RxJava响应式编程之初级了解

时间 2019-11-11

标签 rxjava 响应编程初级了解栏目 Java 繁體版

原文原文链接

听说如今流行的开发模式是 Retrofit+RxJava+MVP+ButterKnifephp

若是想要简单学习ButterKnife、MVP模式，能够参考我之前的例子
使用butterknife注解框架
 Android—MVP设计模式高级（三）java

今天我就简单来学习下RxJava的相关知识
之前我也只是据说过RxJava，RxJava这个究竟是什么东西呢？
呵呵，它实际上是一个库，因此咱们使用里面的方法，得须要下载库，因此咱们须要在AS中进行配置react

1.RxJava 地址以及添加android

github地址：
https://github.com/ReactiveX/RxJava
或者
https://github.com/ReactiveX/RxAndroidgit

依赖库添加：
compile ‘io.reactivex:rxjava:1.1.6’
或者
compile ‘io.reactivex:rxandroid:1.2.1’github

2.RxJava是什么类型的库？它的原理是什么？数据库

RxJava 在 GitHub 主页上的自我介绍是 “a library for composing asynchronous and event-based programs using observable sequences for the Java VM”（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）。这就是 RxJava ，归纳得很是精准。编程

Rx：函数响应式编程，也许这个词对你我都很只可意会，不可言传，先抛开Rx不说，咱们接触到的相似的这样的思路，大概有接口回调、Handler通信、广播通信、还有一个开源的EventBus、以及ContentPorivider里面的观察者模式、AsyncTask 咱们朦胧中也许就大概了解RxJava是怎么个东西了。设计模式

RxJava 的异步实现，是经过一种扩展的观察者模式来实现的。
至于观察者我就拿ContentProvider来讲吧，好比咱们在一个ContentProvider中有一个insert方法，插入完毕后，去通知某个监听该URI变化的界面api

<code class="hljs avrasm has-numbering">getContext()<span class="hljs-preprocessor">.getContentResolver</span>()<span class="hljs-preprocessor">.notifyChange</span>(URI, null)<span class="hljs-comment">;</span></code><ul style="" class="pre-numbering"><li>1</li></ul><ul style="" class="pre-numbering"><li>1</li></ul>

好比在MainActivity中去registerContentObserver注册一个内容观察者

<code class="hljs java has-numbering"><span class="hljs-keyword">private</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">final</span> Uri URI = Uri  
            .parse(<span class="hljs-string">"content://com.example.contentprovider.MyContentProvider/student"</span>);  
 contentResolver.registerContentObserver(uri, <span class="hljs-keyword">true</span>, observer);</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li></ul>

<code class="hljs java has-numbering"> <span class="hljs-keyword">private</span> ContentObserver observer = <span class="hljs-keyword">new</span> ContentObserver(<span class="hljs-keyword">null</span>) {  
        <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onChange</span>(<span class="hljs-keyword">boolean</span> selfChange) {  
            <span class="hljs-comment">// 说明数据有改变,从新查询一直全部记录  </span>
            Uri uri = Uri.parse(<span class="hljs-string">"content://com.example.contentprovider.MyContentProvider/student"</span>);  
            Cursor cursor = contentResolver.query(uri, <span class="hljs-keyword">null</span>, <span class="hljs-keyword">null</span>, <span class="hljs-keyword">null</span>, <span class="hljs-keyword">null</span>);  
            Log.e(<span class="hljs-string">"TAG"</span>, <span class="hljs-string">"onChange()  count="</span> + cursor.getCount());  
        };  
    };  </code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li></ul>

那么对于RxJava 的观察者模式呢？
RxJava 有四个基本概念：Observable (被观察者)、 Observer (观察者)、 subscribe (订阅)、事件。
对比ContentProvider，RxJava里面的被观察者就是某个Uri(也就是某个数据库)，观察者就是某个界面（好比MainActivity）,订阅就是registerContentObserver，事件就是insert方法

Rxjava本质主要就是异步任务外层构建了一个观察者的设计模式它更简洁咱们调用api方法几乎看不到方法里面的分线程数据操做它只是利用了一种观察者的设计模式来进行主分线程的通信来进行响应操做

咱们来看看RxJava的察者模式流程交互图：

与传统观察者模式不一样， RxJava 的事件回调方法除了普通事件 onNext() （至关于 insert）以外，还定义了两个特殊的事件：onCompleted() 和 onError()。

