參考:
http://blog.csdn.net/maplejaw_/article/details/52442065
http://www.itdecent.cn/nb/5864063
去年RxJava2.x發(fā)布了,與RxJava1.x相比,使用上有不少改動(只是API函數名改了,而使用流程思維不變),故在此記錄筆記存檔!
一.基本用法
1.創(chuàng)建Observable(被觀察者/發(fā)布者/發(fā)射者)
(1)create()
Observable observable = Observable.create(new ObservableOnSubscribe<String>() {
@Override
public void subscribe(@NonNull ObservableEmitter<String> observableEmitter) throws Exception {
observableEmitter.onNext("發(fā)布數據1");
observableEmitter.onNext("發(fā)布數據2");
observableEmitter.onError(new Throwable("發(fā)生錯誤"));
observableEmitter.onComplete(); //完成
}
});
(2)just
Observable observable = Observable.just("發(fā)布數據1", "發(fā)布數據2");
(3)fromIterable, fromArray
ArrayList<String> list = new ArrayList<>();
list.add("發(fā)布數據1");
list.add("發(fā)布數據2");
Observable observable = Observable.fromIterable(list);
(4)range,第一個參數為起始值,第二個為發(fā)送的個數,如果為0則不發(fā)送,負數則拋異常
Observable observable = Observable.range(10, 5)
(5)defer,延期,有觀察者訂閱時才創(chuàng)建Observable
Observable observable = Observable.defer(new Callable<ObservableSource>() {
@Override
public ObservableSource call() throws Exception {
return Observable.just("發(fā)布數據1","發(fā)布數據2");
}
});
(6)interval,定時周期發(fā)布數據
Observable observable = Observable.interval(500, TimeUnit.MILLISECONDS); //周期500ms
(7)timer,延遲發(fā)布數據
Observable observable = Observable.timer(300, TimeUnit.MILLISECONDS); //延遲300ms
(8)repeat,重復發(fā)布數據
Observable observable = Observable.just("發(fā)布數據1").repeat(3); //重復發(fā)布3次
2.創(chuàng)建Observer(觀察者/訂閱者/接收者)
(1).Observer完整形式
Observer observer = new Observer() {
@Override
public void onSubscribe(@NonNull Disposable disposable) {
//Disposable 相當于RxJava1.x中的Subscription,用于解除訂閱
}
@Override
public void onNext(@NonNull Object o) {
//接收數據
}
@Override
public void onError(@NonNull Throwable throwable) {
//接收錯誤
}
@Override
public void onComplete() {
//通知完成
}
};
(2).Observer簡寫形式
Consumer onNext = new Consumer() {//接收數據
@Override
public void accept(Object o) throws Exception {
}
};
Consumer<Throwable> onError = new Consumer<Throwable>() {//接收錯誤
@Override
public void accept(Throwable throwable) throws Exception {
}
};
Action onComplete = new Action() {//通知完成
@Override
public void run() throws Exception {
}
};
Consumer<Disposable> onSubscribe = new Consumer<Disposable>() {
@Override
public void accept(Disposable disposable) throws Exception {
}
};
3.Observer訂閱Observable
(1).Observer完整訂閱
observable.subscribe(observer); //訂閱
(2).Observer簡寫訂閱
observable.subscribe(onNext);
observable.subscribe(onNext, onError);
observable.subscribe(onNext, onError, onComplete);
observable.subscribe(onNext, onError, onComplete, onSubscribe);
二.線程調度
調度器類型
Schedulers.computation(?) 用于計算任務,如事件循環(huán)或和回調處理,不要用于IO操作(IO操作請使用Schedulers.io());默認線程數等于處理器的數量
Schedulers.from(executor) 使用指定的Executor作為調度器
Schedulers.io(?) 用于IO密集型任務,如異步阻塞IO操作,這個調度器的線程池會根據需要增長;
對于普通的計算任務,請使用Schedulers.computation();
Schedulers.io(?)默認是一個CachedThreadScheduler,很像一個有線程緩存的新線程調度器
Schedulers.newThread(?) 為每個任務創(chuàng)建一個新線程
Schedulers.trampoline(?) 當其它排隊的任務完成后,在當前線程排隊開始執(zhí)行
AndroidSchedulers.mainThread() 此調度器為RxAndroid特有,顧名思義,運行在Android UI線程上
Observable.just("耗時操作...")
