public boolean databaseLoaded(Context context)  {
    File dbFile = context.getDatabasePath(MyConstants.DEFAULT_DATABASE);
    return dbFile.exists();
}

class DatabaseHelper extends SQLiteAssetHelper {

    public DatabaseHelper(Context context, String databaseName, int databaseVersion) {
        super(context, databaseName, null, databaseVersion);
        if (databaseVersion>1 && databaseName.equals(MyConstants.DEFAULT_DATABASE)) {
            setForcedUpgradeVersion(databaseVersion);
        }
    }
}

@Override
public boolean onCreate() {


    DATABASE = constants.getDBName();
    db=new DatabaseHelper(getContext(), DATABASE, MyConstants.DATABASE_VERSION);
    return((db == null) ? false : true);
}

@Override
public Cursor query(Uri url, String[] projection, String selection, String[] selectionArgs, String sort) {

    /**if updating the app, pause to wait for the database to transfer**/
    SharedPreferences sharedPreferences = getContext().getSharedPreferences(MyConstants.PREFS, 0);
    int lastDBVersion = sharedPreferences.getInt("db_version", MyConstants.STARTING_DB_VERSION);
    if (lastDBVersion<MyConstants.DATABASE_VERSION)  {
        try {
            Thread.sleep(5000);
        } catch(InterruptedException ex) {
            Thread.currentThread().interrupt();
        }
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putInt("db_version", MyConstants.DATABASE_VERSION);
        editor.commit();
    }

    SQLiteQueryBuilder qb=new SQLiteQueryBuilder();

    qb.setTables(TABLE);

    String orderBy;

    if (TextUtils.isEmpty(sort)) {
      orderBy=_ID;
    }
    else {
      orderBy=sort;
    }
    Cursor c= null;
    if (db.getReadableDatabase()!=null) {
        c= qb.query(db.getReadableDatabase(), projection, selection,
                 selectionArgs, null, null, orderBy);
        c.setNotificationUri(getContext().getContentResolver(), url);
    }
    return c;
}

java.lang.RuntimeException: An error occured while executing doInBackground()
    at android.os.AsyncTask$3.done(AsyncTask.java:300)
    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
    at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
    at java.util.concurrent.FutureTask.run(FutureTask.java:242)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
    at java.lang.Thread.run(Thread.java:841)
    Caused by: java.lang.NullPointerException
    at     com.readystatesoftware.sqliteasset.SQLiteAssetHelper.getWritableDatabase(SQLiteAssetHelper.java:180)  //this is where db.getVersion() is null
    at com.readystatesoftware.sqliteasset.SQLiteAssetHelper.getReadableDatabase(SQLiteAssetHelper.java:257)
    at com.mypackage.Provider.query(Provider.java:84)  //this is if (db.getReadableDatabase()!=null) {...
    at android.content.ContentProvider.query(ContentProvider.java:857)
    at android.content.ContentProvider$Transport.query(ContentProvider.java:200)
    at android.content.ContentResolver.query(ContentResolver.java:477)
    at android.content.ContentResolver.query(ContentResolver.java:420)
    at com.mypackage.MyClass$MyMethod.doInBackground(MyClass.java:594)  //This is Cursor c = getActivity().getContentResolver().query...
    at com.mypackage.MyClass$MyMethod.doInBackground(MyClass.java:1)
    at android.os.AsyncTask$2.call(AsyncTask.java:288)
    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
    ... 4 more
    java.lang.NullPointerException
    at   com.readystatesoftware.sqliteasset.SQLiteAssetHelper.getWritableDatabase(SQLiteAssetHelper.java:180)
    at com.readystatesoftware.sqliteasset.SQLiteAssetHelper.getReadableDatabase(SQLiteAssetHelper.java:257)
    at com.mypackage.Provider.query(Provider.java:84)
    at android.content.ContentProvider.query(ContentProvider.java:857)
    at android.content.ContentProvider$Transport.query(ContentProvider.java:200)
    at android.content.ContentResolver.query(ContentResolver.java:477)
    at android.content.ContentResolver.query(ContentResolver.java:420)
    at com.mypackage.MyClass$MyMethod.doInBackground(MyClass.java:594)
    at com.mypackage.MyClass$MyMethod.doInBackground(MyClass.java:1)
    at android.os.AsyncTask$2.call(AsyncTask.java:288)
    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
    at java.lang.Thread.run(Thread.java:841)