RxJava构成

简述

RxJava = Observable + Operator + Scheduler + Observer?

截屏2021-05-10 上午11.13.55.png

Observable*

可观察数据源有哪些特征，

Usually do work when you start or stop listening
Synchronous or asynchronous
Single item,many items,or empty
Terminates with an error or succeeds to completion
May never terminate!
Just an implemention of the Observer pattern

GOTO 2016 • Exploring RxJava 2 for Android • Jake Wharton

哪些可称为可观察数据源

View事件(触摸,点击..)
网络请求返回的数据
查询数据库返回的数据
手机传感器通知数据(GPS,电量)
闹钟定时器通知...

如何创建建Observable

Observable.just("Hello")
Observable.fromArray("Hello","Hello2")
Observable.fromCallable{"Hello"}
Observable.create{ it.onNext("Hello")}
Observable.Interval(200)

Observable.create(new ObservableOnSubscribe<String>() {
	@Override
	public void subscribe(ObservableEmitter<String> emitter)  {
		emitter.onNext("Hello");
		emitter.onComplete();
	}
})

Observable.fromCallable(new Callable<String>() {
    @Override
    public String call() throws Exception {
        return "Hello";
    }
});

同时在Android使用场景中：

RxView.clicks(view) : Observable
login(@Body LoginReqParams) : Observable
RxPermissions.request(READ_PHONE_STATE) : Observable

Operator 操作符

介绍

ReactiveX的每种特定语言实现都实现了一组操作符。大致分为以下分类：

Creating Observables : create,just,from
Transforming Observables ：Map,FlatMap
Filtering Observables:Filter,Debouncee,Distinct,Skip
Combining Observables : Merge,Zip,CombineLatest
Error Handling Operators: Catch,Retry
Observable Utility Operators: Delay,TimeInterval,ObserveOn,SubscribeOn
Conditional and Boolean Operators : All,Contains,TkeWhile
Mathematical and Aggregate Operators : Average,Count,Max
Connectable Observable Operators : Connect,Replay
Operators to Convert Observables : To

map

fliter

Scheduler 线程调度

subscribeOn

指定订阅过程运行的线程，同时控制了Observable，Observer。
我们先看一段代码运行结果。

println("in main:${Thread.currentThread()}")
Observable.create<Int> {
        println("in create:${Thread.currentThread()}");
        it.onNext(1) }
	//.subscribeOn(Schedulers.newThread())
    .subscribe { println("in next  :${Thread.currentThread()} $it") }

//运行结果
in main:Thread[main,5,main]
in create:Thread[main,5,main]
in next  :Thread[main,5,main] 5

加上subscribeOn之后，发现subscribeOn的上游和下游运行线程都发生了变化。

println("in main:${Thread.currentThread()}")
Observable
    .create<Int> {
        println("in create:${Thread.currentThread()}");
        it.onNext(1) }
    .subscribeOn(Schedulers.newThread())
    .subscribe { println("in next  :${Thread.currentThread()} $it") }

//运行结果
in main:Thread[main,5,main]
in create:Thread[RxNewThreadScheduler-1,5,main]
in next  :Thread[RxNewThreadScheduler-1,5,main] 5

observeOn

指定观察者所在线程。
我们先看一段代码运行结果。

println("in main:${Thread.currentThread()}")
Observable
    .create<Int> {
        println("in create:${Thread.currentThread()}");
        it.onNext(1) }
  //.observeOn(Schedulers.newThread())
    .subscribe { println("int next  :${Thread.currentThread()} $it") }

//运行结果
in main:Thread[main,5,main]
in create:Thread[main,5,main]
in next  :Thread[main,5,main] 5

加上observeOn之后，发现observeOn下游运行线程都发生了变化。

println("in main:${Thread.currentThread()}")
Observable.create<Int> {
        println("in create:${Thread.currentThread()}");
        it.onNext(1) }
	.observeOn(Schedulers.newThread())
    .subscribe { println("in next  :${Thread.currentThread()} $it") }
//运行结果
in main:Thread[main,5,main]
in create:Thread[main,5,main]
in next  :Thread[RxNewThreadScheduler-1,5,main] 5

