RxJava 过滤操作符 skip,skipLast,task,takeLast

时间：2021-05-26 17:44:59

skipe(n)操作符跳过源Obsrvable的前面n个数据项

  Observable.range(1, 10).skip(5).subscribe(new Action1<Integer>() {
            @Override
            public void call(Integer integer) {
                LogUtils.d("----->call():" + integer);
            }
        });

结果:

03-03 16:19:25.340 27107-27107/com.rxandroid.test1 D/----->: ----->call():6
03-03 16:19:25.340 27107-27107/com.rxandroid.test1 D/----->: ----->call():7
03-03 16:19:25.340 27107-27107/com.rxandroid.test1 D/----->: ----->call():8
03-03 16:19:25.340 27107-27107/com.rxandroid.test1 D/----->: ----->call():9
03-03 16:19:25.340 27107-27107/com.rxandroid.test1 D/----->: ----->call():10


skip(long time,TimeUnit) 是跳过多少秒 然后才开始将后面产生的数据提交给订阅者

Observable.interval(1, TimeUnit.SECONDS).sample(3, TimeUnit.SECONDS, Schedulers.newThread()).subscribe(new Observer<Long>() {
            @Override
            public void onCompleted() {
                LogUtils.d("-------->onCompleted()");
            }

            @Override
            public void onError(Throwable e) {
                LogUtils.d("-------->onError()" + e);
            }

            @Override
            public void onNext(Long aLong) {
                LogUtils.d("-------->onNext()" + aLong + "   thread:" + Thread.currentThread().getName());
            }
        });
结果:忽略了0,1

03-03 16:27:42.250 10652-11254/com.rxandroid.test1 D/----->: ----->call():1  time:16:03:42
03-03 16:27:43.250 10652-11254/com.rxandroid.test1 D/----->: ----->call():2  time:16:03:43
03-03 16:27:44.250 10652-11254/com.rxandroid.test1 D/----->: ----->call():3  time:16:03:44
03-03 16:27:45.250 10652-11254/com.rxandroid.test1 D/----->: ----->call():4  time:16:03:45
03-03 16:27:46.250 10652-11254/com.rxandroid.test1 D/----->: ----->call():5  time:16:03:46
03-03 16:27:47.250 10652-11254/com.rxandroid.test1 D/----->: ----->call():6  time:16:03:47
03-03 16:27:48.250 10652-11254/com.rxandroid.test1 D/----->: ----->call():7  time:16:03:48
03-03 16:27:49.250 10652-11254/com.rxandroid.test1 D/----->: ----->call():8  time:16:03:49
03-03 16:27:50.250 10652-11254/com.rxandroid.test1 D/----->: ----->call():9  time:16:03:50



skipLast 正好和skip 相反，忽略最后产生的n个数据项

 Observable.range(1, 10).skipLast(5).subscribe(new Action1<Integer>() {
            @Override
            public void call(Integer integer) {
                LogUtils.d("----->call():" + integer + "  time:" + DateFormat.format("HH:MM:ss", System.currentTimeMillis()));
            }
        });


结果:

03-03 16:32:33.240 19805-19805/com.rxandroid.test1 D/----->: ----->call():1  time:16:03:33
03-03 16:32:33.250 19805-19805/com.rxandroid.test1 D/----->: ----->call():2  time:16:03:33
03-03 16:32:33.250 19805-19805/com.rxandroid.test1 D/----->: ----->call():3  time:16:03:33
03-03 16:32:33.250 19805-19805/com.rxandroid.test1 D/----->: ----->call():4  time:16:03:33
03-03 16:32:33.250 19805-19805/com.rxandroid.test1 D/----->: ----->call():5  time:16:03:33


skipLast(long time,TimeUnit)  忽略最后时间单位内产生的数据

例子:

 Observable.interval(1, TimeUnit.SECONDS).take(10).skipLast(5, TimeUnit.SECONDS).subscribe(new Action1<Long>() {
            @Override
            public void call(Long integer) {
                LogUtils.d("----->call():" + integer + "  time:" + DateFormat.format("HH:MM:ss", System.currentTimeMillis()));
            }
        });


结果:

03-03 16:34:50.860 23169-24170/com.rxandroid.test1 D/----->: ----->call():0  time:16:03:50
03-03 16:34:50.860 23169-24170/com.rxandroid.test1 D/----->: ----->call():1  time:16:03:50
03-03 16:34:52.860 23169-24170/com.rxandroid.test1 D/----->: ----->call():2  time:16:03:52
03-03 16:34:53.860 23169-24170/com.rxandroid.test1 D/----->: ----->call():3  time:16:03:53
03-03 16:34:53.860 23169-24170/com.rxandroid.test1 D/----->: ----->call():4  time:16:03:53

关于take的操作符，想必通过前面的文章，您应该很熟悉,这里还是回顾一下吧

take(n) 并不是娶第n个，而是取前面n个数据

例子:

   Observable.range(1,10).take(5).subscribe(new Action1<Integer>() {
            @Override
            public void call(Integer integer) {
                LogUtils.d("-------->onNext()" + integer);
            }
        });
结果:

03-03 16:41:10.790 3005-3005/com.rxandroid.test1 D/----->: -------->onNext()1
03-03 16:41:10.790 3005-3005/com.rxandroid.test1 D/----->: -------->onNext()2
03-03 16:41:10.790 3005-3005/com.rxandroid.test1 D/----->: -------->onNext()3
03-03 16:41:10.790 3005-3005/com.rxandroid.test1 D/----->: -------->onNext()4
03-03 16:41:10.800 3005-3005/com.rxandroid.test1 D/----->: -------->onNext()5


关于 take(longtime, TimeUnit unit)  是在制定时间内取数据，如果超过了这个时间源Observable产生的数据将作废,例子就不演示了


takeFirst操作符和first操作符类似,取满足条件的第一个

区别:

1:first 娶不到要抛异常,takeFirst不会

 Observable.range(1, 10).takeFirst(new Func1<Integer, Boolean>() {
            @Override
            public Boolean call(Integer integer) {
                return integer > 10;
            }
        }).subscribe(new Observer<Integer>() {
            @Override
            public void onCompleted() {
                LogUtils.d("------>takeFirst onCompleted");
            }

            @Override
            public void onError(Throwable e) {
                LogUtils.d("------>takeFirst onError:" + e);
            }

            @Override
            public void onNext(Integer integer) {
                LogUtils.d("------>takeFirst onNext:" + integer);
            }
        });

        Observable.range(10, 10).first(new Func1<Integer, Boolean>() {
            @Override
            public Boolean call(Integer integer) {
                return integer > 20;
            }
        }).subscribe(new Observer<Integer>() {
            @Override
            public void onCompleted() {
                LogUtils.d("------>first onCompleted");
            }

            @Override
            public void onError(Throwable e) {
                LogUtils.d("------>first onError:" + e);
            }

            @Override
            public void onNext(Integer integer) {
                LogUtils.d("------>first onNext:" + integer);
            }
        });

结果:

03-03 16:50:52.410 21900-21900/com.rxandroid.test1 D/----->: ------>takeFirst onCompleted
03-03 16:50:52.410 21900-21900/com.rxandroid.test1 D/----->: ------>first onError:java.util.NoSuchElementException: Sequence contains no elements


takeLast操作符与last操作符相似,区别在于，如果娶不到满足条件的值,last将抛出异常,这里就不演示了




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