archived
RxJava: Windowing
- 2 minsThe window() operator is almost identical to buffer(), except that it buffers into other Observables rather than collections. This results in an Observable<Observable<T>> that emits Observables. Yielded Observables can be transformed using operators like flatMap(), concatMap(), or switchMap().
Fixed-size
The simplest overload for window() accepts a count argument:
fun main() {
Observable.range(1, 50)
.window(8)
.flatMapSingle { it.reduce("") { total, next -> "$total $next" } }
.subscribe { println("Received: $it") }
}
Received: 1 2 3 4 5 6 7 8
Received: 9 10 11 12 13 14 15 16
Received: 17 18 19 20 21 22 23 24
Received: 25 26 27 28 29 30 31 32
Received: 33 34 35 36 37 38 39 40
Received: 41 42 43 44 45 46 47 48
Received: 49 50
Just like buffer(), It’s possible to provide a skip argument:
fun main() {
Observable.range(1, 50)
.window(8, 12) // 2nd argument is skip
.flatMapSingle { it.reduce("") { total, next -> "$total $next" } }
.subscribe { println("Received: $it") }
}
Received: 1 2 3 4 5 6 7 8
Received: 13 14 15 16 17 18 19 20
Received: 25 26 27 28 29 30 31 32
Received: 37 38 39 40 41 42 43 44
Received: 49 50
Time-based
It is possible to cut-off windowed Observables at time intervals :
fun main() {
Observable.interval(300, TimeUnit.MILLISECONDS)
.map { (it + 1) * 300 } // map to elapsed time
.window(1, TimeUnit.SECONDS)
.flatMapSingle { it.reduce("") { total, next -> "$total $next" } }
.subscribe { println("Received: $it") }
TimeUnit.SECONDS.sleep(4)
}
Received: 300 600 900
Received: 1200 1500 1800
Received: 2100 2400 2700
Received: 3000 3300 3600 3900
It is also possible to specify count and timeshift arguments just like buffer() operator.
Mouaad Aallam
Software Engineer