android - 改造 POST Realm 对象

Question

我有以下 RETROFIT API:

@POST("/payments")    
Observable<Response> saveCreditCard(@Body CreditCard creditCard)

CreditCard 是一个 RealmObject。

当我尝试使用我的 API 方法时:

CreditCard card = realm.createObject(CreditCard.class);
card.setWhateverField(...);
...
mApi.saveCreditCard(card)
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(...);

我收到以下错误:

> retrofit.RetrofitError: com.fasterxml.jackson.databind.JsonMappingException: Realm access from incorrect thread. Realm objects can only be accessed on the thread they where created.
System.err﹕ at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:400)
System.err﹕ at retrofit.RestAdapter$RestHandler.access$100(RestAdapter.java:220)
System.err﹕ at retrofit.RestAdapter$RestHandler$1.invoke(RestAdapter.java:265)
System.err﹕ at retrofit.RxSupport$2.run(RxSupport.java:55)
System.err﹕ at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:422)
System.err﹕ at java.util.concurrent.FutureTask.run(FutureTask.java:237)
System.err﹕ at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
System.err﹕ at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
System.err﹕ at retrofit.Platform$Android$2$1.run(Platform.java:142)
System.err﹕ at java.lang.Thread.run(Thread.java:818)
System.err﹕ Caused by: java.lang.AssertionError: com.fasterxml.jackson.databind.JsonMappingException: Realm access from incorrect thread. Realm objects can only be accessed on the thread they where created.

我假设 RETROFIT 正在 io() 调度程序上对 JSON 进行序列化，因此出现错误。

有没有人对我如何克服 Realm 的线程问题有任何建议？

Answer 1

更新

Realm 添加了对使用 realm.copyFromRealm(yourObject, depthLevel) 分离对象的支持

CreditCard creditCard = realm.createObject(CreditCard.class);
card.setWhateverField(...);
...

final int relationshipsDepthLevel = 0;
creditCard = realm.copyFromRealm(creditCard, relationshipsDepthLevel);
mApi.saveCreditCard(temporaryCard)
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(...);

弃用的答案如下:

我找到了一个解决方法，它需要 2 行额外的代码和一个额外的序列化步骤。

@Inject
ObjectMapper mObjectMapper; // I use Dagger2 for DI

....

CreditCard creditCard = realm.createObject(CreditCard.class);
card.setWhateverField(...);
...
// I use Jackson's ObjectMapper to "copy" the original creditCard
// to a new temporary instance that has not been tied to a Realm.
String json = mObjectMapper.writeValueAsString(creditCard);
PaymentCreditCardDataView temporaryCard = mObjectMapper
                    .reader(PaymentCreditCardDataView.class)
                    .readValue(json);
mApi.saveCreditCard(temporaryCard)
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(...);

缺点是我在 UI 线程上有一个额外的对象和一个额外的序列化+反序列化步骤。如果我有尺寸合理的物体应该没问题。