I’m new to the Android SQLite whole thing. This is what I have:
- I have
db.sqlitein myassetsfolder. - The intent of the db is to READ ONLY. The user will not write to it.
- When the app gets updated, the
db.sqlitewill be replaced be a new db (I’ll delete the old file from the project and add the new one).
What I’m concerned about is:
- Will the old db file gets deleted? (that’s what I want; replacing the old one with the new one)
- Why ask? Because when I debug my app, each time I update the db file, I need to uninstall the app from the device in order to force the update. Will the users need to do the same when they update my app from the play store? I’m afraid from that.
- Will this be affected by how I implement onCreate(SQLiteDatabase) and onUpgrade(SQLiteDatabase, int, int)?
- If yes, what is the proper way to implement them to meet my requirement?
This is how I extends the SQLiteOpenHelper class. I followed a tutorial I found in the internet:
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
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{
//The Android's default system path of your application database.
private static String DB_PATH = "/data/data/com.mydomain.myapp/databases/";
private static String DB_NAME = "db.sqlite";
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);
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
Log.i("myapp", "database already exist");
}else{
Log.i("myapp", "database NOT exist");
//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.
}
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_READWRITE);
}
@Override
public synchronized void close() {
if(myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
// My public helper methods to access and get content from the database go here
You can’t replace database in
onUpgrade()because in this method the database is already in use. You have to do it before the database is open, like in a constructor of yourDatabaseHelper. As you can’t useonUpgrade(), you have to manage database versioning by yourself. UsingSharedPreferencesis a good way for it. You check if your database exists (if it is already copied fromassetsdirectory) and check the version if database exists. Now you can delete old database and copy new one fromassets.See implementation below.
To mark your updated application is published with new database in
assetsjust incermentDATABASE_VERSIONconstant.