Nrthugu

I'm getting this type of error:

Fatal Exception: java.lang.IllegalStateException: Cannot create asynchronous query while in a write transaction in /Users/cm/Realm/realm-java/realm/realm-library/src/main/cpp/io_realm_internal_OsResults.cpp line 252

       at io.realm.internal.OsResults.nativeStartListening(OsResults.java)

       at io.realm.internal.OsResults.addListener(OsResults.java:405)

       at io.realm.internal.OsResults.addListener(OsResults.java:412)

       at io.realm.RealmResults.addChangeListener(RealmResults.java:173)

       at io.realm.internal.ObservableCollection$RealmChangeListenerWrapper.onChange(ObservableCollection.java:39)

       at io.realm.internal.ObservableCollection$CollectionObserverPair.onChange(ObservableCollection.java:20)

       at io.realm.internal.ObservableCollection$Callback.onCalled(ObservableCollection.java:64)

       at io.realm.internal.ObservableCollection$Callback.onCalled(ObservableCollection.java:54)

       at io.realm.internal.ObserverPairList.foreach(ObserverPairList.java:109)

       at io.realm.internal.OsResults.notifyChangeListeners(OsResults.java:451)

       at io.realm.internal.OsSharedRealm.nativeBeginTransaction(OsSharedRealm.java)

       at io.realm.internal.OsSharedRealm.beginTransaction(OsSharedRealm.java:269)

       at io.realm.BaseRealm.beginTransaction(BaseRealm.java:401)

       at io.realm.Realm.beginTransaction(Realm.java:146)

How can I make sure that I'm not in transaction while I am adding addChangeListeners? A simple approach of mRealm.isInTransaction could help or the problem is in codes structure?

public void update() {

    sData = dataQuery.sort(Data.ORDER, Sort.ASCENDING).findAllAsync();

    sData.addChangeListener(new RealmChangeListener<RealmResults<Data>>() {

        @Override

        public void onChange(RealmResults<Data> element) {

            sDiffData = mRealm.where(DiffData.class)

                    .greaterThanOrEqualTo(...)

                    .lessThan(...)

                    .equalTo(..)

                    .findAllAsync();

            sDiffData.addChangeListener(new RealmChangeListener<RealmResults<...>>() {

                @Override

                public void onChange(RealmResults<...> element) {

                    ...

            });

        }

    });

}

I cannot re-produce error myself, but I can see it in crashlytics showing up pretty often.

This happens if you have a UI-thread write transaction and also have a RealmChangeListener in which you also execute an async query (or addChangeListener).

Solution 1: don't use UI thread write transactions because they can potentially block your UI and your app will be slow and bad

Solution 2: if you're in a write transaction inside the RealmChangeListener, then execute the logic in a handler.post { block

private void fetchDiff() {

        sDiffData = mRealm.where(DiffData.class)

                .greaterThanOrEqualTo(...)

                .lessThan(...)

                .equalTo(..)

                .findAllAsync();

        sDiffData.addChangeListener(new RealmChangeListener<RealmResults<...>>() {

            @Override

            public void onChange(RealmResults<...> element) {

                ...

        });

}



public void update() {

    sData = dataQuery.sort(Data.ORDER, Sort.ASCENDING).findAllAsync();

    sData.addChangeListener(new RealmChangeListener<RealmResults<Data>>() {

        @Override

        public void onChange(RealmResults<Data> element) {

            Realm realm = element.getRealm();

            if(realm.isInTransaction()) {

                handler.post(() -> {

                    fetchDiff();

                });

            } else {

                fetchDiff();

            }

        }

    });

}