Sharing data between Runnable and Activity

Question

In my main activity I start an AlarmManager. The Intent of this AlarmManager is a class which extends BroadcastReceiver. Now, in this BroadcastReceiver class I execute an AsyncTask in the onReceive() method. The doInBackground() method of this AsyncTask calls a method which starts a new instance of a Runnable. And in the run() method of this Runnable I do some data polling and save the data to SharedPreference and/or an SQLiteDatabase.

Back in my main activity I want to know these values that have been read and saved. This works fine for some values. I read by using SharedPreferences and/or the SQLiteDatabase.

I can see that when one value changes (the polling thread is reading values that change every 5 minutes, the correct value is stored in the database, but when I read it afterwards in the main activity I just get the old value.

Here's an example of what I do:

I have a helper class called Util. This is called from the run() method:

Util.storeT1(db, <float value>);

Here's the method:

public static void storeT1(DBAdapter db, float value) {
    db.open();
    long id = 0;
    id = db.insertFloat("T1", value);
    if (id == -1) { // if error
    }
    db.close();     
}

In the main activity, I do:

float val = Util.getT1(db);

Here's the method:

public static float getT1(DBAdapter db) {
    float i = 0;
    db.open();
    Cursor c = db.get("T1");
    if (c.moveToFirst()) {
        do {
            i = c.getFloat(0);
        } while (c.moveToNext());
    }
    c.close();
    db.close();
    return i;
}

In the above, db is an instance of my DBAdapter class, which is a class handling the database. Relevant methods:

public Cursor get(String column) throws SQLException {
    Cursor mCursor = db.query(DATABASE_TABLE, new String[] { column },
            null, null, null, null, null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;
}

public long insertFloat(String key, Float value) {
    ContentValues initialValues = new ContentValues();
    initialValues.put(key, value);
    return db.insert(DATABASE_TABLE, null, initialValues);
}

So, how do I share data correctly between the Runnable and my Activity? I have a feeling it's because of the multiple threads, but I don't know how to fix this.

Edit:

I should mention that when I do this:

float val = Util.getT1(db);

I get the value 0.0, not the value saved from the Runnable.