Issue
In my app, I use a Contacts database and display those contacts using a RecyclerView
. When I click on a contact, I want to fetch its data from the tables in the DB, and load them in a new Activity, ContactCard
. I have an AsyncTask() which fetches the PhoneNumber
objects that match the selected contactId
, but I will also need to retrieve the Address
and Email
objects from the other tables.
I would like to be able to start the activity after all the relevant data is fetched, and I tried doing this in the activity with the Contacts RecyclerView
, but the application crashes as the data has not been fetched yet.
I can call the new activity using an intent, but how can I ensure data from different tables is fetched first, before I start the new activity (which effectively displays this data)?
Some of my code:
public class PhoneNumberRepository {
private WorksideDatabase worksideDatabase;
private List<PhoneNumber> returnedNumbers;
private Context mContext;
public PhoneNumberRepository(Context context) {
String DB_NAME = "workside_database";
worksideDatabase = Room.databaseBuilder(context, WorksideDatabase.class, DB_NAME).build();
mContext = context;
}
public List<PhoneNumber> fetchPhoneNumbers(final int id) {
new AsyncTask<Integer, Void, List<PhoneNumber>>() {
@Override
protected List<PhoneNumber> doInBackground(Integer... ids) {
returnedNumbers = worksideDatabase.phoneNumberDao().getPhoneNumbersById(id);
System.out.println(returnedNumbers);
for (PhoneNumber pn : returnedNumbers) {
System.out.println("Number: " + pn.getPhoneNumber());
}
return returnedNumbers;
}
// This runs in UI when background thread finishes
@Override
protected void onPostExecute(List<PhoneNumber> result) {
super.onPostExecute(result);
System.out.println("Entered onPostExecute of fetchPhoneNumbers");
// for (PhoneNumber pn : result) {
// Toast.makeText(mContext, pn + "", Toast.LENGTH_SHORT).show();
// }
}
}.execute();
return returnedNumbers;
}
public List<PhoneNumber> getPhoneNumbers(int id) {
return fetchPhoneNumbers(id);
}
}
ContactsFragment:
adapter.setOnItemClickListener(
contact -> {
Intent viewContact = new Intent(getActivity(), WorksideContactCard.class);
viewContact.putExtra(WORKSIDE_CONTACT, contact);
PhoneNumberRepository phoneNumberRepository =
new PhoneNumberRepository(getActivity().getApplicationContext());
List<PhoneNumber> phoneNumberList;
phoneNumberList = phoneNumberRepository.getPhoneNumbers(contact.getId());
ArrayList<PhoneNumber> arrlistPhoneNumbers =
new ArrayList<>(phoneNumberList);
viewContact.putParcelableArrayListExtra(
WORKSIDE_CONTACT_PHONE_NO, arrlistPhoneNumbers);
startActivity(viewContact);
}
Solution
You can do this when you click on an item start the asyntask like this
adapter.setOnItemClickListener(
contact -> {
PhoneNumberRepository phoneNumberRepository =
new PhoneNumberRepository(getActivity().getApplicationContext());
List<PhoneNumber> phoneNumberList;
phoneNumberRepository.getPhoneNumbers(contact.getId());
}
and change your PhoneNumberRepository to this class
public class PhoneNumberRepository {
private WorksideDatabase worksideDatabase;
private List<PhoneNumber> returnedNumbers;
private Context mContext;
public PhoneNumberRepository(Context context) {
String DB_NAME = "workside_database";
worksideDatabase = Room.databaseBuilder(context, WorksideDatabase.class, DB_NAME).build();
mContext = context;
}
public void fetchPhoneNumbers(final int id) {
new AsyncTask<Integer, Void, List<PhoneNumber>>() {
@Override
protected List<PhoneNumber> doInBackground(Integer... ids) {
returnedNumbers = worksideDatabase.phoneNumberDao().getPhoneNumbersById(id);
System.out.println(returnedNumbers);
for (PhoneNumber pn : returnedNumbers) {
System.out.println("Number: " + pn.getPhoneNumber());
}
return returnedNumbers;
}
// This runs in UI when background thread finishes
@Override
protected void onPostExecute(List<PhoneNumber> result) {
super.onPostExecute(result);
Intent viewContact = new Intent(context, WorksideContactCard.class);
ArrayList<PhoneNumber> arrlistPhoneNumbers =
new ArrayList<>(result);
viewContact.putParcelableArrayListExtra(
WORKSIDE_CONTACT_PHONE_NO, arrlistPhoneNumbers);
context.startActivity(viewContact);
System.out.println("Entered onPostExecute of fetchPhoneNumbers");
}
}.execute();
}
public void getPhoneNumbers(int id) {
return fetchPhoneNumbers(id);
}
}
Answered By - Khizar Rehman
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