RxJava Operator (7) Conditional and Boolean_PHP Tutorial

RxJava Operators (7) Conditional and Boolean

In this article we will take a look at conditional and Boolean operators.

1. All/Amb
The All operator judges all the data emitted by the source Observable according to a function, and the final result returned is the judgment result. This function uses the emitted data as a parameter and internally determines whether all the data meets the judgment conditions we defined. If all are met, it returns true, otherwise it returns false.

The Amb operator can combine up to 9 Observables and let them compete. Which Observable emits data first (including onError and onComplete) will continue to emit the data of this Observable, and the data emitted by other Observables will not be discarded.

These two operators are used below. We have made such restrictions for the all operator. When the tag is false when used for the first time, an Observable of 6 numbers will be created. In the future, 5 numbers will be created. Observable.

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>private Observable<Boolean> allObserver() {<br /></li><li>Observable<Integer> just;<br /></li><li>if (tag) {<br /></li><li>just = Observable.just(1, 2, 3, 4, 5);<br /></li><li>} else {<br /></li><li>just = Observable.just(1, 2, 3, 4, 5, 6);<br /></li><li>}<br /></li><li>tag = true;<br /></li><li>return just.all(integer -> integer < 6);<br /></li><li>}<br /></li><li><br /></li><li>private Observable<Integer> ambObserver() {<br /></li><li>Observable<Integer> delay3 = Observable.just(1, 2, 3).delay(3000, TimeUnit.MILLISECONDS);<br /></li><li>Observable<Integer> delay2 = Observable.just(4, 5, 6).delay(2000, TimeUnit.MILLISECONDS);<br /></li><li>Observable<Integer> delay1 = Observable.just(7, 8, 9).delay(1000, TimeUnit.MILLISECONDS);<br /></li><li>return Observable.amb(delay1, delay2, delay3);<br /></li><li>}</li></ol>

Subscriptions

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>mLButton.setText("all");<br /></li><li>mLButton.setOnClickListener(e -> allObserver().subscribe(i -> log("all:" + i)));<br /></li><li>mRButton.setText("amb");<br /></li><li>mRButton.setOnClickListener(e -> ambObserver().subscribe(i -> log("amb:" + i)));</li></ol>

are as follows. The Observable of the 6 data returned for the first time does not meet the condition that all of them are less than 6, so the result is false. The subsequent ones all meet the condition, so the result is true. Using the amb operator's Observable, the first emitted data is 7, so 7, 8, and 9 are output, and other data are discarded.


2. Contains, IsEmpty
The Contains operator is used to determine whether the data emitted by the source Observable contains a certain data. If it does, it will return true. If the source Observable has ended If the data has not been emitted, false will be returned.
The IsEmpty operator is used to determine whether the source Observable has emitted data. If it has emitted data, it will return false. If the source Observable has ended but the data has not been emitted, it will return true.

Use these two operators to determine whether two Observable objects contain certain data and whether they are empty

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>private Observable<Boolean> containsObserver() {<br /></li><li>if (tag) {<br /></li><li>return Observable.just(1, 2, 3).contains(3);<br /></li><li>}<br /></li><li>tag = true;<br /></li><li>return Observable.just(1, 2, 3).contains(4);<br /></li><li>}<br /></li><li><br /></li><li>private Observable<Boolean> defaultObserver() {<br /></li><li>return Observable.create(new Observable.OnSubscribe<Integer>() {<br /></li><li>@Override<br /></li><li>public void call(Subscriber<? super Integer> subscriber) {<br /></li><li>subscriber.onCompleted();<br /></li><li>}<br /></li><li>}).isEmpty();<br /></li><li>}</li></ol>

respectively Subscribe

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>mLButton.setText("contains");<br /></li><li>mLButton.setOnClickListener(e -> containsObserver().subscribe(i -> log("contains:" + i)));<br /></li><li>mRButton.setText("isEmpty");<br /></li><li>mRButton.setOnClickListener(e -> defaultObserver().subscribe(i -> log("isEmpty:" + i)));</li></ol>

The operation results are as follows


3. DefaultIfEmpty
DefaultIfEmpty operator will determine whether the source Observable emits data. If If the source Observable emits data, it will emit the data normally. If not, it will emit a default data

Next we use this operator to process an empty and a non-empty Observable, if it is empty Just return to the default value 10

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>private Observable<Integer> emptyObserver() {<br /></li><li>return Observable.create(new Observable.OnSubscribe<Integer>() {<br /></li><li>@Override<br /></li><li>public void call(Subscriber<? super Integer> subscriber) {<br /></li><li>subscriber.onCompleted();<br /></li><li>}<br /></li><li>}).defaultIfEmpty(10);<br /></li><li>}<br /></li><li><br /></li><li>private Observable<Integer> notEmptyObserver() {<br /></li><li>return Observable.create(new Observable.OnSubscribe<Integer>() {<br /></li><li>@Override<br /></li><li>public void call(Subscriber<? super Integer> subscriber) {<br /></li><li>subscriber.onNext(1);<br /></li><li>subscriber.onCompleted();<br /></li><li>}<br /></li><li>}).defaultIfEmpty(10);<br /></li><li>}</li></ol>

