So I have two contexts (service and UI activity) running from the same process, and also I use traditional's wrapped way to get write handle:
package me.soexample.sobad;
import java.util.concurrent.atomic.AtomicInteger;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DatabaseManager {
private static AtomicInteger mOpenCounter = new AtomicInteger();
private static DatabaseManager instance;
private static DatabaseHelper mDatabaseHelper;
private SQLiteDatabase mDatabase;
public static synchronized void initializeInstance(DatabaseHelper helper) {
if (instance == null) {
instance = new DatabaseManager();
mDatabaseHelper = helper;
}
}
public static synchronized DatabaseManager getInstance() {
if (instance == null) {
throw new IllegalStateException(DatabaseManager.class.getSimpleName() +
" is not initialized, call initializeInstance(..) method first.");
}
return instance;
}
public SQLiteDatabase openDatabase() {
if(mOpenCounter.incrementAndGet() == 1) {
// Opening new database
mDatabase = mDatabaseHelper.getWritableDatabaseAlt();
}
return mDatabase;
}
public void closeDatabase() {
if(mOpenCounter.decrementAndGet() == 0) {
// Closing database
mDatabase.close();
}
}
}
As if it can not be expected, it often results in:
04-11 04:24:51.738: E/gsmspy(24331): java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /storage/sdcard0/my.db
04-11 04:24:51.738: E/gsmspy(24331): at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:55)
04-11 04:24:51.738: E/gsmspy(24331): at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1310)
04-11 04:24:51.738: E/gsmspy(24331): at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1253)
04-11 04:24:51.738: E/gsmspy(24331): at me.soexample.sogood.somethod2(sogood.java:51)
04-11 04:24:51.738: E/gsmspy(24331): at me.soexample.sogood.somethod(sogood.java:41)
As you can see, there are no references to DatabaseManager; so it seems to be a multithreading problem. Now, what do I do to have a guaranteed ability to write to DB object returned from such wrapper?
The original (see "Approach #2") class was more of smart something. Now, a DatabaseHelper (SQLiteOpenHelper) is constructed in DatabaseManager(), removing the problem (no more two SQLiteOpenHelper's working in parallel worst-case)