Android RxJava1.X升级到RxJava2.X笔记

简书地址 http://www.jianshu.com/p/2badfbb3a33b

描述	RxJava 1.X	RxJava 2.X
package包名	rx.xxx	io.reactivex.xxx
Reactive Streams规范	1.X早于Reactive Streams规范出现，仅部分支持规范	完全支持
Backpressure 背压	对背压的支持不完善	Observable设计为不支持背压 新增Flowable支持背压
null空值	支持	不再支持null值，传入null值会抛出 NullPointerException
Schedulers线程调度器	Schedulers.immediate() Schedulers.trampoline() Schedulers.computation() Schedulers.newThread() Schedulers.io() Schedulers.from(executor) AndroidSchedulers.mainThread()	移除Schedulers.immediate() 新增Schedulers.single() 其它未变
Single	行为类似Observable，但只会发射一个onSuccess或onError	按照Reactive Streams规范重新设计，遵循协议onSubscribe(onSuccess/onError)
Completable	行为类似Observable，要么全部成功，要么就失败	按照Reactive Streams规范重新设计，遵循协议onSubscribe (onComplete/onError)
Maybe	无	2.X新增，行为类似Observable，可能会有一个数据或一个错误，也可能什么都没有。可以将其视为一种返回可空值的方法。这种方法如果不抛出异常的话，将总是会返回一些东西，但是返回值可能为空，也可能不为空。按照Reactive Streams规范设计，遵循协议onSubscribe (onSuccess/onError/onComplete)
Flowable	无	2.X新增，行为类似Observable，按照Reactive Streams规范设计，支持背压Backpressure
Subject	AsyncSubject BehaviorSubject PublishSubject ReplaySubject UnicastSubject	2.X依然维护这些Subject现有的功能，并新增： AsyncProcessor BehaviorProcessor PublishProcessor ReplayProcessor UnicastProcessor 支持背压Backpressure
Subscriber	Subscriber	由于与Reactive Streams的命名冲突，Subscriber已重命名为Disposable

RxJava 2.X + Retrofit + OkHttp 简单示例点这里

library依赖变化

//1.X
compile 'io.reactivex:rxjava:1.2.1'
compile 'io.reactivex:rxandroid:1.2.1'

//2.X
compile 'io.reactivex.rxjava2:rxjava:2.0.0'
compile 'io.reactivex.rxjava2:rxandroid:2.0.0'

package变化

变动主要为rx.xxx --> io.reactivex.xxx

//1.X
import rx.Observable;
import rx.Subscription;
import rx.android.schedulers.AndroidSchedulers;
import rx.schedulers.Schedulers;
import rx.functions.Action1;

//2.X
import io.reactivex.Observable;
import io.reactivex.ObservableSource;
import io.reactivex.ObservableTransformer;
import io.reactivex.disposables.Disposable;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.schedulers.Schedulers;
import io.reactivex.functions.Consumer;

null值

RxJava 2.X不再支持null值，如果传入一个null会抛出NullPointerException

Observable.just(null);

Single.just(null);

Observable.fromCallable(() -> null)
    .subscribe(System.out::println, Throwable::printStackTrace);

Observable.just(1).map(v -> null)
    .subscribe(System.out::println, Throwable::printStackTrace);

案例1

//1.X
public static final Observable.Transformer IO_TRANSFORMER = new Observable.Transformer() {
    @Override public Object call(Object observable) {
        return ((Observable) observable).subscribeOn(Schedulers.io())
                                        .unsubscribeOn(Schedulers.io())
                                        .observeOn(Schedulers.io());
    }
};
public static final <T> Observable.Transformer<T, T> applySchedulers(Observable.Transformer transformer){
    return (Observable.Transformer<T, T>)transformer;
}
Action1<Integer> onNext = null;
String[] items = { "item1", "item2", "item3" };
Subscription subscription = Observable.from(items)
                                      .compose(RxUtil.<String>applySchedulers(IO_TRANSFORMER))
                                      .map(new Func1<String, Integer>() {
                                                  @Override public Integer call(String s) {
                                                      return Integer.valueOf(s);
                                                  }
                                              })
                                      .subscribe(onNext);
//TODO subscription.unsubscribe();   

//2.X
public static final ObservableTransformer IO_TRANSFORMER = new ObservableTransformer() {
    @Override public ObservableSource apply(Observable upstream) {
        return upstream.subscribeOn(Schedulers.io())
                       .unsubscribeOn(Schedulers.io())
                       .observeOn(Schedulers.io());
    }
};
public static final <T> ObservableTransformer<T, T> applySchedulers(ObservableTransformer transformer){
    return (ObservableTransformer<T, T>)transformer;
}
Consumer<Integer> onNext = null;
String[] items = { "item1", "item2", "item3" };
Disposable disposable = Observable.fromArray(items)
                                  .compose(RxUtil.<String>applySchedulers(IO_TRANSFORMER))
                                  .map(new Function<String, Integer>() {
                                              @Override public Integer apply(String s) throws Exception {
                                                  return Integer.valueOf(s);
                                              }
                                          })
                                  .subscribe(onNext);
//TODO disposable.dispose();

• .subscribe(...)返回值的变化:1.X为Subscription, 2.X为Disposable
• Transformer的变化:1.X为rx.Observable内部的Transformer接口, 继承自Func1<Observable<T>, Observable<R>>, 2.X为io.reactivexObservableTransformer<Upstream, Downstream>,是一个独立的接口
• AndroidSchedulers的变化: 1.X为rx.android.schedulers.AndroidSchedulers, 2.X为io.reactivex.android.schedulers.AndroidSchedulers
• Func1的变化: 1.X为rx.functions.Func1, 2.X为io.reactivex.functions.Function
• 其它重载方法见下方截图 
   
  
案例2

//1.X
public class AppBaseActivity extends AppCompatActivity {
    ...
    private CompositeSubscription mCompositeSubscription;

    protected void addSubscription(Subscription subscription) {
        if (null == mCompositeSubscription) {
            mCompositeSubscription = new CompositeSubscription();
        }
        mCompositeSubscription.add(subscription);
    }

    @Override protected void onDestroy() {
        if (null != mCompositeSubscription) {
            mCompositeSubscription.unsubscribe();
        }
        super.onDestroy();
    }
    ...
}

//2.X
public class AppBaseActivity extends AppCompatActivity {
    ...
    private   CompositeDisposable mCompositeDisposable;

    protected void addDisposable(Disposable disposable) {
        if (null == mCompositeDisposable) {
            mCompositeDisposable = new CompositeDisposable();
        }
        mCompositeDisposable.add(disposable);
    }

    @Override protected void onDestroy() {
        if (null != mCompositeDisposable) {
            mCompositeDisposable.clear();
        }
        super.onDestroy();
    }
    ...
}