Subscribe separately

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>mLButton.setText("empty");<br /></li><li>mLButton.setOnClickListener(e -> emptyObserver().subscribe(i -> log("empty:" + i)));<br /></li><li>mRButton.setText("notEmpty");<br /></li><li>mRButton.setOnClickListener(e -> notEmptyObserver().subscribe(i -> log("notEmpty:" + i)));</li></ol>

The running results are as follows


4. SequenceEqual
The SequenceEqual operator is used to determine whether the data sequences emitted by two Observables are the same (the emitted data is the same, the data sequence is the same, and the ending status is the same). If they are the same, it returns true, otherwise it returns false

Next, use SequenceEqual to judge two identical and different Observables

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>private Observable<Boolean> equalObserver() {<br /></li><li>return Observable.sequenceEqual(Observable.just(1, 2, 3), Observable.just(1, 2, 3));<br /></li><li>}<br /></li><li><br /></li><li>private Observable<Boolean> notEqualObserver() {<br /></li><li>return Observable.sequenceEqual(Observable.just(1, 2, 3), Observable.just(1, 2));<br /></li><li>}</li></ol>

and subscribe separately

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>mLButton.setText("equal");<br /></li><li>mLButton.setOnClickListener(e -> equalObserver().subscribe(i -> log("equal:" + i)));<br /></li><li>mRButton.setText("notequal");<br /></li><li>mRButton.setOnClickListener(e -> notEqualObserver().subscribe(i -> log("notequal:" + i)));</li></ol>

The running results are as follows


5. SkipUntil and SkipWhile
Both operators skip some data based on conditions. The difference is that SkipUnitl is It is judged based on a flag Observable. When the flag Observable does not emit data, all data emitted by the source Observable will be skipped; when the flag Observable emits a data, it starts to emit data normally. SkipWhile determines whether to skip data based on a function. When the function returns true, the data emitted by the source Observable is skipped; when the function returns false, data is emitted normally.

These two operators are used below to skip some data items.

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>private Observable<Long> skipUntilObserver() {<br /></li><li>return Observable.interval(1, TimeUnit.SECONDS).skipUntil(Observable.timer(3, TimeUnit.SECONDS));<br /></li><li>}<br /></li><li><br /></li><li>private Observable<Long> skipWhileObserver() {<br /></li><li>return Observable.interval(1, TimeUnit.SECONDS).skipWhile(aLong -> aLong < 5);<br /></li><li>}</li></ol>

Subscribe separately

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>mLButton.setText("skipUntil");<br /></li><li>mLButton.setOnClickListener(e -> skipUntilObserver().subscribe(i -> log("skipUntil:" + i)));<br /></li><li>mRButton.setText("skipWhile");<br /></li><li>mRButton.setOnClickListener(e -> skipWhileObserver().subscribe(i -> log("skipWhile:" + i)));</li></ol>

运行结果如下


六、TakeUntil、TakeWhile
TakeUntil和TakeWhile操作符可以说和SkipUnitl和SkipWhile操作符是完全相反的功能。TakeUntil也是使用一个标志Observable是否发射数据来判断，当标志Observable没有发射数据时，正常发射数据，而一旦标志Observable发射过了数据则后面的数据都会被丢弃。TakeWhile则是根据一个函数来判断是否发射数据，当函数返回值为true的时候正常发射数据；当函数返回false的时候丢弃所有后面的数据。


下面使用这两个操作符来take两个Observable发射的数据

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>private Observable<Long> takeUntilObserver() {<br /></li><li>return Observable.interval(1, TimeUnit.SECONDS).takeUntil(Observable.timer(3, TimeUnit.SECONDS));<br /></li><li>}<br /></li><li><br /></li><li>private Observable<Long> takeWhileObserver() {<br /></li><li>return Observable.interval(1, TimeUnit.SECONDS).takeWhile(aLong -> aLong < 5);<br /></li><li>}</li></ol>

分别进行订阅

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>mLButton.setText("takeUntil");<br /></li><li>mLButton.setOnClickListener(e -> takeUntilObserver().subscribe(i -> log("takeUntil:" + i)));<br /></li><li>mRButton.setText("takeWhile");<br /></li><li>mRButton.setOnClickListener(e -> takeWhileObserver().subscribe(i -> log("takeWhile:" + i)));</li></ol>

运行结果如下


关于条件和布尔操作符就到这了，本文中所有的demo程序见：https://github.com/Chaoba/RxJavaDemo

http://www.bkjia.com/PHPjc/1077808.htmlwww.bkjia.comtruehttp://www.bkjia.com/PHPjc/1077808.htmlTechArticleRxJava操作符（七）Conditional and Boolean 在这篇文章里我们来了解一下条件和布尔操作符。 一、All/Amb All操作符根据一个函数对源Observable发射的...