Extract SQLBrite logic to external class in Android

Question

In my chat app I use SQLBrite wrapper to update chat from local database. Currently my activity holds both UI and SQLBrite. Now I want to extract SQLBrite logic to external class. So while my activity is living I need my extracted SQLBrite also be alive. Currently I have problem with subscriber. I also extracted it to external class, and its emitting query all the time, event though everything is same as it was while it was in activity, and it was working.

this is old code, where everything was in same activity: How I can do this?

SqlBrite sqlBrite;
sqlBrite = SqlBrite.create(DatabaseManager.DatabaseHelper);
private final CompositeSubscription subscriptions = new CompositeSubscription();

private void saveMessage(Message message) {

        ContentValues values = new ContentValues();
        values.put(DatabaseContract.MessageEntry.COLUMN_NAME_MESSAGE_ID, message.getId());
        values.put(DatabaseContract.MessageEntry.COLUMN_NAME_SERIAL_NUMBER, message.getSerialNumber());
        values.put(DatabaseContract.MessageEntry.COLUMN_NAME_TEXT, message.getText());

        sqlBrite.insert(DatabaseContract.MessageEntry.TABLE_NAME, values, SQLiteDatabase.CONFLICT_IGNORE);
    }

    private void subscribeToDbChanges() {
        String NEW_MSG_QUERY = "SELECT * FROM "
                + DatabaseContract.MessageEntry.TABLE_NAME
                + " WHERE "
                + DatabaseContract.MessageEntry.COLUMN_NAME_CREATED_AT_MILLS
                + " >= ? ORDER BY "
                + DatabaseContract.MessageEntry.COLUMN_NAME_CREATED_AT_MILLS
                + " DESC";

        String grpId = String.valueOf(groupId);
        String msgDate = String.valueOf(dividerMsgDate);

        Observable<Query> freshMessages = sqlBrite.createQuery(DatabaseContract.MessageEntry.TABLE_NAME, NEW_MSG_QUERY, grpId, msgDate);
        subscriptions.add(
                freshMessages.subscribe(query -> parseQueryData(query)));
    }

    private void parseQueryData(Query query) {
        Log.d(TAG, "subscriber called");
        List<Message> messages = new ArrayList<>();
        Cursor c = query.run();
        try {
            while (c.moveToNext()) {
                Message message = new Message();
                message.setLocalId(c.getInt(c.getColumnIndexOrThrow(DatabaseContract.MessageEntry._ID)));
                message.setId(c.getInt(c.getColumnIndexOrThrow(DatabaseContract.MessageEntry.COLUMN_NAME_MESSAGE_ID)));

                messages.add(message);
            }
        } finally {
            c.close();
        }

        updateChatList(messages, "new");
    }

Answer 1

I am not 100% sure I understood your question, but I would create a SQLBrite Helper class with the code you provided above and instantiate it in the onCreate() of the activity.

Additionally you have to pass the onResume() and onPause() events to your helper class (because you only need it when the activity is active), and return the results via a Callback.

 MyActivity.java


 public class MyActivity extends Activity implements SQLHelper.ResultListener {

   SQLHelper mSQLHelper;

   public void onCreate() {
     mSQLHelper = new SQLHelper(this);
   }


   public void onResume() {
     mSQLHelper.onResume();
   }


   public void onPause() {
     mSQLHelper.onPause();
   }

   @
   Override
   public void onUpdateChatList(String _message) {
     //show it
   }
 }


 SQLHelper.java

 public class SQLHelper {

   ResultListener mListener;

   public interface ResultListener {
     public void onUpdateChatList(String _message);
   }

   public void SQLHelper(ResultListener _resultListener) {
     mListener = _resultListener;
   }


   public void onResume() {
     //Here subscribe to your query
   }


   public void onPause() {
     //here unsubscribe
   }

   private void parseQueryData(Query query) {
     //... your code
     mListener.onUpdateChatList(String _message);
   }
 }

Hope that helps.