RxJava2轻松入门

时间  2019-11-16
标签 rxjava2 rxjava 轻松 入门 栏目 Java 繁體版
原文   原文链接

Demo地址

RxJava2Demojavascript

本Demo旨在帮助从未接触过RxJava的同窗直接入坑RxJava2，如丝般顺滑，万水千山老是情，留个star行不行？java

RxJava & RxAndroid （2.0版）

定义

RxJava – Reactive Extensions for the JVM – a library for composing asynchronous and event-based programs using observable sequences for the Java VM.react

一个在 Java VM 上使用可观测的序列来组成异步的、基于事件的程序的库android

初学者若是看到这个准确但晦涩的定义确定一脸懵逼，不过咱们咱们只要把握重点便可：git

  • 异步
  • 基于事件
  • 观察者模式

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.github

RxAndroid在RxJava的基础上添加了最少的类使得开发Android应用中的响应式组件更加的容易和自由api

特色

简洁，并非指代码量上的那种简洁，而是逻辑上的简洁，随着程序逻辑变得愈来愈复杂，它依然可以保持简洁。网络

Github

Hello world

添加依赖

compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
compile 'io.reactivex.rxjava2:rxjava:2.0.1'复制代码

简单版本

//简单版本
private void helloWorldSimple() {
    //建立消费者，消费者接受一个String类型的事件
    Consumer<String> consumer = new Consumer<String>() {
        @Override
        public void accept(String s) throws Exception {
            Log.d(TAG, s);
        }
    };
    //被观察者发出Hello World, 而且指定该事件的消费者为consumer
    Observable.just("Hello World").subscribe(consumer);
}复制代码

运行结果

D/MainActivity: Hello World复制代码

复杂版本

private void helloWorldComplex() {
    //Observer能够看作Consumer的完整版
    Observer<String> observer = new Observer<String>() {

        //当Observable调用subscribe方法时会回调该方法
        @Override
        public void onSubscribe(Disposable d) {
            Log.d(TAG, "onSubscribe: ");
        }

        //onSubscribe方法后调用
        @Override
        public void onNext(String value) {
            Log.d(TAG, "onNext: " + value);
        }
        //这里没有出错，没有被调用
        @Override
        public void onError(Throwable e) {
            Log.d(TAG, "onError: ");
        }

        //onNext以后调用
        @Override
        public void onComplete() {
            Log.d(TAG, "onComplete: ");
        }
    };
    //被观察者发出Hello World, 而且指定该事件的观察者为observer
    Observable.just("Hello World").subscribe(observer);
}复制代码

运行结果

D/MainActivity: onSubscribe: 
D/MainActivity: onNext: Hello World
D/MainActivity: onComplete: 复制代码

变态版本

private void helloWorldPlus() {
    //建立一个观察者
    Observer<String> observer = new Observer<String>() {

        //当Observable调用subscribe方法时会回调该方法
        @Override
        public void onSubscribe(Disposable d) {
            Log.d(TAG, "onSubscribe: ");
        }

        //onSubscribe方法后调用
        @Override
        public void onNext(String value) {
            Log.d(TAG, "onNext: " + value);
        }
        //这里没有出错，没有被调用
        @Override
        public void onError(Throwable e) {
            Log.d(TAG, "onError: ");
        }

        //onNext以后调用
        @Override
        public void onComplete() {
            Log.d(TAG, "onComplete: ");
        }
    };

    //建立一个Observable
    Observable<String> observable = Observable.create(new ObservableOnSubscribe<String>() {

        @Override
        public void subscribe(ObservableEmitter<String> e) throws Exception {
            e.onNext("Hello World");//会调用到观察者的onNext
            e.onComplete();//会调用到观察者的onComplete
        }
    });

    observable.subscribe(observer);
}复制代码

运行结果

D/MainActivity: onSubscribe: 
D/MainActivity: onNext: Hello World
D/MainActivity: onComplete: 复制代码

filter操做符

你早上去吃早餐，师傅是被观察者，说咱这有包子，馒头，肠粉，春卷，饺子，炒粉，你仔细想了想，发现你是最喜欢饺子的，因此把其余的都排除掉，
因而你就吃到了饺子。app

private void filter() {
    //把Consumer能够看作精简版的Observer
    Consumer<String> consumer = new Consumer<String>() {
        //accept能够简单的看作onNext
        @Override
        public void accept(String s) throws Exception {
            Log.d(TAG, "accept: " + s);//这里只能吃上饺子
        }
    };

    Observable.just("包子", "馒头", "肠粉", "春卷", "饺子", "炒粉")
            .filter(new Predicate<String>() {
                @Override
                public boolean test(String s) throws Exception {
                    Log.d(TAG, "test: " + s);
                    return s.equals("饺子");//只容许饺子经过测试
                }
            })
            .subscribe(consumer);
}复制代码

