Rxjava3使用教程：操作符-过滤

2022-05-05 本文已影响0人 Alsan_L3

过滤操作符

根据应用场景对过滤操作符进行分类，可分成以下4个类别：

1. 根据"指定条件"过滤事件

操作符	作用
filter	过滤特定条件的事件
ofType	过滤特定数据类型的数据
skip/skipLast	跳过某个事件
distinct/distinctUntilChanged	过滤事件序列中重复的事件 / 连续重复的事件

filter()

Observable.just("hello", 1, "haha", 2).filter(new Predicate<Serializable>() {
    @Override
    public boolean test(Serializable serializable) throws Throwable {
        return serializable instanceof Integer;
    }
}).subscribe(observer);

结果：

2022-05-05 14:59:17.674 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onSubscribe:
2022-05-05 14:59:17.674 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:1
2022-05-05 14:59:17.675 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:2
2022-05-05 14:59:17.675 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onComplete

ofType()

Observable.just(1,2,"hello").ofType(String.class).subscribe(observer);

结果：

2022-05-05 14:58:09.137 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onSubscribe:
2022-05-05 14:58:09.137 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:hello
2022-05-05 14:58:09.137 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onComplete

skip()

Observable.just(1,2,3,4,5).skip(2).subscribe(observer);

结果：

2022-05-05 15:00:10.151 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onSubscribe:
2022-05-05 15:00:10.151 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:3
2022-05-05 15:00:10.151 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:4
2022-05-05 15:00:10.152 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:5
2022-05-05 15:00:10.152 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onComplete

skipLast()

Observable.just(1,2,3,4,5).skipLast(3).subscribe(observer);

结果：

2022-05-05 15:01:03.328 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onSubscribe:
2022-05-05 15:01:03.328 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:1
2022-05-05 15:01:03.328 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:2
2022-05-05 15:01:03.328 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onComplete

distinct()

//过滤事件序列中重复的事件
Observable.just(1,2,2,4,4,5,6, 1).distinct().subscribe(observer);

结果：

2022-05-05 15:01:42.336 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onSubscribe:
2022-05-05 15:01:42.337 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:1
2022-05-05 15:01:42.337 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:2
2022-05-05 15:01:42.337 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:4
2022-05-05 15:01:42.337 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:5
2022-05-05 15:01:42.337 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:6
2022-05-05 15:01:42.337 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onComplete

distinctUntilChanged()

//过滤事件序列中连续重复的事件
Observable.just(1,2,2,4,4,5,6, 1).distinctUntilChanged().subscribe(observer);

结果：

2022-05-05 15:02:07.275 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onSubscribe:
2022-05-05 15:02:07.276 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:1
2022-05-05 15:02:07.276 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:2
2022-05-05 15:02:07.276 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:4
2022-05-05 15:02:07.276 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:5
2022-05-05 15:02:07.276 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:6
2022-05-05 15:02:07.276 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:1
2022-05-05 15:02:07.276 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onComplete

2. 根据"指定事件数量"过滤事件

操作符	作用
take	指定观察者最多能接收到的事件数量
takeLast	指定观察者只能接收到被观察者发送的最后几个事件

take

Observable.just(1,2,3,4,5).take(2).subscribe(observer);

结果:

2022-05-05 15:06:45.219 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onSubscribe:
2022-05-05 15:06:45.219 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:1
2022-05-05 15:06:45.219 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:2
2022-05-05 15:06:45.219 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onComplete

takeLast

Observable.just(1,2,3,4,5).takeLast(1).subscribe(observer);

结果:

2022-05-05 15:06:58.362 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onSubscribe:
2022-05-05 15:06:58.363 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onNext:5
2022-05-05 15:06:58.363 1522-1522/com.alsan.rxjavademo D/RxFilterSymbolActivity: onComplete

3. 根据"指定时间"过滤事件

操作符	作用
throttleFirst	在某段时间内，只发送该段时间内第1次事件
throttleLast/sample	在某段时间内，只发送该段时间内最后1次事件
throttleWithTimeout / debounce	发送数据事件时，若2次发送事件的间隔＜指定时间，就会丢弃前一次的数据，直到指定时间内都没有新数据发射时才会发送后一次的数据

throttleFirst

Observable.create(new ObservableOnSubscribe<Integer>() {
    @Override
    public void subscribe(ObservableEmitter<Integer> e) throws Exception {
        // 隔段事件发送时间
        e.onNext(1);
        Thread.sleep(500);

        e.onNext(2);
        Thread.sleep(400);

        e.onNext(3);
        Thread.sleep(300);

        e.onNext(4);
        Thread.sleep(300);

        e.onNext(5);
        Thread.sleep(300);

        e.onNext(6);
        Thread.sleep(400);

        e.onNext(7);
        Thread.sleep(300);
        e.onNext(8);

