Unable to delete table from room database

Question

I have implemented Room Persistence Library in my App. Using this i'm 1.Adding data to a table 2.Displaying it 3.Deleting table Im Doing these three steps In a loop. But Problem here is Table content gets deleted only after restart the app. Means table data wont get deleted until i restart the app. My code is here

Adding,Reading,Displaying Database table

public void DatabaseTask{
for(getting data from web server){
//Adding them to database
 AddToDatabase addToDatabase=new AddToDatabase(file.getId(),file.getName(),"punith@gmail.com");
                addToDatabase.execute();
}
//Reading Table from Database
  ReadFromDatabase readFromDatabase=new ReadFromDatabase();
            readFromDatabase.execute();
//Deleting table from database
  DeleteFromDatabase deleteFromDatabase=new DeleteFromDatabase();
            deleteFromDatabase.execute();

}
This DatabaseTask class will be executed every 15 minutes

Asynch Task Class for Adding,Reading,Deleting

 private class AddToDatabase extends AsyncTask<String,String,String>{
      String id;
      String name,email;
        public AddToDatabase(String id,String name, String email){
            this.id=id;
            this.name=name;
            this.email=email;

      }
        @Override
        protected String doInBackground(String... strings) {
            User user=new User();
            user.setId(id);
            user.setName(name);
            user.setEmail(email);
            MainActivity.myAppDatabase.myDao().addUser(user);
            return null;
        }

        @Override
        protected void onPostExecute(String s) {
            Log.d("mPavan001", "add done");
            super.onPostExecute(s);
        }
    }
    private class ReadFromDatabase extends AsyncTask<String,String,String>{

        @Override
        protected String doInBackground(String... strings) {

            List<User> users=MainActivity.myAppDatabase.myDao().getUsers();
            for(User usr: users){
                String id=usr.getId();
                String name=usr.getName();
                String email=usr.getEmail();
                 info=info+"\n\n"+"id :"+id+"\n Name :"+name+"\n Email :"+email;
            }
            return null;
        }

        @Override
        protected void onPostExecute(String s) {
            Log.d("mPavan001", "onPostExecute: "+info);
            super.onPostExecute(s);
        }
    }
    private class DeleteFromDatabase extends AsyncTask<String,String,String>{

        @Override
        protected String doInBackground(String... strings) {

            MainActivity.myAppDatabase.myDao().deleteAll();

            return null;
        }

        @Override
        protected void onPostExecute(String s) {
            Log.d("mPavan001", "delete done");
            super.onPostExecute(s);
        }
    }

data access object

@Dao
public interface MyDao {

    @Insert
    public void addUser(User user);

    @Query("select * from users")
    public List<User> getUsers();

    @Query("DELETE FROM users")
    public void deleteAll();
}

How can i resolve this issue? Please ask if you need more details.

Answer 1

It looks like you are just deleting data, without listening for its changes.

Consider getting data from database using LiveData , and observing LiveData in your Fragment or Activity . That way your view will be always aware of data changes.

One more thing is that you probably are checking for data changes manually after deleting it. If so: please post your code for that block.

Answer 2

I did a silly mistake , I was using info string to display the database table value. but I was not setting it to null on every loop iteration. So it used to store data from previous loop iteration as well , Even though the database table was getting deleted!