在Android RxLife 一款轻量级别的RxJava生命周期管理库（一）一文中，我们讲解了lift,compose这两个操作符的使用，及RxJava是如何造成内存泄漏的，RxLife又是如何解决RxJava内存泄漏的。在这不再次进行讲解，如果还没有看的，请回头阅读
本文主要讲解RxLife在最新版本1.0.4中的as操作符的使用及其作用。
gradle依赖
implementation 'com.rxjava.rxlife:rxlife:1.0.4'源码下载 欢迎star
看过上篇文章的同学知道，在使用lift,compose这两个操作符时，我们规定了下游除了subscribe操作符外不能有其它的操作符出现，然后这种规定不是代码层面的规定，需要开发者在开发时额外注意，显然这种方案是不完美的，那么我们能不能从代码层面上去规定呢？此时就要请我们主角出场了！
as操作符
我们先来看看as操作符如何使用。(以下代码默认运行在Activity中)
Observable.intervalRange(1, 100, 0, 200, TimeUnit.MILLISECONDS)
.as(RxLife.as(this)) //this 为LifecycleOwner对象
.subscribe(aLong -> {
Log.e("LJX", "accept=" + aLong);
});这样就可以了？是的，就这么简单。那么as 是如何规避下游不会出现除subscribe之外的操作符呢？我们先来看看使用as操作符，返回的啥？
ObservableLife observableLife = Observable
.intervalRange(1, 100, 0, 200, TimeUnit.MILLISECONDS)
.as(RxLife.asOnMain(this)); 返回的是一个ObservableLife对象，这是什么鬼？进去看看
/**
* User: ljx
* Date: 2019/4/18
* Time: 18:40
*/
public class ObservableLife extends RxSource> {
private Observable upStream;
ObservableLife(Observable upStream, LifecycleOwner owner, Event event, boolean onMain) {
super(owner, event, onMain);
this.upStream = upStream;
}
@Override
public final Disposable subscribe() {
return subscribe(Functions.emptyConsumer(), Functions.ON_ERROR_MISSING, Functions.EMPTY_ACTION, Functions.emptyConsumer());
}
public final Disposable subscribe(Consumer onNext) {
return subscribe(onNext, Functions.ON_ERROR_MISSING, Functions.EMPTY_ACTION, Functions.emptyConsumer());
}
public final Disposable subscribe(Consumer onNext, Consumer onError) {
return subscribe(onNext, onError, Functions.EMPTY_ACTION, Functions.emptyConsumer());
}
public final Disposable subscribe(Consumer onNext, Consumer onError,
Action onComplete) {
return subscribe(onNext, onError, onComplete, Functions.emptyConsumer());
}
public final Disposable subscribe(Consumer onNext, Consumer onError,
Action onComplete, Consumer onSubscribe) {
ObjectHelper.requireNonNull(onNext, "onNext is null");
ObjectHelper.requireNonNull(onError, "onError is null");
ObjectHelper.requireNonNull(onComplete, "onComplete is null");
ObjectHelper.requireNonNull(onSubscribe, "onSubscribe is null");
LambdaObserver ls = new LambdaObserver(onNext, onError, onComplete, onSubscribe);
subscribe(ls);
return ls;
}
@Override
public final void subscribe(Observer observer) {
ObjectHelper.requireNonNull(observer, "observer is null");
try {
observer = RxJavaPlugins.onSubscribe(upStream, observer);
ObjectHelper.requireNonNull(observer, "The RxJavaPlugins.onSubscribe hook returned a null Observer. Please change the handler provided to RxJavaPlugins.setOnObservableSubscribe for invalid null returns. Further reading: https://github.com/ReactiveX/RxJava/wiki/Plugins");
subscribeActual(observer);
} catch (NullPointerException e) { // NOPMD
throw e;
} catch (Throwable e) {
Exceptions.throwIfFatal(e);
// can't call onError because no way to know if a Disposable has been set or not
// can't call onSubscribe because the call might have set a Subscription already
RxJavaPlugins.onError(e);
NullPointerException npe = new NullPointerException("Actually not, but can't throw other exceptions due to RS");
npe.initCause(e);
throw npe;
}
}
private void subscribeActual(Observer observer) {
Observable upStream = this.upStream;
if (onMain) {
upStream = upStream.observeOn(AndroidSchedulers.mainThread());
}
upStream.onTerminateDetach().subscribe(new LifeObserver<>(observer, owner, event));
}
} 仔细的你会发现，ObservableLife类里面就只有一系列的subscribe方法，而且跟Observable里面的subscribe方法是一一对应的，功能也是一样的。到这，我们就明白了，原来as操作符返回的是一个自定义的对象，而且该对象只提供了一系列subscribe方法，这样就规避了下游不会再出现其它的操作符，就避免内存泄漏等危险。
到这，as操作符的原理我们就讲清楚了，我们再来看看as操作符的其它用法。
指定生命周期关闭管道
Observable.intervalRange(1, 100, 0, 200, TimeUnit.MILLISECONDS)
//指定在onStop关闭管道，也可以指定其它生命周期，不指定默认在onDestroy关闭管道
.as(RxLife.as(this, Event.ON_STOP))
.subscribe(aLong -> {
Log.e("LJX", "accept=" + aLong + " Thread=" + Thread.currentThread());
});指定观察者在主线程回调
Observable.intervalRange(1, 100, 0, 200, TimeUnit.MILLISECONDS)
.as(RxLife.asOnMain(this)) //asOnMain即代表在主线程回调
.subscribe(aLong -> {
Log.e("LJX", "accept=" + aLong + " Thread=" + Thread.currentThread());
});
//等价于
Observable.intervalRange(1, 100, 0, 200, TimeUnit.MILLISECONDS)
.observeOn(AndroidSchedulers.mainThread())
.as(RxLife.as(this))
.subscribe(aLong -> {
Log.e("LJX", "accept=" + aLong + " Thread=" + Thread.currentThread());
});同时指定线程回调及生命周期
Observable.intervalRange(1, 100, 0, 200, TimeUnit.MILLISECONDS)
//在主线程回调，并指定在onStop关闭管道，也可以指定其它生命周期，不指定默认在onDestroy关闭管道
.as(RxLife.asOnMain(this, Event.ON_STOP))
.subscribe(aLong -> {
Log.e("LJX", "accept=" + aLong + " Thread=" + Thread.currentThread());
});
//等价于
Observable.intervalRange(1, 100, 0, 200, TimeUnit.MILLISECONDS)
.observeOn(AndroidSchedulers.mainThread())
.as(RxLife.as(this, Event.ON_STOP))
.subscribe(aLong -> {
Log.e("LJX", "accept=" + aLong + " Thread=" + Thread.currentThread());
});ok，as操作符用法就这么多，如果有更好的idea，请告诉我。
小彩蛋
RxLife类里面的as系列方法，皆适用于Observable、Flowable、ParallelFlowable、Single、Maybe、Completable这6个被观察者对象，道理都一样，这里不在一一讲解。
有疑问，请留言，我会在第一时间作答。
扩展
RxLife结合HttpSender发送请求，简直不要太爽。
HttpSender详情请点击HttpSender OkHttp+RxJava超好用、功能超级强大的Http请求框架