Database Activity:

    package com.mypackage.lm;

import java.io.IOException;
import java.util.List;

import com.mypackage.lm.R.id;

import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class DatabaseActivity extends MainActivity {

        DatabaseHelper dbHeplper;
        ListView lvUsers;
        ListAdapter adapter;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.db_return);



        dbHeplper = new DatabaseHelper(getApplicationContext());


        try {
            dbHeplper.createDataBase();
        } catch (IOException e) {
            e.printStackTrace();
        }

        lvUsers = (ListView)findViewById(id.listViewDB);
         List<String> listUsers = dbHeplper.getAllUsers();

        if(listUsers != null){
            adapter = new ArrayAdapter<String>(getApplicationContext(),
                android.R.layout.simple_list_item_1, android.R.id.text1,
                listUsers);
            lvUsers.setAdapter(adapter);
        }

        }

        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
        }


    }

Answer 1

Maybe I am wrong and this is not the answer, but if this should be Your path:

   private static final String DB_PATH = "context.getDatabasePath(DatabaseHelper.DB_NAME).getParentFile()";

Then You will have no file path. You set a method inside the quotation marks, so the path will be:

    context.getDatabasePath(DatabaseHelper.DB_NAME).getParentFile()lm.sqlite

I think what You wanted to do is:

        private static final String DB_PATH = context.getDatabasePath(DatabaseHelper.DB_NAME).getParentFile();

Answer 2

OK, for some strange reason it worked, I uninstalled the APP from the Virtual Device then re-ran it, after the apk was re-installed I am able to see the database tables (android_metadata and lmtable).

Now my next phase is to determine HOW my android will know that changes are made to the database and needs to be recopied despite "if DB exist" statement, I read about incrementing the DB version number so maybe that was the issue but as for now, uninstalling app from virtual device did the trick.