RxJava2 入门详细笔记（2）-原创手记-慕课网

六、过滤操作符

6.1、filter()

通过一定逻辑来过滤被观察者发送的事件，如果返回 true 则会发送事件，否则不会发送

        Observable.just(1, 2, 3, 4).filter(new Predicate<Integer>() {
            @Override
            public boolean test(Integer integer) throws Exception {
                return integer % 2 == 0;
            }
        }).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept : " + integer);
            }
        });

10-06 07:57:48.196 12753-12753/? E/MainActivity: accept : 2
10-06 07:57:48.196 12753-12753/? E/MainActivity: accept : 4

6.2、ofType()

过滤不符合该类型的事件

        Observable.just(1, 2, "Hi", 3, 4, "Hello").ofType(Integer.class).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept : " + integer);
            }
        });

10-06 07:59:41.265 12857-12857/leavesc.hello.rxjavademo E/MainActivity: accept : 1
10-06 07:59:41.265 12857-12857/leavesc.hello.rxjavademo E/MainActivity: accept : 2
10-06 07:59:41.265 12857-12857/leavesc.hello.rxjavademo E/MainActivity: accept : 3
10-06 07:59:41.265 12857-12857/leavesc.hello.rxjavademo E/MainActivity: accept : 4

6.3、skip()

以正序跳过指定数量的事件

        Observable.just(1, 2, 3, 4).skip(2).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept : " + integer);
            }
        });

10-06 08:01:09.183 12971-12971/leavesc.hello.rxjavademo E/MainActivity: accept : 3
10-06 08:01:09.183 12971-12971/leavesc.hello.rxjavademo E/MainActivity: accept : 4

6.4、skipLast()

以反序跳过指定数量的事件

        Observable.just(1, 2, 3, 4).skipLast(2).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept : " + integer);
            }
        });

10-06 08:02:00.753 13079-13079/leavesc.hello.rxjavademo E/MainActivity: accept : 1
10-06 08:02:00.753 13079-13079/leavesc.hello.rxjavademo E/MainActivity: accept : 2

6.5、distinct()

过滤事件序列中的重复事件

        Observable.just(1, 2, 1, 2, 3, 4, 3).distinct().subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept : " + integer);
            }
        });

10-06 08:03:27.402 13189-13189/leavesc.hello.rxjavademo E/MainActivity: accept : 1
10-06 08:03:27.402 13189-13189/leavesc.hello.rxjavademo E/MainActivity: accept : 2
10-06 08:03:27.402 13189-13189/leavesc.hello.rxjavademo E/MainActivity: accept : 3
10-06 08:03:27.402 13189-13189/leavesc.hello.rxjavademo E/MainActivity: accept : 4

6.6、distinctUntilChanged()

过滤掉连续重复的事件

        Observable.just(1, 2, 2, 1, 3, 4, 3, 3).distinctUntilChanged().subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept : " + integer);
            }
        });

10-06 08:04:44.531 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 1
10-06 08:04:44.541 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 2
10-06 08:04:44.541 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 1
10-06 08:04:44.541 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 3
10-06 08:04:44.541 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 4
10-06 08:04:44.541 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 3

6.7、take()

控制观察者接收事件的数量

        Observable.just(1, 2, 2, 1, 3, 4, 3, 3).take(3).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept : " + integer);
            }
        });

10-06 08:05:43.520 13397-13397/? E/MainActivity: accept : 1
10-06 08:05:43.520 13397-13397/? E/MainActivity: accept : 2
10-06 08:05:43.520 13397-13397/? E/MainActivity: accept : 2

6.8、debounce()

如果两个事件发送的时间间隔小于设定的时间间隔，则前一件事件不会发送给观察者

 Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(ObservableEmitter<Integer> emitter) throws Exception {
                emitter.onNext(1);
                Thread.sleep(900);
                emitter.onNext(2);
            }
        }).debounce(1, TimeUnit.SECONDS).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept : " + integer);
            }
        });

10-06 08:08:59.337 13509-13523/leavesc.hello.rxjavademo E/MainActivity: accept : 2

6.9、firstElement() && lastElement()

firstElement() 取事件序列的第一个元素，lastElement() 取事件序列的最后一个元素

        Observable.just(1, 2, 3, 4, 5).firstElement().subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept : " + integer);
            }
        });

