RxKotlin - 错误的 subscribeOn，observeOn 线程更改 Activity 中的主题？

Question

我有一个在随机时刻生成不同字符串的对象，我需要订阅这个生成器以获取这些字符串并将它们提供给 ui（也许它会是不同的多个订阅者活动）。假设，我得到以下代码：

发电机：

class Generator {

    private var stringToGenerate = ""

    var subject: BehaviorSubject<String> = BehaviorSubject.create<String>()

    init {
        //seems like these instructions are skipped
        subject
                .subscribeOn(AndroidSchedulers.mainThread())
                .doOnNext { t -> Log.i("subject doOnNext", Thread.currentThread().name + " " + Thread.currentThread().id) }
                .observeOn(AndroidSchedulers.mainThread())
                .map { _ -> Log.i("subject map", Thread.currentThread().name + " " + Thread.currentThread().id) }

        //imitation of async creating of strings in separate thread
        timer("timerThread", false, 2000L, 2000L) {
            stringToGenerate = System.currentTimeMillis().toString()
            subject.onNext(stringToGenerate)
        }
    }
}

必须使用生成的字符串的活动之一：

class TestActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_test)

        val wrongThreadObserver = object : Observer<String> {
            override fun onComplete() {
            }

            override fun onSubscribe(d: Disposable) {
            }

            override fun onNext(t: String) {
                Log.i("wrongThreadObserver", Thread.currentThread().name + " " + Thread.currentThread().id)
            }

            override fun onError(e: Throwable) {
            }
        }

        val generator = Generator()
        generator.subject.subscribe(wrongThreadObserver)

        //for correct work illustration
        val correctThreadObserver = object : Observer<String> {
            override fun onComplete() {
            }

            override fun onSubscribe(d: Disposable) {
            }

            override fun onNext(t: String) {
                Log.i("correctThreadObserver", Thread.currentThread().name + " " + Thread.currentThread().id)
            }

            override fun onError(e: Throwable) {
            }
        }

        val mainThreadSubject = BehaviorSubject.create<String>()
        mainThreadSubject
                .doOnNext { obj -> Log.i("correctThread doOnNext", Thread.currentThread().name + " " + Thread.currentThread().id) }
                .subscribeOn(Schedulers.io())
                .observeOn(Schedulers.newThread())
                .subscribe(correctThreadObserver)
        mainThreadSubject.onNext("test thread")
        val handler = Handler()
        handler.postDelayed({ mainThreadSubject.onNext("test thread 2") }, 1000)
        handler.postDelayed({ mainThreadSubject.onNext("test thread 3") }, 2000)
    }
}

在这种情况下 correctThreadObserver，刚在 activity 中创建，工作正常，但 wrongThreadObserver 继续在计时器线程中工作，它似乎忽略了 Generator 中的指令 subscribeOn、ObserveOn、doOnNext，无论这些指令在哪里调用 - 在 init 中，在计时器线程中，在 activity 中通过从生成器 - wrongThreadObserver 仍在计时器线程中工作。所以日志是：

I/correctThread doOnNext: main 2

I/correctThreadObserver: RxNewThreadScheduler-1 941

I/correctThread doOnNext: main 2

I/correctThreadObserver: RxNewThreadScheduler-1 941

I/wrongThreadObserver: timerThread 937

I/correctThread doOnNext: main 2

I/correctThreadObserver: RxNewThreadScheduler-1 941

I/wrongThreadObserver: timerThread 937

I/wrongThreadObserver: timerThread 937

I/wrongThreadObserver: timerThread 937

没有 doOnNext 并且 wrongThreadObserver 没有主线程我做错了什么？

Answer 1

我找到以下解决方案：我们必须订阅 Observable，而不是 Subject，所以我们必须使用方法 observeOn() 的结果，而不是对象 "subject" 本身。如果需要多次订阅，我们可以将 observeOn 的结果缓存在单独的变量中：

//in Generator
.......
var observableInSeparateVar = subject.observeOn(AndroidSchedulers.mainThread())
.......

//in TestActivity
.......
generator.observableInSeparateVar.subscribe(wrongThreadObserver)
.......

我们也可以调用observeOn()进行主题订阅：

//in TestActivity
.......
generator.subject
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(wrongThreadObserver)

RxKotlin - 错误的 subscribeOn，observeOn 线程更改 Activity 中的主题？

RxKotlin - Wrong subscribeOn, observeOn thread changing for Subject out of Activity?

multithreading

android

rx-kotlin

kotlin-android-extensions

rx-kotlin2