运行结果

D/MainActivity: test: 包子
D/MainActivity: test: 馒头
D/MainActivity: test: 肠粉
D/MainActivity: test: 春卷
D/MainActivity: test: 饺子
D/MainActivity: accept: 饺子
D/MainActivity: test: 炒粉复制代码

map操做符

map操做符可以完成数据类型的转换。 如下代码展现了一个Student到Developer的转换。异步

private void map() {
    Observer<Developer> observer = new Observer<Developer>() {
        @Override
        public void onSubscribe(Disposable d) {
            Log.d(TAG, "onSubscribe: ");
        }

        //观察者接收到一个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操做符，从Student类型转换成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);
}复制代码

运行结果

D/MainActivity: onSubscribe: 
D/MainActivity: apply: Student{name='Leon', age=18}
D/MainActivity: onNext: Developer{name='Leon', age=18, skill='Android'}
D/MainActivity: onComplete: 复制代码

flatmap操做符

flatmap可以链式地完成数据类型的转换和加工。

遍历一个学校中全部班级全部学生

private void flatmapClassToStudent() {

    Observable.fromIterable(new School().getClasses())

            //输入是Class类型，输出是ObservableSource<Student>类型
            .flatMap(new Function<Class, ObservableSource<Student>>() {

                //输入是Class类型，输出是ObservableSource<Student>类型
                @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() {

                }
            });
}复制代码

运行结果

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}复制代码

遍历一个学校全部班级全部组的全部学生

private void flatmapClassToGroupToStudent() {
    Observable.fromIterable(new School().getClasses())
            //输入是Class类型，输出是ObservableSource<Group>类型
            .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());
                }
            })
            //输入类型是Group，输出类型是ObservableSource<Student>类型
            .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() {

                        }
                    });
}复制代码

运行结果

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}复制代码

线程调度

关于RxJava的线程调度，初学者只须要掌握两个api就够够的啦。

subscribeOn

指定Observable在一个指定的线程调度器上建立。只能指定一次，若是指定屡次则以第一次为准

observeOn

指定在事件传递，转换，加工和最终被观察者接受发生在哪个线程调度器。可指定屡次，每次指定完都在下一步生效。

经常使用线程调度器类型

  • Schedulers.single() 单线程调度器，线程可复用
  • Schedulers.newThread() 为每一个任务建立新的线程
  • Schedulers.io() 处理io密集型任务，内部是线程池实现，可自动根据需求增加
  • Schedulers.computation() 处理计算任务，如事件循环和回调任务
  • AndroidSchedulers.mainThread() Android主线程调度器

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线程池中调用
            .subscribeOn(Schedulers.io())
            //指定onNext方法 onComplete的方法在新建的线程中调用
            .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());
                        }
                    });

}复制代码

运行结果

D/MainActivity: onSubscribe: main
D/MainActivity: subscribe: RxCachedThreadScheduler-4
D/MainActivity: onNext: RxNewThreadScheduler-1 Hello Leon Fan
D/MainActivity: onComplete: RxNewThreadScheduler-1复制代码

若是将示例中的.observeOn(Schedulers.newThread())改为AndroidSchedulers.mainThread()，则运行结果以下：

D/MainActivity: onSubscribe: main
D/MainActivity: subscribe: RxCachedThreadScheduler-5
D/MainActivity: onNext: main Hello Leon Fan
D/MainActivity: onComplete: main复制代码

RxJava与Retrofit集成

咱们作一个Demo经过网络请求获取豆瓣电影Top10的列表来展现RxJava和Retrofit的集成的姿式。

Retrofit集成

添加依赖

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仅支持rxjava1.0
compile 'com.jakewharton.retrofit:retrofit2-rxjava2-adapter:1.0.0'复制代码

建立网络接口

public interface Api {
    @GET("top250")
    Observable<MovieBean> listTop250(@Query("start") int start, @Query("count") int count);
}复制代码

实现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;
    }
}复制代码

发送网络请求刷新列表

<!--添加网络权限-->
<uses-permission android:name="android.permission.INTERNET"/>

Observable<MovieBean> movieBeanObservable = MovieRetrofit.getInstance().getApi().listTop250(0, 10);
movieBeanObservable.subscribeOn(Schedulers.io())//在io线程池中执行map
        //将网络的结果转换成咱们要的电影名的列表
        .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())//在主线程中执行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);
            }
            ......
        });复制代码

参考

本人旨在帮助从未接触过RxJava的童鞋直接入坑RxJava2.0，更多使用姿式请自行参考其余资料学习。

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