RxJava 使用场景小结
jopen
9年前
取数据先检查缓存的场景
取数据，首先检查内存是否有缓存
然后检查文件缓存中是否有
最后才从网络中取
前面任何一个条件满足，就不会执行后面的
final Observable memory = Observable.create(new Observable.OnSubscribe() { @Override public void call(Subscriber super String> subscriber) { if (memoryCache != null) { subscriber.onNext(memoryCache); } else { subscriber.onCompleted(); } } }); Observable disk = Observable.create(new Observable.OnSubscribe() { @Override public void call(Subscriber super String> subscriber) { String cachePref = rxPreferences.getString("cache").get(); if (!TextUtils.isEmpty(cachePref)) { subscriber.onNext(cachePref); } else { subscriber.onCompleted(); } } }); Observable network = Observable.just("network"); //主要就是靠concat operator来实现 Observable.concat(memory, disk, network) .first() .subscribeOn(Schedulers.newThread()) .subscribe(s -> { memoryCache = "memory"; System.out.println("--------------subscribe: " + s); });finalObservablememory=Observable.create(newObservable.OnSubscribe(){ @Override publicvoidcall(SubscribersuperString>subscriber){ if(memoryCache!=null){ subscriber.onNext(memoryCache); }else{ subscriber.onCompleted(); } } }); Observable disk=Observable.create(newObservable.OnSubscribe(){ @Override publicvoidcall(SubscribersuperString>subscriber){ StringcachePref=rxPreferences.getString("cache").get(); if(!TextUtils.isEmpty(cachePref)){ subscriber.onNext(cachePref); }else{ subscriber.onCompleted(); } } }); Observable network=Observable.just("network"); //主要就是靠concat operator来实现 Observable.concat(memory,disk,network) .first() .subscribeOn(Schedulers.newThread()) .subscribe(s->{ memoryCache="memory"; System.out.println("--------------subscribe: "+s); });界面需要等到多个接口并发取完数据，再更新
//拼接两个Observable的输出，不保证顺序，按照事件产生的顺序发送给订阅者 private void testMerge() { Observable observable1 = DemoUtils.createObservable1().subscribeOn(Schedulers.newThread()); Observable observable2 = DemoUtils.createObservable2().subscribeOn(Schedulers.newThread()); Observable.merge(observable1, observable2) .subscribeOn(Schedulers.newThread()) .subscribe(System.out::println); }//拼接两个Observable的输出，不保证顺序，按照事件产生的顺序发送给订阅者 privatevoidtestMerge(){ Observableobservable1=DemoUtils.createObservable1().subscribeOn(Schedulers.newThread()); Observableobservable2=DemoUtils.createObservable2().subscribeOn(Schedulers.newThread()); Observable.merge(observable1,observable2) .subscribeOn(Schedulers.newThread()) .subscribe(System.out::println); }一个接口的请求依赖另一个API请求返回的数据
举个例子，我们经常在需要登陆之后，根据拿到的token去获取消息列表。
这里用RxJava主要解决嵌套回调的问题，有一个专有名词叫 Callback hell
NetworkService.getToken("username", "password") .flatMap(s -> NetworkService.getMessage(s)) .subscribe(s -> { System.out.println("message: " + s); });NetworkService.getToken("username","password") .flatMap(s->NetworkService.getMessage(s)) .subscribe(s->{ System.out.println("message: "+s); }); 界面按钮需要防止连续点击的情况
RxView.clicks(findViewById(R.id.btn_throttle)) .throttleFirst(1, TimeUnit.SECONDS) .subscribe(aVoid -> { System.out.println("click"); });RxView.clicks(findViewById(R.id.btn_throttle)) .throttleFirst(1,TimeUnit.SECONDS) .subscribe(aVoid->{ System.out.println("click"); });响应式的界面
比如勾选了某个checkbox，自动更新对应的preference
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this); RxSharedPreferences rxPreferences = RxSharedPreferences.create(preferences); Preference checked = rxPreferences.getBoolean("checked", true); CheckBox checkBox = (CheckBox) findViewById(R.id.cb_test); RxCompoundButton.checkedChanges(checkBox) .subscribe(checked.asAction());SharedPreferences preferences=PreferenceManager.getDefaultSharedPreferences(this); RxSharedPreferences rxPreferences=RxSharedPreferences.create(preferences); Preference checked=rxPreferences.getBoolean("checked",true); CheckBox checkBox=(CheckBox)findViewById(R.id.cb_test); RxCompoundButton.checkedChanges(checkBox) .subscribe(checked.asAction());复杂的数据变换
Observable.just("1", "2", "2", "3", "4", "5") .map(Integer::parseInt) .filter(s -> s > 1) .distinct() .take(3) .reduce((integer, integer2) -> integer.intValue() + integer2.intValue()) .subscribe(System.out::println);//9Observable.just("1","2","2","3","4","5") .map(Integer::parseInt) .filter(s->s>1) .distinct() .take(3) .reduce((integer,integer2)->integer.intValue()+integer2.intValue()) .subscribe(System.out::println);//9