[英]What is the proper way to handle subscriptions in RxJava/RxAndroid for an Activity Lifecycle?
I am just getting started on RxJava/RxAndroid. 我刚刚开始使用RxJava / RxAndroid。 I want to avoid context leaks so I created a BaseFragment like so: 我想避免上下文泄漏,所以我创建了一个像这样的BaseFragment:
public abstract class BaseFragment extends Fragment {
protected CompositeSubscription compositeSubscription = new CompositeSubscription();
@Override
public void onDestroy() {
super.onDestroy();
compositeSubscription.unsubscribe();
}
}
And inside my fragment that extends BaseFragment, I am doing this: 在我的片段中扩展了BaseFragment,我这样做:
protected void fetchNewerObjects(){
if(!areNewerObjectsFetching()){ //if it is not already fetching newer objects
Runtime.getRuntime().gc();//clean out memory if possible
fetchNewObjectsSubscription = Observable
.just(new Object1())
.map(new Func1<Object1, Object2>() {
@Override
public Object2 call(Object1 obj1) {
//do bg stuff
return obj2;
}
})
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Observer<Object2>() {
@Override
public void onCompleted() {
compositeSubscription.remove(fetchNewObjectsSubscription);
fetchNewObjectsSubscription = null;
}
@Override
public void onError(Throwable e) {
}
@Override
public void onNext(ArrayList<NewsFeedObject> newsFeedObjects) {
//do stuff
}
});
//add subscription to composite subscription so it can be unsubscribed onDestroy()
compositeSubscription.add(fetchNewObjectsSubscription);
}
}
protected boolean areNewerObjectsFetching(){
if(fetchNewObjectsSubscription == null || fetchNewObjectsSubscription.isUnsubscribed()){ //if its either null or is in a finished status
return false;
}
return true;
}
So I guess my question is two-fold: 所以我想我的问题是双重的:
Will this stop context leaks because I am unsubscribing onDestroy()? 这会阻止上下文泄漏因为我取消订阅onDestroy()吗?
And am I properly keeping track of wether the observable is "running" by setting the subscription to null after completion and checking the nullity? 我是否通过在完成后将订阅设置为null并检查无效来正确跟踪observable是否正在“运行”?
Yes, it will stop, but you should also set subscription to null
in onError
too (or after error, you won't load items again). 是的,它会停止,但你也应该在onError
中将订阅设置为null
(或者在错误之后,你不会再次加载项目)。
Also do not forget that fragment can be stopped, but not destroyed (in back stack, for example) and you might not want to observe anything in this case. 另外不要忘记,片段可以被停止,但不会被销毁(例如在后面的堆栈中),在这种情况下你可能不想观察任何东西。 If you move unsubscribe
from onDestroy
to onStop
do not forget to initialise compositeSubscription
in onCreateView
each time view is created (because after CompositeSubscription is unsubscribed you no longer can add subscriptions there). 如果您unsubscribe
onDestroy
到onStop
请不要忘记在每次创建视图时在onCreateView
初始化compositeSubscription
(因为在取消订阅CompositeSubscription之后,您不再可以在那里添加订阅)。
Yes correct. 是,对的。 But I think that compositeSubscription.remove
can be omitted, because you already check for null. 但我认为compositeSubscription.remove
可以省略,因为你已经检查了null。
You don't need any third-party lib to manage Activity lifecycle. 您不需要任何第三方lib来管理Activity生命周期。 Try the following codes: 请尝试以下代码:
public class LifecycleBinder {
public static <R> Observable.Transformer<R, R> subscribeUtilEvent(final Activity target, LifecycleEvent event) {
final Application app = target.getApplication();
final PublishSubject<LifecycleEvent> publishSubject = PublishSubject.create();
final Application.ActivityLifecycleCallbacks callbacks = new Application.ActivityLifecycleCallbacks() {
@Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
}
@Override
public void onActivityStarted(Activity activity) {
}
@Override
public void onActivityResumed(Activity activity) {
}
@Override
public void onActivityPaused(Activity activity) {
if (activity == target)
publishSubject.onNext(LifecycleEvent.ON_PAUSED);
}
@Override