咱们来看下Observable是如何定义的？

<code class="hljs avrasm has-numbering">     Observable<span class="hljs-preprocessor">.create</span>(new Observable<span class="hljs-preprocessor">.OnSubscribe</span><String>() {
            @Override
            public void <span class="hljs-keyword">call</span>(Subscriber<? super String> subscriber) {
                Log<span class="hljs-preprocessor">.d</span>(TAG, <span class="hljs-string">"call: threadId:"</span> + Thread<span class="hljs-preprocessor">.currentThread</span>()<span class="hljs-preprocessor">.getId</span>())<span class="hljs-comment">;</span>
                subscriber<span class="hljs-preprocessor">.onStart</span>()<span class="hljs-comment">;</span>
                subscriber<span class="hljs-preprocessor">.onNext</span>(<span class="hljs-string">"Hello World!"</span>)<span class="hljs-comment">;</span>
                subscriber<span class="hljs-preprocessor">.onCompleted</span>()<span class="hljs-comment">;</span>
            }
        })</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li></ul>

咱们看看create源码里面作了什么？

<code class="hljs cs has-numbering">   <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <T> Observable<T> <span class="hljs-title">create</span>(OnSubscribe<T> f) {
        <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> Observable<T>(hook.onCreate(f));
    }</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li></ul>

能够看到，这里传入了一个 OnSubscribe 对象做为参数。OnSubscribe 会被存储在返回的 Observable 对象中，当 Observable 被订阅的时候，OnSubscribe 的 call() 方法会自动被调用，事件序列就会依照设定依次触发（对于上面的代码，就是观察者Subscriber 将会被调用一次 onNext() 和一次 onCompleted()）。这样，由被观察者调用了观察者的回调方法，就实现了由被观察者向观察者的事件传递，即观察者模式。

而后在看Observer中作了什么操做？

<code class="hljs lasso has-numbering">subscribe(<span class="hljs-literal">new</span> Observer<span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span>() {
                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> onCompleted() {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>d(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"onCompleted: threadId:"</span> <span class="hljs-subst">+</span> <span class="hljs-keyword">Thread</span><span class="hljs-built_in">.</span>currentThread()<span class="hljs-built_in">.</span>getId());
                    }

                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> onError(Throwable e) {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>e(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"onError: threadId:"</span> <span class="hljs-subst">+</span> <span class="hljs-keyword">Thread</span><span class="hljs-built_in">.</span>currentThread()<span class="hljs-built_in">.</span>getId());
                    }

                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> onNext(<span class="hljs-built_in">String</span> s) {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>d(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"onNext: threadId:"</span> <span class="hljs-subst">+</span> <span class="hljs-keyword">Thread</span><span class="hljs-built_in">.</span>currentThread()<span class="hljs-built_in">.</span>getId());
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>i(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"onNext: s = "</span> <span class="hljs-subst">+</span> s);
                    }
                });</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li></ul>

onCompleted(): 事件队列完结。RxJava 不只把每一个事件单独处理，还会把它们看作一个队列。RxJava 规定，当不会再有新的 onNext() 发出时，须要触发 onCompleted() 方法做为标志。
onError(): 事件队列异常。在事件处理过程当中出异常时，onError() 会被触发，同时队列自动终止，不容许再有事件发出。
在一个正确运行的事件序列中, onCompleted() 和 onError() 有且只有一个，而且是事件序列中的最后一个。须要注意的是，onCompleted() 和 onError() 两者也是互斥的，即在队列中调用了其中一个，就不该该再调用另外一个。

接下来咱们将所有的代码贴出来，看看Log日志打印：

同步方式

<code class="hljs java has-numbering"><span class="hljs-keyword">package</span> com.example.administrator.myapplication;
<span class="hljs-keyword">import</span> android.app.Activity;
<span class="hljs-keyword">import</span> android.os.Bundle;
<span class="hljs-keyword">import</span> android.util.Log;

<span class="hljs-keyword">import</span> rx.Observable;
<span class="hljs-keyword">import</span> rx.Observer;
<span class="hljs-keyword">import</span> rx.Subscriber;

<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">MainActivity</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Activity</span> {</span>
    <span class="hljs-keyword">private</span> String TAG = <span class="hljs-string">"MainActivity"</span>;
    <span class="hljs-annotation">@Override</span>
    <span class="hljs-keyword">protected</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onCreate</span>(Bundle savedInstanceState) {
        <span class="hljs-keyword">super</span>.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Observable.create(<span class="hljs-keyword">new</span> Observable.OnSubscribe<String>() {
            <span class="hljs-annotation">@Override</span>
            <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">call</span>(Subscriber<? <span class="hljs-keyword">super</span> String> subscriber) {
                Log.d(TAG, <span class="hljs-string">"call: threadId:"</span> + Thread.currentThread().getId());
                subscriber.onStart();
                subscriber.onNext(<span class="hljs-string">"Hello World!"</span>);
                subscriber.onCompleted();
            }
        })
                .subscribe(<span class="hljs-keyword">new</span> Observer<String>() {
                    <span class="hljs-annotation">@Override</span>
                    <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onCompleted</span>() {
                        Log.d(TAG, <span class="hljs-string">"onCompleted: threadId:"</span> + Thread.currentThread().getId());
                    }

