Rxjava操作符2：concat

说明：

concat 将两个及以上的可观察者，进行有序的发射

Concatenates elements of each ObservableSource provided via an Iterable sequence into a single sequence
of elements without interleaving them.

方法预览：

//接收一个可观察者
public static <T> Observable<T> concat(ObservableSource<? extends ObservableSource<? extends T>> sources)
//接收两个可观察者
public static <T> Observable<T> concat(ObservableSource<? extends T> source1, ObservableSource<? extends T> source2)
//接收三个可观察者
public static <T> Observable<T> concat(ObservableSource<? extends T> source1, ObservableSource<? extends T> source2, ObservableSource<? extends T> source3)
//接收四个可观察者
public static <T> Observable<T> concat(ObservableSource<? extends T> source1, ObservableSource<? extends T> source2,ObservableSource<? extends T> source3, ObservableSource<? extends T> source4)
//接收一个集合，如arrylist
public static <T> Observable<T> concat(Iterable<? extends ObservableSource<? extends T>> sources)

从重载的方法可以看出，concat可以接收1到4个可观察者，或者一个可观察者的集合

例子1：

public void concat(View view){
        Observable observable1 = Observable.just(1,2,3,4,5,6);
        Observable observable2 = Observable.just(7,8);
        ArrayList list = new ArrayList();
        Observable.concat(list)
                .subscribe(new Observer() {
                    @Override
                    public void onSubscribe(Disposable d) {
                        Log.e("RxTest","onSubscribe");
                    }

                    @Override
                    public void onNext(Object o) {
                        Log.e("RxTest","onNext "+(int)o);
                    }

                    @Override
                    public void onError(Throwable e) {
                        Log.e("RxTest","onError "+e.getMessage().toString());
                    }

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

打印结果：

onSubscribe
onNext 1
onNext 2
onNext 3
onNext 4
onNext 5
onNext 6
onNext 7
onNext 8
onComplete

可以看到发射的数据有序的，如果需要在数据全部发射完，再执行某个动作，可以在onComplete()方法中。

例子2，使用Arrylist传递：

    public void concat1(View view){
        ArrayList<Observable<Integer>> list = new ArrayList<>();
        Observable observable1 = Observable.just(1,2);
        Observable observable2 = Observable.just(3,4);
        Observable observable3 = Observable.just(5,6);
        Observable observable4 = Observable.just(7,8);
        Observable observable5 = Observable.just(9,10);
        list.add(observable1);
        list.add(observable2);
        list.add(observable3);
        list.add(observable4);
        list.add(observable5);
        Observable.concat(list)
                .subscribe(new Consumer<Integer>() {
                    @Override
                    public void accept(Integer o) throws Exception {
                        Log.e("RxTest","accept "+o);
                    }
                });
    }

打印结果：

accept 1
accept 2
accept 3
accept 4
accept 5
accept 6
accept 7
accept 8
accept 9
accept 10