模拟多张图片并行上传业务，所有的都成功后，才允许点击保存

--------单线程-----
12-25 15:59:22.737 24988 25035 D SpringItemViewActivity: testRxjavaToList request RxCachedThreadScheduler-2 tokenfile://a
12-25 15:59:23.164   932   950 I ActivityManager: Displayed com.pitaya.findviewbyiddemo/.SpringItemViewActivity: +1s985ms
12-25 15:59:24.738 24988 25035 D SpringItemViewActivity: testRxjavaToList request RxCachedThreadScheduler-2 tokenfile://b
12-25 15:59:24.738 24988 24988 D SpringItemViewActivity: testRxjavaToList subscribe main request done:tokenfile://a
12-25 15:59:26.738 24988 25035 D SpringItemViewActivity: testRxjavaToList request RxCachedThreadScheduler-2 tokenfile://c
12-25 15:59:26.738 24988 24988 D SpringItemViewActivity: testRxjavaToList subscribe main request done:tokenfile://b
12-25 15:59:28.739 24988 24988 D SpringItemViewActivity: testRxjavaToList subscribe main request done:tokenfile://c

        Observable.just("token").flatMap(new Function<String, ObservableSource<String>>() {
            @Override
            public ObservableSource<String> apply(String token) throws Exception {
                return Observable.fromIterable(stringList).map(new Function<String, String>() {
                    @Override
                    public String apply(String s) throws Exception {
                        return token + s;
                    }
                }).observeOn(Schedulers.io()).map(new Function<String, String>() {
                    @Override
                    public String apply(String s) throws Exception {
                        Log.d(TAG, "testRxjavaToList request " + getCurrentName() + " " + s);
                        Thread.sleep(2000);
                        return "request done:" + s;
                    }
                });
            }
        }).subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Consumer<String>() {
                    @Override
                    public void accept(String s) throws Exception {
                        Log.d(TAG, "testRxjavaToList subscribe " + getCurrentName() + " " + s);
                    }
                });


-----支持流并行执行-----

12-25 16:02:05.474 25972 26018 D SpringItemViewActivity: testRxjavaToList request RxCachedThreadScheduler-2 tokenfile://a
12-25 16:02:05.477 25972 26019 D SpringItemViewActivity: testRxjavaToList request RxCachedThreadScheduler-3 tokenfile://b
12-25 16:02:05.485 25972 26020 D SpringItemViewActivity: testRxjavaToList request RxCachedThreadScheduler-4 tokenfile://c
12-25 16:02:05.893   932   950 I ActivityManager: Displayed com.pitaya.findviewbyiddemo/.SpringItemViewActivity: +1s972ms
12-25 16:02:07.475 25972 25972 D SpringItemViewActivity: testRxjavaToList subscribe main request done:tokenfile://a
12-25 16:02:07.478 25972 25972 D SpringItemViewActivity: testRxjavaToList subscribe main request done:tokenfile://b
12-25 16:02:07.490 25972 25972 D SpringItemViewActivity: testRxjavaToList subscribe main request done:tokenfile://c


        //支持多线程并行，并行的最小单元是一条流。如何识别存在多条流的唯一方式是看是否存在flatMap(),并且FlatMap前有多少条流，就是多少能产生多少天新流，每个流
        //通过设置observeOn(Schedulers.io()可以并发执行
        Observable.just("token").flatMap(new Function<String, ObservableSource<String>>() {
            @Override
            public ObservableSource<String> apply(String token) throws Exception {
                return Observable.fromIterable(stringList).map(new Function<String, String>() {
                    @Override
                    public String apply(String s) throws Exception {
                        return token + s;
                    }
                }).flatMap(new Function<String, ObservableSource<String>>() {
                    @Override
                    public ObservableSource<String> apply(String s) throws Exception {
                        return Observable.just(s).observeOn(Schedulers.io()).map(new Function<String, String>() {
                            @Override
                            public String apply(String s) throws Exception {
                                Log.d(TAG, "testRxjavaToList request " + getCurrentName() + " " + s);
                                Thread.sleep(2000);
                                return "request done:" + s;
                            }
                        });
                    }
                });
            }
        }).subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Consumer<String>() {
                    @Override
                    public void accept(String s) throws Exception {
                        Log.d(TAG, "testRxjavaToList subscribe " + getCurrentName() + " " + s);
                    }
                });