                    <span class="hljs-annotation">@Override</span>
                    <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onError</span>(Throwable e) {
                        Log.e(TAG, <span class="hljs-string">"onError: threadId:"</span> + Thread.currentThread().getId());
                    }

                    <span class="hljs-annotation">@Override</span>
                    <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onNext</span>(String s) {
                        Log.d(TAG, <span class="hljs-string">"onNext: threadId:"</span> + Thread.currentThread().getId());
                        Log.i(TAG, <span class="hljs-string">"onNext: s = "</span> + s);
                    }
                });
    }
}
</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li><li>21</li><li>22</li><li>23</li><li>24</li><li>25</li><li>26</li><li>27</li><li>28</li><li>29</li><li>30</li><li>31</li><li>32</li><li>33</li><li>34</li><li>35</li><li>36</li><li>37</li><li>38</li><li>39</li><li>40</li><li>41</li><li>42</li><li>43</li><li>44</li><li>45</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li><li>21</li><li>22</li><li>23</li><li>24</li><li>25</li><li>26</li><li>27</li><li>28</li><li>29</li><li>30</li><li>31</li><li>32</li><li>33</li><li>34</li><li>35</li><li>36</li><li>37</li><li>38</li><li>39</li><li>40</li><li>41</li><li>42</li><li>43</li><li>44</li><li>45</li></ul>

<code class="hljs http has-numbering"><span class="hljs-attribute">call</span>: <span class="hljs-string">threadId:1</span>
<span class="hljs-attribute">onNext</span>: <span class="hljs-string">threadId:1</span>
<span class="hljs-attribute">onNext</span>: <span class="hljs-string">s = Hello World!</span>
<span class="hljs-attribute">onCompleted</span>: <span class="hljs-string">threadId:1</span></code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li></ul>

从上能够看出，事件的处理和结果的接收都是在同一个线程里面处理的。可是，Rxjava的意义何在，异步呢？别急，看如下代码的处理，你就会发现了，异步原来是这么的简单。
异步方式
咱们将上面的代码稍微改下，增长2行代码

<code class="hljs lasso has-numbering">        Observable<span class="hljs-built_in">.</span>create(<span class="hljs-literal">new</span> Observable<span class="hljs-built_in">.</span>OnSubscribe<span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span>() {
            @Override
            <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> call(Subscriber<span class="hljs-subst"><?</span> super <span class="hljs-built_in">String</span><span class="hljs-subst">></span> subscriber) {
                <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>d(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"call: threadId:"</span> <span class="hljs-subst">+</span> <span class="hljs-keyword">Thread</span><span class="hljs-built_in">.</span>currentThread()<span class="hljs-built_in">.</span>getId());
                subscriber<span class="hljs-built_in">.</span>onStart();
                subscriber<span class="hljs-built_in">.</span>onNext(<span class="hljs-string">"Hello World!"</span>);
                subscriber<span class="hljs-built_in">.</span>onCompleted();
            }
        })
                <span class="hljs-built_in">.</span>subscribeOn(Schedulers<span class="hljs-built_in">.</span>io())
                <span class="hljs-built_in">.</span>observeOn(AndroidSchedulers<span class="hljs-built_in">.</span>mainThread())
                <span class="hljs-built_in">.</span>subscribe(<span class="hljs-literal">new</span> Observer<span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span>() {
                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> onCompleted() {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>d(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"onCompleted: threadId:"</span> <span class="hljs-subst">+</span> <span class="hljs-keyword">Thread</span><span class="hljs-built_in">.</span>currentThread()<span class="hljs-built_in">.</span>getId());
                    }

                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> onError(Throwable e) {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>e(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"onError: threadId:"</span> <span class="hljs-subst">+</span> <span class="hljs-keyword">Thread</span><span class="hljs-built_in">.</span>currentThread()<span class="hljs-built_in">.</span>getId());
                    }

                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> onNext(<span class="hljs-built_in">String</span> s) {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>d(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"onNext: threadId:"</span> <span class="hljs-subst">+</span> <span class="hljs-keyword">Thread</span><span class="hljs-built_in">.</span>currentThread()<span class="hljs-built_in">.</span>getId());
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>i(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"onNext: s = "</span> <span class="hljs-subst">+</span> s);
                    }
                });</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li><li>21</li><li>22</li><li>23</li><li>24</li><li>25</li><li>26</li><li>27</li><li>28</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li><li>21</li><li>22</li><li>23</li><li>24</li><li>25</li><li>26</li><li>27</li><li>28</li></ul>