        Thread.sleep(300);
        e.onNext(9);

        Thread.sleep(300);
        e.onComplete();
    }
}).throttleFirst(1, TimeUnit.SECONDS)//每1秒中采用数据
        .subscribe(new Observer<Integer>() {
            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, "开始采用subscribe连接");
            }

            @Override
            public void onNext(Integer value) {
                Log.d(TAG, "接收到了事件"+ value  );
            }

            @Override
            public void onError(Throwable e) {
                Log.d(TAG, "对Error事件作出响应");
            }

            @Override
            public void onComplete() {
                Log.d(TAG, "对Complete事件作出响应");
            }
        });

结果：

2022-05-05 15:27:20.009 3744-3744/com.alsan.rxjavademo D/RxFilterSymbolActivity: 开始采用subscribe连接
2022-05-05 15:27:20.009 3744-3744/com.alsan.rxjavademo D/RxFilterSymbolActivity: 接收到了事件1
2022-05-05 15:27:21.214 3744-3744/com.alsan.rxjavademo D/RxFilterSymbolActivity: 接收到了事件4
2022-05-05 15:27:22.218 3744-3744/com.alsan.rxjavademo D/RxFilterSymbolActivity: 接收到了事件7
2022-05-05 15:27:23.121 3744-3744/com.alsan.rxjavademo D/RxFilterSymbolActivity: 对Complete事件作出响应

throttleLast/sample

Observable.create(new ObservableOnSubscribe<Integer>() {
    @Override
    public void subscribe(ObservableEmitter<Integer> e) throws Exception {
        // 隔段事件发送时间
        e.onNext(1);
        Thread.sleep(500);

        e.onNext(2);
        Thread.sleep(400);

        e.onNext(3);
        Thread.sleep(300);

        e.onNext(4);
        Thread.sleep(300);

        e.onNext(5);
        Thread.sleep(300);

        e.onNext(6);
        Thread.sleep(400);

        e.onNext(7);
        Thread.sleep(300);
        e.onNext(8);

        Thread.sleep(300);
        e.onNext(9);

        Thread.sleep(300);
        e.onComplete();
    }
}).throttleLast(1, TimeUnit.SECONDS)//每1秒中采用数据
        .subscribe(new Observer<Integer>() {
            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, "开始采用subscribe连接");
            }

            @Override
            public void onNext(Integer value) {
                Log.d(TAG, "接收到了事件"+ value  );
            }

            @Override
            public void onError(Throwable e) {
                Log.d(TAG, "对Error事件作出响应");
            }

            @Override
            public void onComplete() {
                Log.d(TAG, "对Complete事件作出响应");
            }
        });

结果：

2022-05-05 15:27:23.124 3744-3744/com.alsan.rxjavademo D/RxFilterSymbolActivity: 开始采用subscribe连接
2022-05-05 15:27:24.129 3744-3924/com.alsan.rxjavademo D/RxFilterSymbolActivity: 接收到了事件3
2022-05-05 15:27:25.129 3744-3924/com.alsan.rxjavademo D/RxFilterSymbolActivity: 接收到了事件6
2022-05-05 15:27:26.129 3744-3924/com.alsan.rxjavademo D/RxFilterSymbolActivity: 接收到了事件9
2022-05-05 15:27:26.234 3744-3744/com.alsan.rxjavademo D/RxFilterSymbolActivity: 对Complete事件作出响应

throttleWithTimeout/debounce

Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(ObservableEmitter<Integer> e) throws Exception {
                // 隔段事件发送时间
                e.onNext(1);
                Thread.sleep(500);
                e.onNext(2); // 1和2之间的间隔小于指定时间1s，所以前1次数据（1）会被抛弃，2会被保留
                Thread.sleep(1500);  // 因为2和3之间的间隔大于指定时间1s，所以之前被保留的2事件将发出
                e.onNext(3);
                Thread.sleep(1500);  // 因为3和4之间的间隔大于指定时间1s，所以3事件将发出
                e.onNext(4);
                Thread.sleep(500); // 因为4和5之间的间隔小于指定时间1s，所以前1次数据（4）会被抛弃，5会被保留
                e.onNext(5);
                Thread.sleep(500); // 因为5和6之间的间隔小于指定时间1s，所以前1次数据（5）会被抛弃，6会被保留
                e.onNext(6);
                Thread.sleep(1500); // 因为6和Complete实践之间的间隔大于指定时间1s，所以之前被保留的6事件将发出

                e.onComplete();
            }
        }).throttleWithTimeout(1, TimeUnit.SECONDS)//每1秒中采用数据
                .subscribe(new Observer<Integer>() {
                    @Override
                    public void onSubscribe(Disposable d) {

