io.reactivex.Observable.firstElement()方法的使用及代码示例

x33g5p2x  于2022-01-25 转载在 其他  
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本文整理了Java中io.reactivex.Observable.firstElement()方法的一些代码示例，展示了Observable.firstElement()的具体用法。这些代码示例主要来源于Github/Stackoverflow/Maven等平台，是从一些精选项目中提取出来的代码，具有较强的参考意义，能在一定程度帮忙到你。Observable.firstElement()方法的具体详情如下：
包路径：io.reactivex.Observable
类名称：Observable
方法名：firstElement

Observable.firstElement介绍

[英]Returns a Maybe that emits only the very first item emitted by the source ObservableSource, or completes if the source ObservableSource is empty.

Scheduler: firstElement does not operate by default on a particular Scheduler.
[中]返回一个Maybe，该Maybe只发出源ObservableSource发出的第一个项，如果源ObservableSource为空，则返回complete。
Scheduler:firstElement默认情况下不会在特定的计划程序上运行。

代码示例

代码示例来源：origin: trello/RxLifecycle

  1. @Override
  2. public MaybeSource<T> apply(Maybe<T> upstream) {
  3.   return upstream.takeUntil(observable.firstElement());
  4. }

代码示例来源：origin: alibaba/Tangram-Android

  1. @Override
  2. public MaybeSource<T> apply(Maybe<T> upstream) {
  3.   return upstream.takeUntil(mObservable.firstElement());
  4. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateOfNoneMatchingThePredicate() {
  3.   Observable<Integer> o = Observable.just(1, 3, 5, 7, 9, 7, 5, 3, 1);
  4.   o.filter(IS_EVEN).firstElement().subscribe(wm);
  5.   verify(wm, never()).onSuccess(anyInt());
  6.   verify(wm).onComplete();
  7.   verify(wm, never()).onError(any(Throwable.class));
  8. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirst() {
  3.   Maybe<Integer> o = Observable.just(1, 2, 3).firstElement();
  4.   o.subscribe(wm);
  5.   InOrder inOrder = inOrder(wm);
  6.   inOrder.verify(wm, times(1)).onSuccess(1);
  7.   inOrder.verifyNoMoreInteractions();
  8. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstOfNone() {
  3.   Observable<Integer> o = Observable.empty();
  4.   o.firstElement().subscribe(wm);
  5.   verify(wm, never()).onSuccess(anyInt());
  6.   verify(wm).onComplete();
  7.   verify(wm, never()).onError(any(Throwable.class));
  8. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithOneElement() {
  3.   Maybe<Integer> o = Observable.just(1).firstElement();
  4.   o.subscribe(wm);
  5.   InOrder inOrder = inOrder(wm);
  6.   inOrder.verify(wm, times(1)).onSuccess(1);
  7.   inOrder.verifyNoMoreInteractions();
  8. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithOneElementObservable() {
  3.   Observable<Integer> o = Observable.just(1).firstElement().toObservable();
  4.   Observer<Integer> observer = TestHelper.mockObserver();
  5.   o.subscribe(observer);
  6.   InOrder inOrder = inOrder(observer);
  7.   inOrder.verify(observer, times(1)).onNext(1);
  8.   inOrder.verify(observer, times(1)).onComplete();
  9.   inOrder.verifyNoMoreInteractions();
  10. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstObservable() {
  3.   Observable<Integer> o = Observable.just(1, 2, 3).firstElement().toObservable();
  4.   Observer<Integer> observer = TestHelper.mockObserver();
  5.   o.subscribe(observer);
  6.   InOrder inOrder = inOrder(observer);
  7.   inOrder.verify(observer, times(1)).onNext(1);
  8.   inOrder.verify(observer, times(1)).onComplete();
  9.   inOrder.verifyNoMoreInteractions();
  10. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithEmpty() {
  3.   Maybe<Integer> o = Observable.<Integer> empty().firstElement();
  4.   o.subscribe(wm);
  5.   InOrder inOrder = inOrder(wm);
  6.   inOrder.verify(wm, times(1)).onComplete();
  7.   inOrder.verify(wm, never()).onError(any(Throwable.class));
  8.   inOrder.verifyNoMoreInteractions();
  9. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithEmptyObservable() {
  3.   Observable<Integer> o = Observable.<Integer> empty().firstElement().toObservable();
  4.   Observer<Integer> observer = TestHelper.mockObserver();
  5.   o.subscribe(observer);
  6.   InOrder inOrder = inOrder(observer);
  7.   inOrder.verify(observer).onComplete();
  8.   inOrder.verify(observer, never()).onError(any(Throwable.class));
  9.   inOrder.verifyNoMoreInteractions();
  10. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateAndEmpty() {
  3.   Maybe<Integer> o = Observable.just(1)
  4.       .filter(new Predicate<Integer>() {
  5.         @Override
  6.         public boolean test(Integer t1) {
  7.           return t1 % 2 == 0;
  8.         }
  9.       })
  10.       .firstElement();
  11.   o.subscribe(wm);
  12.   InOrder inOrder = inOrder(wm);
  13.   inOrder.verify(wm, times(1)).onComplete();
  14.   inOrder.verify(wm, never()).onError(any(Throwable.class));
  15.   inOrder.verifyNoMoreInteractions();
  16. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateAndOneElement() {
  3.   Maybe<Integer> o = Observable.just(1, 2)
  4.       .filter(new Predicate<Integer>() {
  5.         @Override
  6.         public boolean test(Integer t1) {
  7.           return t1 % 2 == 0;
  8.         }
  9.       })
  10.       .firstElement();
  11.   o.subscribe(wm);
  12.   InOrder inOrder = inOrder(wm);
  13.   inOrder.verify(wm, times(1)).onSuccess(2);
  14.   inOrder.verifyNoMoreInteractions();
  15. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicate() {
  3.   Maybe<Integer> o = Observable.just(1, 2, 3, 4, 5, 6)
  4.       .filter(new Predicate<Integer>() {
  5.         @Override
  6.         public boolean test(Integer t1) {
  7.           return t1 % 2 == 0;
  8.         }
  9.       })
  10.       .firstElement();
  11.   o.subscribe(wm);
  12.   InOrder inOrder = inOrder(wm);
  13.   inOrder.verify(wm, times(1)).onSuccess(2);
  14.   inOrder.verifyNoMoreInteractions();
  15. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateAndEmptyObservable() {
  3.   Observable<Integer> o = Observable.just(1)
  4.       .filter(new Predicate<Integer>() {
  5.         @Override
  6.         public boolean test(Integer t1) {
  7.           return t1 % 2 == 0;
  8.         }
  9.       })
  10.       .firstElement().toObservable();
  11.   Observer<Integer> observer = TestHelper.mockObserver();
  12.   o.subscribe(observer);
  13.   InOrder inOrder = inOrder(observer);
  14.   inOrder.verify(observer).onComplete();
  15.   inOrder.verify(observer, never()).onError(any(Throwable.class));
  16.   inOrder.verifyNoMoreInteractions();
  17. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateObservable() {
  3.   Observable<Integer> o = Observable.just(1, 2, 3, 4, 5, 6)
  4.       .filter(new Predicate<Integer>() {
  5.         @Override
  6.         public boolean test(Integer t1) {
  7.           return t1 % 2 == 0;
  8.         }
  9.       })
  10.       .firstElement().toObservable();
  11.   Observer<Integer> observer = TestHelper.mockObserver();
  12.   o.subscribe(observer);
  13.   InOrder inOrder = inOrder(observer);
  14.   inOrder.verify(observer, times(1)).onNext(2);
  15.   inOrder.verify(observer, times(1)).onComplete();
  16.   inOrder.verifyNoMoreInteractions();
  17. }

