Rxjava2 filter

filter的作用就是过滤出指定的数据 例子中我们只要数据大于4的数据。

Observable.just(1, 2, 3, 4, 5).filter(new Predicate<Integer>() {
            @Override
            public boolean test(@NotNull Integer integer) throws Exception {
                return integer > 4;
            }
        }).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                System.out.println(integer);
            }
        });

  public final Observable<T> filter(Predicate<? super T> predicate) {
        ObjectHelper.requireNonNull(predicate, "predicate is null");
        return RxJavaPlugins.onAssembly(new ObservableFilter<T>(this, predicate));
    }

public final class ObservableFilter<T> extends AbstractObservableWithUpstream<T, T> {
    final Predicate<? super T> predicate;
    public ObservableFilter(ObservableSource<T> source, Predicate<? super T> predicate) {
        super(source);
        this.predicate = predicate;
    }

    @Override
    public void subscribeActual(Observer<? super T> observer) {
        source.subscribe(new FilterObserver<T>(observer, predicate));
    }

    static final class FilterObserver<T> extends BasicFuseableObserver<T, T> {
        final Predicate<? super T> filter;

        FilterObserver(Observer<? super T> actual, Predicate<? super T> filter) {
            super(actual);
            this.filter = filter;
        }

        @Override
        public void onNext(T t) {
            if (sourceMode == NONE) {
                boolean b;
                try {
                     //测试通过
                    b = filter.test(t);
                } catch (Throwable e) {
                    fail(e);
                    return;
                }
                if (b) {
                    //测试通过的数据可以发出
                    downstream.onNext(t);
                }
            } else {
                downstream.onNext(null);
            }
        }

     ...
    }
}