域在使用多个addChangeListeners时“不能创建异步查询”

Question

我得到了这类错误：

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)

当我添加addChangeListeners时，如何确保我没有处于事务处理中？一个简单的mRealm.isInTransaction方法可以帮助还是问题是在代码结构？

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) {
                    ...
            });
        }
    });
}

我自己不能再犯错误，但我可以在“破折号”中看到它经常出现。

Answer 1

如果您有一个UI线程写入事务，并且有一个RealmChangeListener，在其中还执行一个异步查询(或addChangeListener)，就会发生这种情况。

解决方案1:不要使用UI线程写入事务，因为它们可能会阻塞您的UI，并且您的应用程序会慢而坏

解决方案2:如果您在RealmChangeListener内部的写事务中，那么在handler.post {块中执行逻辑

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();
            }
        }
    });
}