Demo地址
本Demo旨在幫助從未接觸過RxJava的同學直接入坑RxJava2，如絲般順滑，萬水千山總是情，留個star行不行？
RxJava & RxAndroid （2.0版）
定義
RxJava – Reactive Extensions for the JVM – a library for composing asynchronous and event-based programs using observable sequences for the Java VM.
一個在 Java VM 上使用可觀測的序列來組成非同步的、基於事件的程式的庫
初學者如果看到這個準確但晦澀的定義肯定一臉懵逼，不過我們我們只要把握重點即可：
- 非同步
- 基於事件
- 觀察者模式
RxAndroid - Android specific bindings for RxJava 2.This module adds the minimum classes to RxJava that make writing reactive components in Android applications easy and hassle-free.
RxAndroid在RxJava的基礎上新增了最少的類使得開發Android應用中的響應式元件更加的容易和自由
特點
簡潔，並不是指程式碼量上的那種簡潔，而是邏輯上的簡潔，隨著程式邏輯變得越來越複雜，它依然能夠保持簡潔。
Github
Hello world
新增依賴
compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
compile 'io.reactivex.rxjava2:rxjava:2.0.1'複製程式碼簡單版本
//簡單版本
private void helloWorldSimple() {
//建立消費者，消費者接受一個String型別的事件
Consumer<String> consumer = new Consumer<String>() {
@Override
public void accept(String s) throws Exception {
Log.d(TAG, s);
}
};
//被觀察者發出Hello World, 並且指定該事件的消費者為consumer
Observable.just("Hello World").subscribe(consumer);
}複製程式碼執行結果
D/MainActivity: Hello World複製程式碼複雜版本
private void helloWorldComplex() {
//Observer可以看做Consumer的完整版
Observer<String> observer = new Observer<String>() {
//當Observable呼叫subscribe方法時會回撥該方法
@Override
public void onSubscribe(Disposable d) {
Log.d(TAG, "onSubscribe: ");
}
//onSubscribe方法後呼叫
@Override
public void onNext(String value) {
Log.d(TAG, "onNext: " + value);
}
//這裡沒有出錯，沒有被呼叫
@Override
public void onError(Throwable e) {
Log.d(TAG, "onError: ");
}
//onNext之後呼叫
@Override
public void onComplete() {
Log.d(TAG, "onComplete: ");
}
};
//被觀察者發出Hello World, 並且指定該事件的觀察者為observer
Observable.just("Hello World").subscribe(observer);
}複製程式碼執行結果
D/MainActivity: onSubscribe:
D/MainActivity: onNext: Hello World
D/MainActivity: onComplete: 複製程式碼變態版本
private void helloWorldPlus() {
//建立一個觀察者
Observer<String> observer = new Observer<String>() {
//當Observable呼叫subscribe方法時會回撥該方法
@Override
public void onSubscribe(Disposable d) {
Log.d(TAG, "onSubscribe: ");
}
//onSubscribe方法後呼叫
@Override
public void onNext(String value) {
Log.d(TAG, "onNext: " + value);
}
//這裡沒有出錯，沒有被呼叫
@Override
public void onError(Throwable e) {
Log.d(TAG, "onError: ");
}
//onNext之後呼叫
@Override
public void onComplete() {
Log.d(TAG, "onComplete: ");
}
};
//建立一個Observable
Observable<String> observable = Observable.create(new ObservableOnSubscribe<String>() {
@Override
public void subscribe(ObservableEmitter<String> e) throws Exception {
e.onNext("Hello World");//會呼叫到觀察者的onNext
e.onComplete();//會呼叫到觀察者的onComplete
}
});
observable.subscribe(observer);
}複製程式碼執行結果
D/MainActivity: onSubscribe:
D/MainActivity: onNext: Hello World
D/MainActivity: onComplete: 複製程式碼filter操作符
你早上去吃早餐，師傅是被觀察者，說我們這有包子，饅頭，腸粉，春捲，餃子，炒粉，你仔細想了想，發現你是最喜歡餃子的，所以把其他的都排除掉，
於是你就吃到了餃子。
private void filter() {
//把Consumer可以看做精簡版的Observer
Consumer<String> consumer = new Consumer<String>() {
//accept可以簡單的看做onNext
@Override
public void accept(String s) throws Exception {
Log.d(TAG, "accept: " + s);//這裡只能吃上餃子
}
};
Observable.just("包子", "饅頭", "腸粉", "春捲", "餃子", "炒粉")
.filter(new Predicate<String>() {
@Override
public boolean test(String s) throws Exception {
Log.d(TAG, "test: " + s);