.subscribeOn(Schedulers.io())//io線程-發(fā)布者
.observeOn(AndroidSchedulers.mainThread())//主線程-接收者
.subscribe(new Consumer<String>() {
@Override
public void accept(String s) throws Exception {
}
});
三.常用操作符
1.map-數據類型轉換
Observable.just("123")
.map(new Function<String, Integer>() {
@Override
public Integer apply(@NonNull String s) throws Exception {
return Integer.parseInt(s);
}
})
.subscribe(new Consumer<Integer>() {
@Override
public void accept(Integer integer) throws Exception {
System.out.println(integer);
}
});
2.flatMap-數據集合扁平化(遍歷循環(huán)每一個元素)
List<String> list = new ArrayList<>();
list.add("1");
list.add("2");
list.add("3");
List<List<String>> listSSS = new ArrayList<>();//二維數組集合
listSSS.add(list);
Observable.fromIterable(listSSS)
.flatMap(new Function<List<String>, ObservableSource<String>>() {
@Override
public ObservableSource<String> apply(@NonNull List<String> list) throws Exception {
return Observable.fromIterable(list);
}
})
.subscribe(new Consumer<String>() {
@Override
public void accept(String s) throws Exception {
System.out.println(s);
}
});
3.buffer-緩存滿后,以list集合發(fā)送數據
List<String> list = new ArrayList<>();
list.add("1");
list.add("2");
list.add("3");
Observable.fromIterable(list)
.buffer(list.size()) //緩存一起發(fā)送
.subscribe(new Consumer<List<String>>() {
@Override
public void accept(List<String> list) throws Exception {
System.out.println(list.size());
}
});
4.take(n)-發(fā)送前n項數據
Observable.just(1, 2, 1, 1, 2, 3)
.take(3) //發(fā)送前3項數據
.subscribe(new Consumer<Integer>() {
@Override
public void accept(Integer integer) throws Exception {
System.out.println(integer);
}
});
5.distinct-去除重復項
Observable.just(1, 2, 1, 1, 2, 3)
.distinct() //去重
.subscribe(new Consumer<Integer>() {
@Override
public void accept(Integer integer) throws Exception {
System.out.println(integer);
}
});
6.filter-過濾
Observable.just(1, 2, 3, 4, 5)
.filter(new Predicate<Integer>() {
@Override
public boolean test(@NonNull Integer integer) throws Exception {
return integer > 3; //過濾大于3
}
})
.subscribe(new Consumer<Integer>() {
@Override
public void accept(Integer integer) throws Exception {
System.out.println(integer);
}
});
五.Flowable-背壓
Flowable是RxJava2.x中新增的類,專門用于應對背壓Backpressure問題
背壓: 即生產者的速度大于消費者的速度帶來的問題,比如在Android中常見的點擊事件,點擊過快則會造成點擊兩次的效果!
Flowable.create(new FlowableOnSubscribe<Integer>() {
@Override
public void subscribe(FlowableEmitter<Integer> e) throws Exception {
for (int i = 0; i < 10000; i++)
e.onNext(i);
e.onComplete();
}
}, BackpressureStrategy.ERROR) //指定背壓處理策略,拋出異常錯
.subscribeOn(Schedulers.computation())
.observeOn(Schedulers.newThread())
.subscribe(new Consumer<Integer>() {
@Override
public void accept(Integer integer) throws Exception {
System.out.println(integer);
Thread.sleep(1000);
}
}, new Consumer<Throwable>() {
@Override
public void accept(Throwable throwable) throws Exception {
System.out.println(throwable);
}
});
// 如Rxjava1.x一樣簡寫
Flowable.range(1,10000)
.onBackpressureDrop() // 背壓
.subscribe(new Consumer<Integer>() {
@Override
public void accept(Integer integer) throws Exception {
System.out.println(integer);
}
});
四.Subject
Subject extends Observable implements Observe
作用:
可充當Observable
可充當Observer
是Observable和Observer之間的橋梁
Subject有四個實現類: AsyncSubject, BehaviorSubject, PublishSubject, ReplaySubject
注意:
從多個線程中調用onNext(on系列方法),需要使用串行化Serialized,才能順序調用!