-----------代码 支持线程并发、支持每个流更新UI、支持最后合并toList给UI一个最终结果、支持流过程异常降级处理-------

12-25 15:56:55.965   932  1661 I ActivityManager: Start proc 23904:com.pitaya.findviewbyiddemo/u0a71 for activity com.pitaya.findviewbyiddemo/.SpringItemViewActivity
12-25 15:56:57.519 23904 23949 D SpringItemViewActivity: testRxjavaToList merge token RxCachedThreadScheduler-1
12-25 15:56:57.521 23904 23949 D SpringItemViewActivity: testRxjavaToList merge token RxCachedThreadScheduler-1
12-25 15:56:57.522 23904 23951 D SpringItemViewActivity: testRxjavaToList request RxCachedThreadScheduler-2 tokenfile://a
12-25 15:56:57.523 23904 23949 D SpringItemViewActivity: testRxjavaToList merge token RxCachedThreadScheduler-1
12-25 15:56:57.526 23904 23952 D SpringItemViewActivity: testRxjavaToList request RxCachedThreadScheduler-3 tokenfile://b
12-25 15:56:57.526 23904 23953 D SpringItemViewActivity: testRxjavaToList request RxCachedThreadScheduler-4 tokenfile://c
12-25 15:56:57.956   932   950 I ActivityManager: Displayed com.pitaya.findviewbyiddemo/.SpringItemViewActivity: +2s27ms
12-25 15:56:59.523 23904 23904 D SpringItemViewActivity: testRxjavaToList apply map main request done:tokenfile://a
12-25 15:56:59.530 23904 23904 D SpringItemViewActivity: testRxjavaToList apply map main request done:tokenfile://c
12-25 15:56:59.536 23904 23904 D SpringItemViewActivity: testRxjavaToList apply map main  null 
12-25 15:56:59.548 23904 23904 D SpringItemViewActivity: testRxjavaToList subscribe main [request done:tokenfile://a, request done:tokenfile://c,  null ]


        //线程切换、异常处理onErrorReturnItem 的最小执行单位都是，而不是流内部含有for循环的操作符，比如Just、From等。

        ArrayList<String> stringList = new ArrayList<>();
        stringList.add("file://a");
        stringList.add("file://b");
        stringList.add("file://c");

        Observable.just("token").flatMap(new Function<String, ObservableSource<String>>() {
            @Override
            public ObservableSource<String> apply(String token) throws Exception {
                return Observable.fromIterable(stringList).map(new Function<String, String>() {
                    @Override
                    public String apply(String s) throws Exception {
                        Log.d(TAG, "testRxjavaToList merge token " + getCurrentName());
                        return token + s;
                    }
                }).flatMap(new Function<String, ObservableSource<String>>() {
                    @Override
                    public ObservableSource<String> apply(String s) throws Exception {
                        return Observable.just(s).observeOn(Schedulers.io()).map(new Function<String, String>() {
                            @Override
                            public String apply(String s) throws Exception {
                                Log.d(TAG, "testRxjavaToList request " + getCurrentName() + " " + s);
                                Thread.sleep(2000);
                                if (s.contains("file://b")) {
                                    throw new NullPointerException("服务器异常");  //服务器异常
                                }
                                return "request done:" + s;
                            }
                        }).onErrorReturnItem(" null "); //当前流出错后，降级处理
                    }
                }).observeOn(AndroidSchedulers.mainThread()).map(new Function<String, String>() {
                    @Override
                    public String apply(String s) throws Exception {
                        Log.d(TAG, "testRxjavaToList apply map " + getCurrentName() + " " + s);
                        Toast.makeText(getApplicationContext(), s, LENGTH_SHORT).show();//更新图标状态
                        return s;
                    }
                }).observeOn(Schedulers.io());
            }
        }).toList().toObservable().subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread()).subscribe(new Consumer<List<String>>() {
            @Override
            public void accept(List<String> strings) throws Exception {
                Log.d(TAG, "testRxjavaToList subscribe " + getCurrentName() + " " + strings);
            }
        });