特别的是：

Observer 观察者

略

APP中使用场景

列举目前我们App中使用到RxJava的场景。

网络请求:Retrofit+RxJava

@POST("/content/user/info")
Observable<BaseResponse<UserInfo>> userInfo_Ob(@Body UserInfoReq req);

这里有一段我们使用操作符的代码，app初始化时同步服务端数据

//app初始化时同步服务端数据,
fun checkRequiredObservable(): Observable<PersonRequiredInfo> {
    	//后续需要的个人信息
        var personRequiredInfo = PersonRequiredInfo()
        val allObservables = arrayListOf(
                ...
            	//一系列独立的请求
                appTabSetting(),//底部tab配置
            	userInfoObservable(),//用户信息
                queryBindConfig(),//用户绑定账号信息
                syncBabyInfoObservable(userId) //同步宝宝信息
                ...
        )
         var zipObservable =  Observable.zip(allObservables) { 
             return@zip personRequiredInfo 
         }
        return apolloAppConfig()//先获取apollo配置信息，同时保存配置
                .flatMap {zipObservable } //并行上面一系列请求
                .onErrorReturn { personRequiredInfo }
                .doOnNext {registerUserSuperProperties()}
                .compose(RxHelper.io2MainThread())
}
private fun syncBabyInfoObservable(): Observable<Any> {
        return getBabyInfoObservable() //先获取服务端宝宝信息
            .flatMap { updateBabyInfoObservable() } //本地与服务端比较，如果需要上传则上传
            .flatMap { getBabyInfoObservable().map { Any() } }//再次获取同步后的宝宝信息
            .onErrorReturn { Any()}
}

现有接口状况的情况下，很难想象，如果没有RxJava我该如何组合这些请求。

截屏2021-05-10 下午4.27.31.png

防抖(debounce)与节流(throttle)

debounce

Returns an Observable that mirrors the source ObservableSource, except that it drops items emitted by the source ObservableSource that are followed by newer items before a timeout value expires. The timer resets on each emission.

throttleFirst

Returns an Observable that emits only the first item emitted by the source ObservableSource during sequential time windows of a specified duration.

View重复点击

RxView.clicks(container)
    .throttleFirst(800,TimeUnit.MILLISECONDS)
    .subscribe { onclick() }

搜索防抖

RxTextView.textChanges(etSearch)
    .debounce(searchDebounceTime, TimeUnit.MILLISECONDS)
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe { goSearch(chars) }

页面刷新频率控制

class RefreshDebounce {
    private var rxEmitter: ObservableEmitter<Long>? = null
    private var observable = Observable
        .create<Long> { rxEmitter = it }
        .debounce(1000L, TimeUnit.MILLISECONDS)

    constructor(consumer: (Long) -> Unit? ){
        observable.subscribe { consumer.invoke(it) }
    }
    fun callRefresh() = rxEmitter?.onNext(System.currentTimeMillis())
}

//使用
var refreshDebounce = RefreshDebounce { println("refresh:$it") }
refreshDebounce.callRefresh()

定时/延时执行

private void startCountDown15Min() {
    countDown15MinDisposable = Observable.timer(900, TimeUnit.SECONDS)
           subscribe(aLong -> Log.i(TAG, "倒计时时间到"));
}

private void cancelCountDown15Min() {
    if (countDown15MinDisposable != null && !countDown15MinDisposable.isDisposed()) {
        countDown15MinDisposable.dispose();
    }
}

系统权限申请

new RxPermissions(activity)
	.request(Manifest.permission.READ_PHONE_STATE)
    .subscribe(aBoolean -> Log.d(TAG,"result:"+aBoolean)

RxJava介绍2：基本结构和使用场景