SerializedSubject<String, Integer> ser = new SerializedSubject(publishSubject);
Processor和Subject的作用相同,其中Processor是RxJava2.x新增的,繼承自Flowable,所以支持背壓控制
//Processor
AsyncProcessor<String> processor = AsyncProcessor.create();
processor.subscribe(o -> Log.d("JG",o)); //three
processor.onNext("one");
processor.onNext("two");
processor.onNext("three");
processor.onComplete();
1.AsyncSubject只接收onCompleted()被調用前的最后一個數據
AsyncSubject<String> asyncSubject = AsyncSubject.create();
asyncSubject.onNext("asyncSubject1");
asyncSubject.onNext("asyncSubject2");
asyncSubject.onNext("asyncSubject3");
asyncSubject.onComplete();
asyncSubject.subscribe(new Consumer<String>() {
@Override
public void accept(String s) throws Exception {
System.out.println(s);//只接收到asyncSubject3
}
});
2.BehaviorSubject接收被訂閱前的最后一個數據,還接收訂閱后的數據
BehaviorSubject<String> behaviorSubject = BehaviorSubject.create();
behaviorSubject.onNext("behaviorSubject1");
behaviorSubject.onNext("behaviorSubject2");
behaviorSubject.subscribe(new Consumer<String>() {
@Override
public void accept(String s) throws Exception {
System.out.println(s); //接收到behaviorSubject2, behaviorSubject3, behaviorSubject4
}
});
behaviorSubject.onNext("behaviorSubject3");
behaviorSubject.onNext("behaviorSubject4");
3.PublishSubject只接收被訂閱后的數據
PublishSubject<String> publishSubject = PublishSubject.create();
publishSubject.onNext("publishSubject1");
publishSubject.onNext("publishSubject2");
publishSubject.subscribe(new Consumer<String>() {
@Override
public void accept(String s) throws Exception {
System.out.println(s);只接收到behaviorSubject3, behaviorSubject4
}
});
publishSubject.onNext("publishSubject3");
publishSubject.onNext("publishSubject4");
4.ReplaySubject接收所有數據,無論何時訂閱! 但緩存到一定大小時或一段時間后會丟棄舊的數據!
ReplaySubject<String> replaySubject = ReplaySubject.create(); //默認初始緩存容量大小為16
//replaySubject = ReplaySubject.create(100);//指定初始緩存容量大小為100
//replaySubject = ReplaySubject.createWithSize(2);//只緩存訂閱前最后2條數據
//replaySubject = ReplaySubject.createWithTime(1,TimeUnit.SECONDS,Schedulers.computation());//只緩存被訂閱前1秒內的數據
replaySubject.onNext("replaySubject:pre1");
replaySubject.onNext("replaySubject:pre2");
replaySubject.onNext("replaySubject:pre3");
replaySubject.subscribe(new Consumer<String>() {
@Override
public void accept(String s) throws Exception {
System.out.println(s);
}
});
replaySubject.onNext("replaySubject:after1");
replaySubject.onNext("replaySubject:after2");
5.Subject作為橋梁,使用示例
//1.Subject作為橋梁
Subject<String> subject = BehaviorSubject.create();
//2.訂閱
subject.subscribe(new Consumer<String>() {
@Override
public void accept(String s) throws Exception {
System.out.println(s);
}
});
//3.發(fā)布數據
Observable.create(new ObservableOnSubscribe<String>() {
@Override
public void subscribe(@NonNull ObservableEmitter<String> observableEmitter) throws Exception {
observableEmitter.onNext("as Bridge");
}
}).subscribe(subject);
簡書: http://www.itdecent.cn/p/724c937e3d0c
CSDN博客: http://blog.csdn.net/qq_32115439/article/details/78090944
GitHub博客: http://lioil.win/2017/09/25/JavaSE-RxJava.html
Coding博客: http://c.lioil.win/2017/09/25/JavaSE-RxJava.html