6.10、elementAt() & elementAtOrError()

elementAt() 可以指定取出事件序列中事件，但是输入的 index 超出事件序列的总数的话就不会触发任何调用，想触发异常信息的话就用 elementAtOrError()

        Observable.just(1, 2, 3, 4, 5).elementAt(5).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept : " + integer);
            }
        });

以上代码不会触发任何

改用为 elementAtOrError()，则会抛出异常

        Observable.just(1, 2, 3, 4, 5).elementAtOrError(5).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept : " + integer);
            }
        });

Process: leavesc.hello.rxjavademo, PID: 13948
    io.reactivex.exceptions.OnErrorNotImplementedException: The exception was not handled due to missing onError handler in the subscribe() method call. Further reading: https://github.com/ReactiveX/RxJava/wiki/Error-Handling | null
        at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:704)
        at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:701)
        at io.reactivex.internal.observers.ConsumerSingleObserver.onError(ConsumerSingleObserver.java:46)
        at io.reactivex.internal.operators.observable.ObservableElementAtSingle$ElementAtObserver.onComplete(ObservableElementAtSingle.java:115)
        at io.reactivex.internal.operators.observable.ObservableFromArray$FromArrayDisposable.run(ObservableFromArray.java:111)
        at io.reactivex.internal.operators.observable.ObservableFromArray.subscribeActual(ObservableFromArray.java:37)
        at io.reactivex.Observable.subscribe(Observable.java:12090)
        at io.reactivex.internal.operators.observable.ObservableElementAtSingle.subscribeActual(ObservableElementAtSingle.java:37)
        at io.reactivex.Single.subscribe(Single.java:3438)
        at io.reactivex.Single.subscribe(Single.java:3424)

七、条件操作符

7.1、all()

判断事件序列是否全部满足某个事件，如果都满足则返回 true，反之则返回 false

        Observable.just(1, 2, 3, 4, 5).all(new Predicate<Integer>() {
            @Override
            public boolean test(Integer integer) throws Exception {
                return integer % 2 == 0;
            }
        }).subscribe(new Consumer<Boolean>() {
            @Override
            public void accept(Boolean aBoolean) throws Exception {
                Log.e(TAG, "accept: " + aBoolean);
            }
        });

10-06 08:16:10.212 14043-14043/leavesc.hello.rxjavademo E/MainActivity: accept: false

7.2、takeWhile()

发射原始 Observable，直到指定的某个条件不成立的那一刻，它停止发射原始 Observable，并终止自己的 Observable

Observable.just(1, 2, 3, 4, 5, 1, 2).takeWhile(new Predicate<Integer>() {
            @Override
            public boolean test(Integer integer) throws Exception {
                return integer < 4;
            }
        }).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept: " + integer);
            }
        });

10-06 14:03:42.110 20095-20095/leavesc.hello.rxjavademo E/MainActivity: accept: 1
10-06 14:03:42.110 20095-20095/leavesc.hello.rxjavademo E/MainActivity: accept: 2
10-06 14:03:42.110 20095-20095/leavesc.hello.rxjavademo E/MainActivity: accept: 3

7.3、skipWhile()

订阅原始的 Observable，但是忽略它的发射物，直到指定的某个条件变为 false 时才开始发射原始 Observable

            Observable.just(1, 2, 4, 1, 3, 4, 5, 1, 5)
                .skipWhile(new Predicate<Integer>() {
                    @Override
                    public boolean test(Integer integer) throws Exception {
                        return integer < 3;
                    }
                })
                .subscribe(new Consumer<Integer>() {
                    @Override
                    public void accept(Integer integer) throws Exception {
                        Log.e(TAG, "integer " + integer);
                    }
                });

10-06 13:59:40.583 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 4
10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 1
10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 3
10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 4
10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 5
10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 1
10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 5

7.4、takeUntil()

用于设置一个条件，当事件满足此条件时，此事件会被发送，但之后的事件就不会被发送了

Observable.just(1, 2, 4, 1, 3, 4, 5, 1, 5)
                .takeUntil(new Predicate<Integer>() {
                    @Override
                    public boolean test(Integer integer) throws Exception {
                        return integer > 3;
                    }
                })
                .subscribe(new Consumer<Integer>() {
                    @Override
                    public void accept(Integer integer) throws Exception {
                        Log.e(TAG, "integer " + integer);
                    }
                });

10-06 08:54:24.833 17208-17208/? E/MainActivity: integer 1
10-06 08:54:24.833 17208-17208/? E/MainActivity: integer 2
10-06 08:54:24.833 17208-17208/? E/MainActivity: integer 4

