Question

My application parses three different XML’s and saves them to database. It worked fine as long as I used AsyncTask, with progress dialog, because all of them were executed one after another. I’m now starting to parse that data simultaneously in three different threads (+UI thread). Now these four threads fight for database, and sometimes crash, always if UI thread is being used. I get the following errors:

 ERROR/AndroidRuntime(651): Caused by: java.lang.IllegalStateException: database /data/data/edu.activity/databases/vreme already closed

then another time i get

 INFO/System.out(667): XML Pasing5 Excpetion = java.lang.IllegalStateException: database not open

or this one

01-30 00:56:05.232: ERROR/AndroidRuntime(731): FATAL EXCEPTION: Thread-11
01-30 00:56:05.232: ERROR/AndroidRuntime(731): java.lang.IllegalStateException: database not open
01-30 00:56:05.232: ERROR/AndroidRuntime(731):     at android.database.sqlite.SQLiteDatabase.insertWithOnConflict(SQLiteDatabase.java:1493)
01-30 00:56:05.232: ERROR/AndroidRuntime(731):     at android.database.sqlite.SQLiteDatabase.insert(SQLiteDatabase.java:1410)
01-30 00:56:05.232: ERROR/AndroidRuntime(731):     at edu.database.DBAdapter.insertSamodejne(DBAdapter.java:229)
01-30 00:56:05.232: ERROR/AndroidRuntime(731):     at edu.util.ApplicationInt.addDBSamodejne(ApplicationInt.java:49)
01-30 00:56:05.232: ERROR/AndroidRuntime(731):     at edu.xml.XMLtoDB.insertSamodejne(XMLtoDB.java:58)
01-30 00:56:05.232: ERROR/AndroidRuntime(731):     at edu.activity.SplashScreen$4.run(SplashScreen.java:97)
01-30 00:56:05.232: ERROR/AndroidRuntime(731):     at java.lang.Thread.run(Thread.java:1096)

I insert about 80 items every time I insert data, using this and similar methods:

public void addDBSplosna(SplosnaRazred s) {
      db.open();
      db.insertSplosna(s);
      db.close();  
}

DBAdapter:

   public long insertSplosna(SplosnaRazred splosna) {
        ContentValues initialValues = new ContentValues();

        initialValues.put(VREMENSKA, splosna.getVremenska());
        initialValues.put(OBETI, splosna.getObeti());
        initialValues.put(UPDATED, splosna.getServerUpdated());

        return db.insert(TABLE_SPLOS, null, initialValues);
    }

Is there a way to stop them from fighting for database? Should I lock the database until it’s done and then release it? If that’s the case, how to do it?

Answer 1

you can make method addDBSplosna(SplosnaRazred s) synchronized, to be sure that only one thread at the time can write to DB.