How do I use a database that exists in Android applications?

Asked 2 years ago, Updated 2 years ago, 46 views

I've already created a database with SQLite. I want to use this database file in my Android project. How can I access an existing database instead of creating a new one?

sqlite eclipse android java

2022-09-21 20:11

1 Answers

private static String DB_NAME ="YourDbName"; // Database name Enter the name of the database you created in YourDbName. And put the database in the asset folder. If the name of the database is orderDB, private static String DB_NAME ="ordersDB"; You can do it in this way.

DataHelper.class

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

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

public class DataBaseHelper extends SQLiteOpenHelper
{
    Tag name to output to private static String TAG = "DataBaseHelper"; //Logcat 
    //The path of the database from the device device
    private static String DB_PATH = "";
    private static String DB_NAME = "YourDbName"; // Database name 
    private SQLiteDatabase mDataBase;
    private final Context mContext;

    public DataBaseHelper(Context context)
    {
        super(context, DB_NAME, null, 1);//1 is the database version
        if(android.os.Build.VERSION.SDK_INT >= 17){
           DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
        }
        else
        {
           DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
        }
        this.mContext = context;
    }

    public void createDataBase() throws IOException
    {
        //If the database does not exist, copy it from the asset folder. 

        boolean mDataBaseExist = checkDataBase();
        if(!mDataBaseExist)
        {
            this.getReadableDatabase();
            this.close();
            try
            {
                //Copy the database from assests
                copyDataBase();
                Log.e(TAG, "createDatabase database created");
            }
            catch (IOException mIOException)
            {
                throw new Error("ErrorCopyingDataBase");
            }
        }
    }

    ///data/data/your package/databases/DaName <-Check if the database exists in this path
    private boolean checkDataBase()
    {
        File dbFile = new File(DB_PATH + DB_NAME);
        //Log.v("dbFile", dbFile + "   "+ dbFile.exists());
        return dbFile.exists();
    }

    Copy the database from the //assets folder. 
    private void copyDataBase() throws IOException
    {
        InputStream mInput = mContext.getAssets().open(DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        OutputStream mOutput = new FileOutputStream(outFileName);
        byte[] mBuffer = new byte[1024];
        int mLength;
        while ((mLength = mInput.read(mBuffer))>0)
        {
            mOutput.write(mBuffer, 0, mLength);
        }
        mOutput.flush();
        mOutput.close();
        mInput.close();
    }

    //Open the database to write queries. 
    public boolean openDataBase() throws SQLException
    {
        String mPath = DB_PATH + DB_NAME;
        //Log.v("mPath", mPath);
        mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.CREATE_IF_NECESSARY);
        //mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.NO_LOCALIZED_COLLATORS);
        return mDataBase != null;
    }

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

DataAdapter.class

import java.io.IOException;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;

public class TestAdapter
{
    protected static final String TAG = "DataAdapter";

    private final Context mContext;
    private SQLiteDatabase mDb;
    private DataBaseHelper mDbHelper;

    public TestAdapter(Context context)
    {
        this.mContext = context;
        mDbHelper = new DataBaseHelper(mContext);
    }

    public TestAdapter createDatabase() throws SQLException
    {
        try
        {
            mDbHelper.createDataBase();
        }
        catch (IOException mIOException)
        {
            Log.e(TAG, mIOException.toString() + "  UnableToCreateDatabase");
            throw new Error("UnableToCreateDatabase");
        }
        return this;
    }

    public TestAdapter open() throws SQLException
    {
        try
        {
            mDbHelper.openDataBase();
            mDbHelper.close();
            mDb = mDbHelper.getReadableDatabase();
        }
        catch (SQLException mSQLException)
        {
            Log.e(TAG, "open >>"+ mSQLException.toString());
            throw mSQLException;
        }
        return this;
    }

    public void close()
    {
        mDbHelper.close();
    }

     public Cursor getTestData()
     {
         try
         {
             String sql ="SELECT * FROM myTable";

              Cursor mCur = mDb.rawQuery(sql, null);
             if (mCur!=null)
             {
                mCur.moveToNext();
             }
             return mCur;
         }
         catch (SQLException mSQLException)
         {
             Log.e(TAG, "getTestData >>"+ mSQLException.toString());
             throw mSQLException;
         }
     }
}

And

TestAdapter mDbHelper = new TestAdapter(urContext);
mDbHelper.createDatabase();
mDbHelper.open();

Cursor testdata = mDbHelper.getTestData();

mDbHelper.close();

You can write it like this.


2022-09-21 20:11

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