[英]What is the proper way to handle subscriptions in RxJava/RxAndroid for an Activity Lifecycle?
我剛剛開始使用RxJava / RxAndroid。 我想避免上下文泄漏,所以我創建了一個像這樣的BaseFragment:
public abstract class BaseFragment extends Fragment {
protected CompositeSubscription compositeSubscription = new CompositeSubscription();
@Override
public void onDestroy() {
super.onDestroy();
compositeSubscription.unsubscribe();
}
}
在我的片段中擴展了BaseFragment,我這樣做:
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;
}
所以我想我的問題是雙重的:
這會阻止上下文泄漏因為我取消訂閱onDestroy()嗎?
我是否通過在完成后將訂閱設置為null並檢查無效來正確跟蹤observable是否正在“運行”?
是的,它會停止,但你也應該在onError
中將訂閱設置為null
(或者在錯誤之后,你不會再次加載項目)。
另外不要忘記,片段可以被停止,但不會被銷毀(例如在后面的堆棧中),在這種情況下你可能不想觀察任何東西。 如果您unsubscribe
onDestroy
到onStop
請不要忘記在每次創建視圖時在onCreateView
初始化compositeSubscription
(因為在取消訂閱CompositeSubscription之后,您不再可以在那里添加訂閱)。
是,對的。 但我認為compositeSubscription.remove
可以省略,因為你已經檢查了null。
您不需要任何第三方lib來管理Activity生命周期。 請嘗試以下代碼:
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);
}
});
}
}
生命周期事件:
public enum LifecycleEvent {
ON_PAUSED,
ON_STOPPED,
ON_SAVE_INSTANCE_STATE,
ON_DESTROYED,
ON_VIEW_DESTORYED,
ON_DETACHED,
}
用法:
myObservable
.compose(LifecycleBinder.subscribeUtilEvent(this, LifecycleEvent.ON_DESTROYED))
.subscribe();
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