observable的.subscribeOn(Schedulers.io())方法是指定處理的事件流在哪個執行緒中執行
Schedulers：對外提供獲取的方法
IOTask：統一task的建立方式
Scheduler:統一呼叫的api，IoScheduler/ComputationScheduler/NewThreadScheduler均為繼承類。
Scheduler.Worker：管理具體執行的任務。
1， 改用該方法後，建立了ObservableSubscribeOn物件，將上層的observable進行包裝代理和傳入的Scheduler進行儲存。
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.CUSTOM)
public final Observable<T> subscribeOn(Scheduler scheduler) {
ObjectHelper.requireNonNull(scheduler, "scheduler is null");
return RxJavaPlugins.onAssembly(new ObservableSubscribeOn<T>(this, scheduler));
}
複製程式碼2， 然後會執行到ObservableSubscribeOn的subscribeActual方法，在（1）中的時候寫過這個流程。在這個方法中，核心程式碼是第三句。
public final class ObservableSubscribeOn<T> extends AbstractObservableWithUpstream<T, T> {
final Scheduler scheduler;
public ObservableSubscribeOn(ObservableSource<T> source, Scheduler scheduler) {
super(source);
this.scheduler = scheduler;
}
@Override
public void subscribeActual(final Observer<? super T> s) {
final SubscribeOnObserver<T> parent = new SubscribeOnObserver<T>(s);
s.onSubscribe(parent);
parent.setDisposable(scheduler.scheduleDirect(new SubscribeTask(parent)));
}
複製程式碼3,
parent.setDisposable(scheduler.scheduleDirect(new SubscribeTask(parent)));
在這行語句中 scheduler是處理runable的執行緒池,就是傳過來的Schedulers.io()物件。 SubscribeTask是個Runnable
執行緒池執行runable的run方法。 source是上層的observable parent是對下層包裝的observer
final class SubscribeTask implements Runnable {
private final SubscribeOnObserver<T> parent;
SubscribeTask(SubscribeOnObserver<T> parent) {
this.parent = parent;
}
public void run() {
source.subscribe(parent);
}
}
}
複製程式碼最終的結果會呼叫到SubscribeOnObserver的onNext中。
static final class SubscribeOnObserver<T> extends AtomicReference<Disposable> implements Observer<T>, Disposable {
final Observer<? super T> actual;
final AtomicReference<Disposable> s;
SubscribeOnObserver(Observer<? super T> actual) {
this.actual = actual;
this.s = new AtomicReference<Disposable>();
}
@Override
public void onNext(T t) {
actual.onNext(t);
}
}
複製程式碼4， Schedulers.io()的準備工作
IO 的賦值的是在靜態程式碼塊中初始化。
public static Scheduler io() {
return RxJavaPlugins.onIoScheduler(IO);
}
static {
// 通過這個方法 呼叫 IOTask中的call 返回 new IoScheduler() 物件
IO = RxJavaPlugins.initIoScheduler(new IOTask());
}
複製程式碼5， IoScheduler繼承Scheduler。並且實現了Scheduler的抽象方法createWorker。
@NonNull
public Disposable scheduleDirect(@NonNull Runnable run) {
return scheduleDirect(run, 0L, TimeUnit.NANOSECONDS);
}
@NonNull
public Disposable scheduleDirect(@NonNull Runnable run, long delay, @NonNull TimeUnit unit) {
final Worker w = createWorker();
final Runnable decoratedRun = RxJavaPlugins.onSchedule(run);
DisposeTask task = new DisposeTask(decoratedRun, w);
w.schedule(task, delay, unit);
return task;
}
複製程式碼6, 在 IoScheduler的createWorker方法中建立了EventLoopWorker物件。所以在w.schedule是呼叫的EventLoopWorker中的schedule方法。
@Override
public Worker createWorker() {
return new EventLoopWorker(pool.get());
}
複製程式碼 static final class EventLoopWorker extends Scheduler.Worker {
private final CompositeDisposable tasks;
private final CachedWorkerPool pool;
private final ThreadWorker threadWorker;
EventLoopWorker(CachedWorkerPool pool) {
this.pool = pool;
this.tasks = new CompositeDisposable();
this.threadWorker = pool.get();
}
@Override
public Disposable schedule(@NonNull Runnable action, long delayTime, @NonNull TimeUnit unit) {
if (tasks.isDisposed()) {
return EmptyDisposable.INSTANCE;
}
return threadWorker.scheduleActual(action, delayTime, unit, tasks);
}
}
複製程式碼7， ThreadWorker執行緒工作類，繼承NewThreadWorker，scheduleActual在NewThreadWorker中。
static final class ThreadWorker extends NewThreadWorker {
private long expirationTime;
ThreadWorker(ThreadFactory threadFactory) {
super(threadFactory);
this.expirationTime = 0L;
}
public long getExpirationTime() {
return expirationTime;
}
public void setExpirationTime(long expirationTime) {
this.expirationTime = expirationTime;
}
}
複製程式碼8， 在這裡看到executor.schedule，呼叫執行緒池執行runable的地方。runable方法一直傳遞到這裡。
@NonNull
public ScheduledRunnable scheduleActual(final Runnable run, long delayTime, @NonNull TimeUnit unit, @Nullable DisposableContainer parent) {
Runnable decoratedRun = RxJavaPlugins.onSchedule(run);
ScheduledRunnable sr = new ScheduledRunnable(decoratedRun, parent);
if (parent != null) {
if (!parent.add(sr)) {
return sr;
}
}
Future<?> f;
try {
if (delayTime <= 0) {
f = executor.submit((Callable<Object>)sr);
} else {
f = executor.schedule((Callable<Object>)sr, delayTime, unit);
}
sr.setFuture(f);
} catch (RejectedExecutionException ex) {
if (parent != null) {
parent.remove(sr);
}
RxJavaPlugins.onError(ex);
}
return sr;
}
複製程式碼類圖