                    }

                    @Override
                    public void onNext(Integer value) {
                        Log.d(TAG, "接收到了事件"+ value  );
                    }

                    @Override
                    public void onError(Throwable e) {
                        Log.d(TAG, "对Error事件作出响应");
                    }

                    @Override
                    public void onComplete() {
                        Log.d(TAG, "对Complete事件作出响应");
                    }
                });

结果：

2022-05-05 15:21:14.416 3428-3490/com.alsan.rxjavademo D/RxFilterSymbolActivity: 接收到了事件2
2022-05-05 15:21:15.916 3428-3490/com.alsan.rxjavademo D/RxFilterSymbolActivity: 接收到了事件3
2022-05-05 15:21:18.420 3428-3490/com.alsan.rxjavademo D/RxFilterSymbolActivity: 接收到了事件6
2022-05-05 15:21:18.920 3428-3428/com.alsan.rxjavademo D/RxFilterSymbolActivity: 对Complete事件作出响应

4. 根据"指定事件位置"过滤事件

操作符	作用
firstElement	仅选取第1个元素
lastElement	仅选取最后一个元素
elementAt	指定接收某个元素（通过索引值确定）
elementAtOrError	在elementAt（）的基础上，当出现越界情况（即获取的位置索引＞发送事件序列长度）时，即抛出异常

firstElement

Observable.just("hello", 1, "haha", 2).firstElement().subscribe((Consumer<Serializable>) serializable -> {
    Log.d(TAG, serializable.toString());
});

结果：

2022-05-05 15:38:09.536 3744-3744/com.alsan.rxjavademo D/RxFilterSymbolActivity: hello

lastElement

Observable.just("hello", 1, "haha", 2).lastElement().subscribe((Consumer<Serializable>) serializable -> {
  Log.d(TAG, serializable.toString());
});

结果：

2022-05-05 15:38:22.242 3744-3744/com.alsan.rxjavademo D/RxFilterSymbolActivity: 2

elementAt

Observable.just(1,2,2,4,4,5,6, 1).elementAt(1).subscribe(new Consumer<Integer>() {
    @Override
    public void accept(Integer integer) throws Throwable {
        Log.d(TAG, "accept:" + integer);
    }
});

结果：

2022-05-05 15:39:14.759 3744-3744/com.alsan.rxjavademo D/RxFilterSymbolActivity: accept:2

elementAtOrError

Observable.just(1,2,3,4,5).elementAtOrError(9).subscribe(new SingleObserver<Integer>() {
    @Override
    public void onSubscribe(@NonNull Disposable d) {
        Log.d(TAG, "onSubscribe...");
    }

    @Override
    public void onSuccess(@NonNull Integer integer) {
        Log.d(TAG, "onSuccess..." + integer);
    }

    @Override
    public void onError(@NonNull Throwable e) {
        Log.d(TAG, "onError:" + Log.getStackTraceString(e));
    }
});

结果：

022-05-05 15:41:16.713 4285-4285/com.alsan.rxjavademo D/RxFilterSymbolActivity: onSubscribe...
2022-05-05 15:41:16.715 4285-4285/com.alsan.rxjavademo D/RxFilterSymbolActivity: onError:java.util.NoSuchElementException
        at io.reactivex.rxjava3.internal.operators.observable.ObservableElementAtSingle$ElementAtObserver.onComplete(ObservableElementAtSingle.java:115)
        at io.reactivex.rxjava3.internal.operators.observable.ObservableFromArray$FromArrayDisposable.run(ObservableFromArray.java:112)
        at io.reactivex.rxjava3.internal.operators.observable.ObservableFromArray.subscribeActual(ObservableFromArray.java:38)
        at io.reactivex.rxjava3.core.Observable.subscribe(Observable.java:13095)
        at io.reactivex.rxjava3.internal.operators.observable.ObservableElementAtSingle.subscribeActual(ObservableElementAtSingle.java:37)
        at io.reactivex.rxjava3.core.Single.subscribe(Single.java:4813)
        at com.alsan.rxjavademo.RxFilterSymbolActivity.lambda$onCreate$17$RxFilterSymbolActivity(RxFilterSymbolActivity.java:311)
        at com.alsan.rxjavademo.-$$Lambda$RxFilterSymbolActivity$bbHK8cGk2DGgxkmEzj5endgLd8A.onClick(Unknown Source:2)
        at android.view.View.performClick(View.java:6291)
        at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:967)
        at android.view.View$PerformClick.run(View.java:24931)
        at android.os.Handler.handleCallback(Handler.java:808)
        at android.os.Handler.dispatchMessage(Handler.java:101)
        at android.os.Looper.loop(Looper.java:166)
        at android.app.ActivityThread.main(ActivityThread.java:7529)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)