How to queue the same method call in Kotlin/Java

Question

I use DiffUtil to calculate for data changes in RecyclerView. The calculation is done on schedulers thread asynchronously with RxJava like below:

fun setResultItems(list: List<FlightResultItem>?) {
    Log.d("debugfilter", "            setResultItems of size: " + (list?.size?: 0))
    list?.let { newList ->
        Single.fromCallable { DiffUtil.calculateDiff(ResultItemDiffUtilCallback(ArrayList(newList), ArrayList(resultItems))) }
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe { diffResult ->
                    Log.d("debugfilter", "            setResultItems AFTER DIFF of size: " + (newList.size))
                    resultItems = ArrayList(newList)
                    diffResult.dispatchUpdatesTo(this)

                }.also { mCompositeSubscription?.add(it) }
    }
}

When the function is called consecutively, calculation of large dataset will be finished last

D: debugfilter : setResultItems of size: 113 
D: debugfilter : setResultItems of size: 7 
D: debugfilter : setResultItems AFTER DIFF of size: 7 
D: debugfilter : setResultItems AFTER DIFF of size: 113

Is there any way to queue method calls and wait for the execution to finish before executing another one?

Could using Schedulers.trampoline() work instead of IO? – Brandon Sep 03 '20 at 06:15 — Brandon, Sep 03 '20 at 06:15

score 1 · Answer 1 · answered Sep 03 '20 at 05:42

I think you can use Scheduler.single() to create a Single threaded Worker. It will process the requests Sequentially.

fun setResultItems(list: List<FlightResultItem>?) {
Log.d("debugfilter", "            setResultItems of size: " + (list?.size?: 0))
list?.let { newList ->
    Single.fromCallable { DiffUtil.calculateDiff(ResultItemDiffUtilCallback(ArrayList(newList), ArrayList(resultItems))) }
        .subscribeOn(Schedulers.single())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe { diffResult ->
            Log.d("debugfilter", "            setResultItems AFTER DIFF of size: " + (newList.size))
            resultItems = ArrayList(newList)
            diffResult.dispatchUpdatesTo(this)

        }.also { mCompositeSubscription?.add(it) }
}
}

How to queue the same method call in Kotlin/Java

1 Answers1