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I am using live data to update some view of the activity. the view contain question numbers both total question number and answered question number eg: 2/10 (answered/total) the questions can be filtered using actors, if no actor is selected then it will list all questions (consider the total questions number as 100) then if I am selecting any actor(like a developer, HR) then the questions total number is reduced to another value something less than 100 (like 20 ) the total count is returned using the dao method

 @Query("SELECT COUNT(actor) FROM questions WHERE actor IN (:actors)")
    LiveData<Integer> getNumberOfQuestions(String[] actors);

here String[] actors is the selected actor list

Using an observer

questionsViewModel.getTotalQuestionCount(mCheckedActorList).observe(this, new Observer<Integer>() {
            @Override
            public void onChanged(@Nullable Integer countTotal) {
                if (countTotal != null)
                    mTotalCount = String.valueOf(countTotal);
                if (mAnswerCount != null && mTotalCount != null)
                    mAllQuestionAnswered.setText(mAnswerCount.concat("/").concat(mTotalCount));

            }
        });

I am observing the count, but consider the scenario

  1. no filter applied (no actor selected,count =100)
  2. actor developer is selected (count = 20)

onchanged in the first case returns 100 and in second it returns 100 and 20 I only want the current value, ie 20 how can solve this? what am I doing wrong?

enter image description here

in view model

 public LiveData<Integer> getTotalQuestionCount(List<String> actorsList) {
        if (actorsList != null && actorsList.size() > 0) {
            String[] actorArray = new String[actorsList.size()];
            actorArray = actorsList.toArray(actorArray);
            return questionsRepository.getTotalCount(actorArray);

        } else {
            return questionsRepository.getTotalCount();
        }
    }
MarGin
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  • How is specified `questionsRepository.getTotalCount()` method in dao ? Are you using same method again, when all questions needed ? – blackkara Feb 27 '19 at 09:42
  • no there another method @Query("SELECT COUNT(actor) FROM questions") LiveData getNumberOfQuestions(); – MarGin Feb 27 '19 at 09:58

2 Answers2

1

It's hard to know whole scenario but a few things in my mind about this

When you make new request with actor change, you doubling(and possibly more) live requests.

So as a result,

  • A live query is for all values
  • A live query is values for specified actors
  • And possible other live queries

Before making new live request you can clear the previous one, or you can use List instead of LiveData.

Sample usage for clearing the observer of live query,

Hold the LiveData and Observer 

Observer<Integer> observerOfLiveQuery = new Observer<Integer>() {
    @Override
    public void onChanged(@Nullable Integer countTotal) {
        if (countTotal != null)
            mTotalCount = String.valueOf(countTotal);
        if (mAnswerCount != null && mTotalCount != null)
            mAllQuestionAnswered.setText(mAnswerCount.concat("/").concat(mTotalCount));
    }
}

LiveData<Intener> firstLiveQuery = getTotalQuestionCount(...)
firstLiveQuery.observe(this, observerOfLiveQuery)

LiveData<Intener> secondLiveQuery = getTotalQuestionCount(...)
firstLiveQuery.removeObserver(observerOfLiveQuery)
secondLiveQuery.observe(this, observerOfLiveQuery)
blackkara
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  • Updated the answer. – blackkara Feb 27 '19 at 11:09
  • I actually tried something similar to this but this doesn't seem to work if (questionsViewModel != null && questionsViewModel.getTotalQuestionCount(mCheckedActorList).hasActiveObservers()) questionsViewModel.getTotalQuestionCount(mCheckedActorList).removeObservers(this); – MarGin Feb 27 '19 at 11:18
  • Instead of calling like this `getTotalQuestionCount(...).hasActiveObservers())`, hold the live data in a variable `firstLiveQuery = getTotalQuestionCount(...)`, then use `hasActiveObservers()` via the variable. – blackkara Feb 27 '19 at 11:24
0

Just call

questionsViewModel.getTotalQuestionCount(mCheckedActorList).setValue(null)

before calling view model this will clear the previous value

Syscall
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Sharjeel Ahmad Siddiqui
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