7.5、skipUntil()

当 skipUntil() 中的 Observable 发送事件了，原始的 Observable 才会发送事件给观察者

Observable.intervalRange(1, 6, 0, 1, TimeUnit.SECONDS)
                .skipUntil(Observable.intervalRange(10, 3, 1, 1, TimeUnit.SECONDS))
                .subscribe(new Observer<Long>() {
                    @Override
                    public void onSubscribe(Disposable d) {
                        Log.e(TAG, "onSubscribe");
                    }

                    @Override
                    public void onNext(Long along) {
                        Log.e(TAG, "onNext : " + along);
                    }

                    @Override
                    public void onError(Throwable e) {
                        Log.e(TAG, "onError");
                    }

                    @Override
                    public void onComplete() {
                        Log.e(TAG, "onComplete");
                    }
                });

10-06 08:51:16.926 16877-16877/leavesc.hello.rxjavademo E/MainActivity: onSubscribe
10-06 08:51:17.946 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onNext : 2
10-06 08:51:18.936 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onNext : 3
10-06 08:51:19.946 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onNext : 4
10-06 08:51:20.936 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onNext : 5
10-06 08:51:21.946 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onNext : 6
10-06 08:51:21.946 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onComplete

7.6、sequenceEqual()

判断两个 Observable 发送的事件是否相同，如果两个序列是相同的（相同的数据，相同的顺序，相同的终止状态），它就发射 true，否则发射 false

        Observable.sequenceEqual(Observable.just(1, 2, 3), Observable.just(1, 2, 3))
                .subscribe(new Consumer<Boolean>() {
                    @Override
                    public void accept(Boolean aBoolean) throws Exception {
                        Log.e(TAG, "accept aBoolean : " + aBoolean);
                    }
                });

10-06 08:46:59.369 16492-16492/leavesc.hello.rxjavademo E/MainActivity: accept aBoolean : true

7.7、contains()

判断事件序列中是否含有某个元素，如果有则返回 true，如果没有则返回 false

        Observable.just(1, 2, 3, 4).contains(2).subscribe(new Consumer<Boolean>() {
            @Override
            public void accept(Boolean aBoolean) throws Exception {
                Log.e(TAG, "accept aBoolean : " + aBoolean);
            }
        });

10-06 08:45:58.100 16386-16386/leavesc.hello.rxjavademo E/MainActivity: accept aBoolean : true

7.8、isEmpty()

判断事件序列是否为空

        Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(ObservableEmitter<Integer> emitter) throws Exception {
                emitter.onComplete();
            }
        }).isEmpty().subscribe(new Consumer<Boolean>() {
            @Override
            public void accept(Boolean aBoolean) throws Exception {
                Log.e(TAG, "accept aBoolean: " + aBoolean);
            }
        });

10-06 08:43:43.201 16278-16278/leavesc.hello.rxjavademo E/MainActivity: accept aBoolean: true

7.9、amb()

amb() 接收一个 Observable 集合，但是只会发送最先发送事件的 Observable 中的事件，不管发射的是一项数据还是一个 onError 或 onCompleted 通知，其余 Observable 将会被丢弃

        List<Observable<Long>> list = new ArrayList<>();
        list.add(Observable.intervalRange(1, 3, 2, 1, TimeUnit.SECONDS));
        list.add(Observable.intervalRange(10, 3, 0, 1, TimeUnit.SECONDS));
        Observable.amb(list).subscribe(new Consumer<Long>() {
            @Override
            public void accept(Long aLong) throws Exception {
                Log.e(TAG, "accept: " + aLong);
            }
        });

10-06 08:41:45.783 16053-16068/leavesc.hello.rxjavademo E/MainActivity: accept: 10
10-06 08:41:46.783 16053-16068/leavesc.hello.rxjavademo E/MainActivity: accept: 11
10-06 08:41:47.783 16053-16068/leavesc.hello.rxjavademo E/MainActivity: accept: 12

7.10、defaultIfEmpty()

如果 Observable 没有发射任何值，则可以利用这个方法发送一个默认值

        Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(ObservableEmitter<Integer> emitter) throws Exception {
                emitter.onComplete();
            }
        }).defaultIfEmpty(100).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.e(TAG, "accept: " + integer);
            }
        });

10-06 08:40:04.754 15945-15945/leavesc.hello.rxjavademo E/MainActivity: accept: 100