public void onActivityStopped(Activity activity) {
if (activity == target)
publishSubject.onNext(LifecycleEvent.ON_STOPPED);
}
@Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
if (activity == target)
publishSubject.onNext(LifecycleEvent.ON_SAVE_INSTANCE_STATE);
}
@Override
public void onActivityDestroyed(Activity activity) {
if (activity == target)
publishSubject.onNext(LifecycleEvent.ON_DESTROYED);
}
};
app.registerActivityLifecycleCallbacks(callbacks);
return subscribeUtilEvent(publishSubject, event, new Action0() {
@Override
public void call() {
app.unregisterActivityLifecycleCallbacks(callbacks);
}
});
}
public static <R> Observable.Transformer<R, R> subscribeUtilEvent(final Fragment target, LifecycleEvent event) {
final FragmentManager manager = target.getFragmentManager();
if (manager == null) {
throw new NullPointerException("fragment manager is null!");
}
final PublishSubject<LifecycleEvent> publishSubject = PublishSubject.create();
final FragmentManager.FragmentLifecycleCallbacks callbacks = manager.new FragmentLifecycleCallbacks() {
@Override
public void onFragmentPreAttached(FragmentManager fm, Fragment f, Context context) {
}
@Override
public void onFragmentAttached(FragmentManager fm, Fragment f, Context context) {
}
@Override
public void onFragmentCreated(FragmentManager fm, Fragment f, Bundle savedInstanceState) {
}
@Override
public void onFragmentActivityCreated(FragmentManager fm, Fragment f, Bundle savedInstanceState) {
}
@Override
public void onFragmentViewCreated(FragmentManager fm, Fragment f, View v, Bundle savedInstanceState) {
}
@Override
public void onFragmentStarted(FragmentManager fm, Fragment f) {
}
@Override
public void onFragmentResumed(FragmentManager fm, Fragment f) {
}
@Override
public void onFragmentPaused(FragmentManager fm, Fragment f) {
if (f == target)
publishSubject.onNext(LifecycleEvent.ON_PAUSED);
}
@Override
public void onFragmentStopped(FragmentManager fm, Fragment f) {
if (f == target)
publishSubject.onNext(LifecycleEvent.ON_STOPPED);
}
@Override
public void onFragmentSaveInstanceState(FragmentManager fm, Fragment f, Bundle outState) {
if (f == target)
publishSubject.onNext(LifecycleEvent.ON_SAVE_INSTANCE_STATE);
}
@Override
public void onFragmentViewDestroyed(FragmentManager fm, Fragment f) {
if (f == target)
publishSubject.onNext(LifecycleEvent.ON_VIEW_DESTORYED);
}
@Override
public void onFragmentDestroyed(FragmentManager fm, Fragment f) {
if (f == target)
publishSubject.onNext(LifecycleEvent.ON_DESTROYED);
}
@Override
public void onFragmentDetached(FragmentManager fm, Fragment f) {
if (f == target)
publishSubject.onNext(LifecycleEvent.ON_DESTROYED);
}
};
manager.registerFragmentLifecycleCallbacks(callbacks, true);
return subscribeUtilEvent(publishSubject, event, new Action0() {
@Override
public void call() {
manager.unregisterFragmentLifecycleCallbacks(callbacks);
}
});
}
private static <R, T> Observable.Transformer<R, R> subscribeUtilEvent(final Observable<T> source, final T event, final Action0 doOnComplete) {
return new Observable.Transformer<R, R>() {
@Override
public Observable<R> call(Observable<R> rObservable) {
return rObservable.takeUntil(takeUntilEvent(source, event)).doOnCompleted(doOnComplete);
}
};
}
private static <T> Observable<T> takeUntilEvent(final Observable<T> src, final T event) {
return src.takeFirst(new Func1<T, Boolean>() {
@Override
public Boolean call(T lifecycleEvent) {
return lifecycleEvent.equals(event);
}
});
}
}
Lifecycle events: 生命周期事件:
public enum LifecycleEvent {
ON_PAUSED,
ON_STOPPED,
ON_SAVE_INSTANCE_STATE,
ON_DESTROYED,
ON_VIEW_DESTORYED,
ON_DETACHED,
}
Usage: 用法:
myObservable
.compose(LifecycleBinder.subscribeUtilEvent(this, LifecycleEvent.ON_DESTROYED))
.subscribe();
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