知识树杂谈(2)

一、RxJava理论学习

     a. 参考文章

       http://gank.io/post/560e15be2dca930e00da1083#toc_28

        http://gank.io/post/560e15be2dca930e00da1083

     b. 含义

         a library for composing asynchronous and event-based programs by using observable sequences. 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。  

        特性：   扩展的观察者模式、异步(线程控制)、变换(类型转换)。

     c. 简单例子

         通过一个url加载一张图，恩为了演示RxJava和线程控制，我用HttpUrlConnection来做一个实例。

         

Observable.create(new Observable.OnSubscribe<Bitmap>() {
            @Override
            public void call(Subscriber<? super Bitmap> subscriber) {
                try {
                    URL url = new URL("http://img4.imgtn.bdimg.com/it/u=815679381,647288773&fm=21&gp=0.jpg");
                    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                    connection.setRequestMethod("GET");
                    connection.setConnectTimeout(8000);
                    connection.setReadTimeout(8000);

                    InputStream in = connection.getInputStream();
                    Bitmap bitmap = BitmapFactory.decodeStream(in);
                    subscriber.onNext(bitmap);
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        })
                .observeOn(AndroidSchedulers.mainThread())  //指定subscriber的回调发生在UI线程
                .subscribeOn(Schedulers.newThread())        //指定subscribe()发生在新线程
                .subscribe(new Subscriber<Bitmap>() {
                    @Override
                    public void onCompleted() {
                        plan.setVisibility(View.GONE);
                    }

                    @Override
                    public void onError(Throwable e) {
                        e.printStackTrace();
                    }

                    @Override
                    public void onNext(Bitmap bitmap) {
                        if (bitmap != null) {
                            image.setImageBitmap(bitmap);
                            onCompleted();
                        }
                    }
                });
    }