android使用RxJava实现预加载

import android.support.annotation.NonNull;import java.util.LinkedList;import rx.Observable;import rx.Observer;import rx.Subscriber;import rx.Subscription;import rx.android.schedulers.AndroidSchedulers;import rx.functions.Action1;import rx.schedulers.Schedulers;import rx.subjects.BehaviorSubject;/** * 预加载 * preLoader = RxPreLoader.preLoad(observable); * preLoader.get(observer1); * preLoader.get(observer2); * preLoader.reload(); * preLoader.destroy() * * @author billy.qi */public class RxPreLoader<T> { private BehaviorSubject<T> subject; private Observable<T> observable; private Subscription subscription; private final LinkedList<Subscription> allObserver = new LinkedList<>(); private RxPreLoader(Observable<T> observable) { //注意的是由于onCompleted也是数据流中的一个 //如果直接observer.subscribeOn(Schedulers.io()).subscribe(subject); //会导致subject只能缓存onCompleted //所以此处新建一个OnSubscribe，通过调用subject.onNext(t)的方式来缓存数据 this.observable = observable; subject = BehaviorSubject.create(); subscription = Observable.create(new Observable.OnSubscribe<T>() {  @Override  public void call(Subscriber<? super T> subscriber) {  performLoad();  } }) .subscribeOn(Schedulers.io()) .subscribe(subject); } public static <R> RxPreLoader<R> preLoad(@NonNull Observable<R> observable) { return new RxPreLoader<R>(observable); } public void reload() { performLoad(); } public Subscription get(Observer<T> observer) { Subscription subscription = subject.observeOn(AndroidSchedulers.mainThread())  .subscribe(observer); allObserver.add(subscription); return subscription; } private void performLoad() { observable.subscribeOn(Schedulers.io())  .subscribe(new Action1<T>() {   @Override   public void call(T t) {   if (subject != null) {    subject.onNext(t);   }   }  }, new Action1<Throwable>() {   @Override   public void call(Throwable throwable) {   throwable.printStackTrace();   }  }); } public void destroy() { synchronized (allObserver) {  while(!allObserver.isEmpty()) {  unsubscribe(allObserver.removeFirst());  } } unsubscribe(subscription); subscription = null; subject = null; } private void unsubscribe(Subscription subscription) { if (subscription != null && !subscription.isUnsubscribed()) {  subscription.unsubscribe(); } }}

import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.widget.TextView;import java.util.concurrent.TimeUnit;import rx.Observable;import rx.Subscriber;/** * 使用RxJava实现的预加载方式 */public class RxPreLoaderActivity extends AppCompatActivity { private TextView textView; private RxPreLoader<String> preLoader; @Override protected void onCreate(Bundle savedInstanceState) { preLoad();//启动预加载 initLayout(savedInstanceState); preLoader.get(observer);//展示预加载的数据 } //初始化布局 private void initLayout(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); setTitle("使用RxPreLoader"); //通过循环多次findById来模拟复杂页面布局初始化的耗时 textView = (TextView)findViewById(R.id.textView); } //展示预加载的数据 Subscriber<String> observer = new Subscriber<String>() { @Override public void onCompleted() { } @Override public void onError(Throwable e) {  e.printStackTrace(); } @Override public void onNext(String s) {  textView.setText(s); } }; private void preLoad() { preLoader = RxPreLoader.preLoad(Observable.just("result").delay(500, TimeUnit.MILLISECONDS)); } @Override protected void onDestroy() { super.onDestroy(); preLoader.destroy();//销毁 }}