return s.equals("餃子");//只允許餃子通過測試
}
})
.subscribe(consumer);
}複製程式碼執行結果
D/MainActivity: test: 包子
D/MainActivity: test: 饅頭
D/MainActivity: test: 腸粉
D/MainActivity: test: 春捲
D/MainActivity: test: 餃子
D/MainActivity: accept: 餃子
D/MainActivity: test: 炒粉複製程式碼map操作符
map操作符能夠完成資料型別的轉換。 以下程式碼展示了一個Student到Developer的轉換。
private void map() {
Observer<Developer> observer = new Observer<Developer>() {
@Override
public void onSubscribe(Disposable d) {
Log.d(TAG, "onSubscribe: ");
}
//觀察者接收到一個Developer
@Override
public void onNext(Developer value) {
Log.d(TAG, "onNext: " + value.toString());
}
@Override
public void onError(Throwable e) {
Log.d(TAG, "onError: ");
}
@Override
public void onComplete() {
Log.d(TAG, "onComplete: ");
}
};
Student student = new Student();
student.setName("Leon");
student.setAge(18);
//map操作符，從Student型別轉換成Developer
Observable.just(student).map(new Function<Student, Developer>() {
@Override
public Developer apply(Student student) throws Exception {
Log.d(TAG, "apply: " + student.toString());
Developer developer = new Developer();
developer.setName(student.getName());
developer.setAge(student.getAge());
developer.setSkill("Android");
return developer;
}
}).subscribe(observer);
}複製程式碼執行結果
D/MainActivity: onSubscribe:
D/MainActivity: apply: Student{name='Leon', age=18}
D/MainActivity: onNext: Developer{name='Leon', age=18, skill='Android'}
D/MainActivity: onComplete: 複製程式碼flatmap操作符
flatmap能夠鏈式地完成資料型別的轉換和加工。
遍歷一個學校中所有班級所有學生
private void flatmapClassToStudent() {
Observable.fromIterable(new School().getClasses())
//輸入是Class型別，輸出是ObservableSource<Student>型別
.flatMap(new Function<Class, ObservableSource<Student>>() {
//輸入是Class型別，輸出是ObservableSource<Student>型別
@Override
public ObservableSource<Student> apply(Class aClass) throws Exception {
Log.d(TAG, "apply: " + aClass.toString());
return Observable.fromIterable(aClass.getStudents());
}
}).subscribe(
new Observer<Student>() {
@Override
public void onSubscribe(Disposable d) {
Log.d(TAG, "onSubscribe: ");
}
@Override
public void onNext(Student value) {
Log.d(TAG, "onNext: " + value.toString());
}
@Override
public void onError(Throwable e) {
}
@Override
public void onComplete() {
}
});
}複製程式碼執行結果
D/MainActivity: onSubscribe:
D/MainActivity: apply: Class0
D/MainActivity: onNext: Student{name='Class0_0', age=18}
D/MainActivity: onNext: Student{name='Class0_1', age=18}
D/MainActivity: onNext: Student{name='Class0_2', age=18}
D/MainActivity: apply: Class1
D/MainActivity: onNext: Student{name='Class1_0', age=18}
D/MainActivity: onNext: Student{name='Class1_1', age=18}
D/MainActivity: onNext: Student{name='Class1_2', age=18}
D/MainActivity: apply: Class2
D/MainActivity: onNext: Student{name='Class2_0', age=18}
D/MainActivity: onNext: Student{name='Class2_1', age=18}
D/MainActivity: onNext: Student{name='Class2_2', age=18}複製程式碼遍歷一個學校所有班級所有組的所有學生
private void flatmapClassToGroupToStudent() {
Observable.fromIterable(new School().getClasses())
//輸入是Class型別，輸出是ObservableSource<Group>型別
.flatMap(new Function<Class, ObservableSource<Group>>() {
@Override
public ObservableSource<Group> apply(Class aClass) throws Exception {
Log.d(TAG, "apply: " + aClass.toString());