代码示例来源：origin: ReactiveX/RxJava

  1. @Test
  2. public void testFirstWithPredicateAndOneElementObservable() {
  3.   Observable<Integer> o = Observable.just(1, 2)
  4.       .filter(new Predicate<Integer>() {
  5.         @Override
  6.         public boolean test(Integer t1) {
  7.           return t1 % 2 == 0;
  8.         }
  9.       })
  10.       .firstElement().toObservable();
  11.   Observer<Integer> observer = TestHelper.mockObserver();
  12.   o.subscribe(observer);
  13.   InOrder inOrder = inOrder(observer);
  14.   inOrder.verify(observer, times(1)).onNext(2);
  15.   inOrder.verify(observer, times(1)).onComplete();
  16.   inOrder.verifyNoMoreInteractions();
  17. }

代码示例来源：origin: ReactiveX/RxJava

  1. @SuppressWarnings("unchecked")
  2. @Test
  3. public void noSubsequentSubscriptionIterable() {
  4.   final int[] calls = { 0 };
  5.   Observable<Integer> source = Observable.create(new ObservableOnSubscribe<Integer>() {
  6.     @Override
  7.     public void subscribe(ObservableEmitter<Integer> s) throws Exception {
  8.       calls[0]++;
  9.       s.onNext(1);
  10.       s.onComplete();
  11.     }
  12.   });
  13.   Observable.concat(Arrays.asList(source, source)).firstElement()
  14.   .test()
  15.   .assertResult(1);
  16.   assertEquals(1, calls[0]);
  17. }

代码示例来源：origin: ReactiveX/RxJava

  1. @SuppressWarnings("unchecked")
  2. @Test
  3. public void noSubsequentSubscriptionDelayErrorIterable() {
  4.   final int[] calls = { 0 };
  5.   Observable<Integer> source = Observable.create(new ObservableOnSubscribe<Integer>() {
  6.     @Override
  7.     public void subscribe(ObservableEmitter<Integer> s) throws Exception {
  8.       calls[0]++;
  9.       s.onNext(1);
  10.       s.onComplete();
  11.     }
  12.   });
  13.   Observable.concatDelayError(Arrays.asList(source, source)).firstElement()
  14.   .test()
  15.   .assertResult(1);
  16.   assertEquals(1, calls[0]);
  17. }

代码示例来源：origin: ReactiveX/RxJava

  1. @SuppressWarnings("unchecked")
  2. @Test
  3. public void noSubsequentSubscription() {
  4.   final int[] calls = { 0 };
  5.   Observable<Integer> source = Observable.create(new ObservableOnSubscribe<Integer>() {
  6.     @Override
  7.     public void subscribe(ObservableEmitter<Integer> s) throws Exception {
  8.       calls[0]++;
  9.       s.onNext(1);
  10.       s.onComplete();
  11.     }
  12.   });
  13.   Observable.concatArray(source, source).firstElement()
  14.   .test()
  15.   .assertResult(1);
  16.   assertEquals(1, calls[0]);
  17. }

代码示例来源：origin: ReactiveX/RxJava

  1. @SuppressWarnings("unchecked")
  2. @Test
  3. public void noSubsequentSubscriptionDelayError() {
  4.   final int[] calls = { 0 };
  5.   Observable<Integer> source = Observable.create(new ObservableOnSubscribe<Integer>() {
  6.     @Override
  7.     public void subscribe(ObservableEmitter<Integer> s) throws Exception {
  8.       calls[0]++;
  9.       s.onNext(1);
  10.       s.onComplete();
  11.     }
  12.   });
  13.   Observable.concatArrayDelayError(source, source).firstElement()
  14.   .test()
  15.   .assertResult(1);
  16.   assertEquals(1, calls[0]);
  17. }

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