return Observable.fromIterable(aClass.getGroups());
}
})
//輸入型別是Group，輸出型別是ObservableSource<Student>型別
.flatMap(new Function<Group, ObservableSource<Student>>() {
@Override
public ObservableSource<Student> apply(Group group) throws Exception {
Log.d(TAG, "apply: " + group.toString());
return Observable.fromIterable(group.getStudents());
}
})
.subscribe(
new Observer<Student>() {
@Override
public void onSubscribe(Disposable d) {
Log.d(TAG, "onSubscribe: ");
}
@Override
public void onNext(Student value) {
Log.d(TAG, "onNext: " + value.toString());
}
@Override
public void onError(Throwable e) {
}
@Override
public void onComplete() {
}
});
}複製程式碼執行結果
D/MainActivity: onSubscribe:
D/MainActivity: apply: Class0
D/MainActivity: apply: Group0
D/MainActivity: onNext: Student{name='Group0_0', age=18}
D/MainActivity: onNext: Student{name='Group0_1', age=18}
D/MainActivity: onNext: Student{name='Group0_2', age=18}
D/MainActivity: apply: Group1
D/MainActivity: onNext: Student{name='Group1_0', age=18}
D/MainActivity: onNext: Student{name='Group1_1', age=18}
D/MainActivity: onNext: Student{name='Group1_2', age=18}
D/MainActivity: apply: Group2
D/MainActivity: onNext: Student{name='Group2_0', age=18}
D/MainActivity: onNext: Student{name='Group2_1', age=18}
D/MainActivity: onNext: Student{name='Group2_2', age=18}
D/MainActivity: apply: Class1
D/MainActivity: apply: Group0
D/MainActivity: onNext: Student{name='Group0_0', age=18}
D/MainActivity: onNext: Student{name='Group0_1', age=18}
D/MainActivity: onNext: Student{name='Group0_2', age=18}
D/MainActivity: apply: Group1
D/MainActivity: onNext: Student{name='Group1_0', age=18}
D/MainActivity: onNext: Student{name='Group1_1', age=18}
D/MainActivity: onNext: Student{name='Group1_2', age=18}
D/MainActivity: apply: Group2
D/MainActivity: onNext: Student{name='Group2_0', age=18}
D/MainActivity: onNext: Student{name='Group2_1', age=18}
D/MainActivity: onNext: Student{name='Group2_2', age=18}
D/MainActivity: apply: Class2
D/MainActivity: apply: Group0
D/MainActivity: onNext: Student{name='Group0_0', age=18}
D/MainActivity: onNext: Student{name='Group0_1', age=18}
D/MainActivity: onNext: Student{name='Group0_2', age=18}
D/MainActivity: apply: Group1
D/MainActivity: onNext: Student{name='Group1_0', age=18}
D/MainActivity: onNext: Student{name='Group1_1', age=18}
D/MainActivity: onNext: Student{name='Group1_2', age=18}
D/MainActivity: apply: Group2
D/MainActivity: onNext: Student{name='Group2_0', age=18}
D/MainActivity: onNext: Student{name='Group2_1', age=18}
D/MainActivity: onNext: Student{name='Group2_2', age=18}複製程式碼執行緒排程
關於RxJava的執行緒排程，初學者只需要掌握兩個api就夠夠的啦。
subscribeOn
指定Observable在一個指定的執行緒排程器上建立。只能指定一次，如果指定多次則以第一次為準
observeOn
指定在事件傳遞，轉換，加工和最終被觀察者接受發生在哪一個執行緒排程器。可指定多次，每次指定完都在下一步生效。
常用執行緒排程器型別
- Schedulers.single() 單執行緒排程器，執行緒可複用
- Schedulers.newThread() 為每個任務建立新的執行緒
- Schedulers.io() 處理io密集型任務，內部是執行緒池實現，可自動根據需求增長
- Schedulers.computation() 處理計算任務，如事件迴圈和回撥任務
- AndroidSchedulers.mainThread() Android主執行緒排程器
示例
private void scheduleThreads() {
Observable.create(
new ObservableOnSubscribe<String>() {
@Override
public void subscribe(ObservableEmitter<String> e) throws Exception {
Log.d(TAG, "subscribe: " + Thread.currentThread().getName());
e.onNext("Hello Leon Fan");
e.onComplete();
}
})
//指定subscribe方法在io執行緒池中呼叫
.subscribeOn(Schedulers.io())
//指定onNext方法 onComplete的方法在新建的執行緒中呼叫
.observeOn(Schedulers.newThread())
.subscribe(
new Observer<String>() {
@Override
public void onSubscribe(Disposable d) {
Log.d(TAG, "onSubscribe: " + Thread.currentThread().getName());
}
@Override
public void onNext(String value) {
Log.d(TAG, "onNext: " + Thread.currentThread().getName() + " " + value);
}
@Override
public void onError(Throwable e) {
}
@Override
public void onComplete() {
Log.d(TAG, "onComplete: " + Thread.currentThread().getName());
}
});
}複製程式碼執行結果
D/MainActivity: onSubscribe: main
D/MainActivity: subscribe: RxCachedThreadScheduler-4
D/MainActivity: onNext: RxNewThreadScheduler-1 Hello Leon Fan
D/MainActivity: onComplete: RxNewThreadScheduler-1複製程式碼如果將示例中的.observeOn(Schedulers.newThread())改成AndroidSchedulers.mainThread()，則執行結果如下：
D/MainActivity: onSubscribe: main
D/MainActivity: subscribe: RxCachedThreadScheduler-5
D/MainActivity: onNext: main Hello Leon Fan
D/MainActivity: onComplete: main複製程式碼RxJava與Retrofit整合
我們做一個Demo通過網路請求獲取豆瓣電影Top10的列表來展示RxJava和Retrofit的整合的姿勢。
Retrofit整合
新增依賴
compile 'com.squareup.retrofit2:retrofit:2.1.0'
compile 'com.squareup.retrofit2:converter-gson:2.1.0'
//compile 'com.squareup.retrofit2:adapter-rxjava:2.1.0' 官方adapter僅支援rxjava1.0
compile 'com.jakewharton.retrofit:retrofit2-rxjava2-adapter:1.0.0'複製程式碼建立網路介面
public interface Api {
@GET("top250")
Observable<MovieBean> listTop250(@Query("start") int start, @Query("count") int count);
}複製程式碼實現Api
public class MovieRetrofit {
private static MovieRetrofit sMovieRetrofit;
private final Api mApi;
public static MovieRetrofit getInstance() {
if (sMovieRetrofit == null) {
synchronized (MovieRetrofit.class) {
if (sMovieRetrofit == null) {
sMovieRetrofit = new MovieRetrofit();
}
}
}
return sMovieRetrofit;
}
private MovieRetrofit() {
Retrofit retrofit = new Retrofit.Builder().baseUrl("https://api.douban.com/v2/movie/")
.addConverterFactory(GsonConverterFactory.create())
.addCallAdapterFactory(RxJava2CallAdapterFactory.create())
.build();
mApi = retrofit.create(Api.class);
}
public Api getApi() {
return mApi;
}
}複製程式碼傳送網路請求重新整理列表
<!--新增網路許可權-->
<uses-permission android:name="android.permission.INTERNET"/>
Observable<MovieBean> movieBeanObservable = MovieRetrofit.getInstance().getApi().listTop250(0, 10);
movieBeanObservable.subscribeOn(Schedulers.io())//在io執行緒池中執行map
//將網路的結果轉換成我們要的電影名的列表
.map(new Function<MovieBean, List<String>>() {
@Override
public List<String> apply(MovieBean movieBean) throws Exception {
List<String> array = new ArrayList<String>();
for (int i = 0; i < movieBean.getSubjects().size(); i++) {
String title = movieBean.getSubjects().get(i).getTitle();
array.add(title);
}
return array;
}
})
.observeOn(AndroidSchedulers.mainThread())//在主執行緒中執行onNext
.subscribe(new Observer<List<String>>() {
......
@Override
public void onNext(List<String> value) {
ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(MovieListActivity.this, android.R.layout.simple_list_item_1, value);
setListAdapter(arrayAdapter);
}
......
});複製程式碼參考
本人旨在幫助從未接觸過RxJava的童鞋直接入坑RxJava2.0，更多使用姿勢請自行參考其他資料學習。