咱们添上以下2行代码

<code class="hljs avrasm has-numbering"><span class="hljs-preprocessor">.subscribeOn</span>(Schedulers<span class="hljs-preprocessor">.io</span>())
<span class="hljs-preprocessor">.observeOn</span>(AndroidSchedulers<span class="hljs-preprocessor">.mainThread</span>())</code><ul style="" class="pre-numbering"><li>1</li><li>2</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li></ul>

咱们看下Log输出

<code class="hljs mathematica has-numbering"><span class="hljs-number">03</span>-<span class="hljs-number">08</span> <span class="hljs-number">07</span>:<span class="hljs-number">20</span>:<span class="hljs-number">18.101</span> <span class="hljs-number">22734</span>-<span class="hljs-number">22734</span>/? <span class="hljs-keyword">I</span>/MainActivity: testFunction: threadId:<span class="hljs-number">1</span>
<span class="hljs-number">03</span>-<span class="hljs-number">08</span> <span class="hljs-number">07</span>:<span class="hljs-number">20</span>:<span class="hljs-number">18.123</span> <span class="hljs-number">22734</span>-<span class="hljs-number">22755</span>/? <span class="hljs-keyword">D</span>/MainActivity: call: threadId:<span class="hljs-number">180</span>
<span class="hljs-number">03</span>-<span class="hljs-number">08</span> <span class="hljs-number">07</span>:<span class="hljs-number">20</span>:<span class="hljs-number">18.142</span> <span class="hljs-number">22734</span>-<span class="hljs-number">22734</span>/? <span class="hljs-keyword">D</span>/MainActivity: onNext: threadId:<span class="hljs-number">1</span>
<span class="hljs-number">03</span>-<span class="hljs-number">08</span> <span class="hljs-number">07</span>:<span class="hljs-number">20</span>:<span class="hljs-number">18.142</span> <span class="hljs-number">22734</span>-<span class="hljs-number">22734</span>/? <span class="hljs-keyword">I</span>/MainActivity: onNext: s = Hello World!
<span class="hljs-number">03</span>-<span class="hljs-number">08</span> <span class="hljs-number">07</span>:<span class="hljs-number">20</span>:<span class="hljs-number">18.143</span> <span class="hljs-number">22734</span>-<span class="hljs-number">22734</span>/? <span class="hljs-keyword">D</span>/MainActivity: onCompleted: threadId:<span class="hljs-number">1</span></code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li></ul>

看见了没，第二行log日志threadId与其它的threadId很明显的不同啊，说明咱们在处理事件的时候，发生在了一个新的线程里面，而结果的接收，仍是在主线程里面操做的。怎么样，只要添加两句话，异步立马就实现了，异步处理耗时操做，就是这么easy。

咱们简单看下源码

<code class="hljs java has-numbering"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">final</span> Observable<T> <span class="hljs-title">subscribeOn</span>(Scheduler scheduler) {
        <span class="hljs-keyword">if</span> (<span class="hljs-keyword">this</span> <span class="hljs-keyword">instanceof</span> ScalarSynchronousObservable) {
            <span class="hljs-keyword">return</span> ((ScalarSynchronousObservable<T>)<span class="hljs-keyword">this</span>).scalarScheduleOn(scheduler);
        }
        <span class="hljs-keyword">return</span> create(<span class="hljs-keyword">new</span> OperatorSubscribeOn<T>(<span class="hljs-keyword">this</span>, scheduler));
    }</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li></ul>

什么意思呢？
Scheduler scheduler参数就是执行订阅操做，返回一个源观察到的修改，使其订阅发生在指定的线程
observeOn(AndroidSchedulers.mainThread())
句话说，observeOn() 指定的是它以后的操做所在的线程。

打印字符串数组 from和just方式

以上是RxJava的很基础很简单的一个用法，那么咱们接着往下看，好比咱们有一组需求把一个String数组的字符串，单个打印出来，咱们用Rxjava怎么实现呢？看代码：

<code class="hljs java has-numbering">Log.i(TAG, <span class="hljs-string">"testFunction: threadId:"</span> + Thread.currentThread().getId());
        Observable.from(<span class="hljs-keyword">new</span> String[]{<span class="hljs-string">"one"</span>,<span class="hljs-string">"two"</span>,<span class="hljs-string">"three"</span>,<span class="hljs-string">"four"</span>})
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(<span class="hljs-keyword">new</span> Observer<String>() {
                    <span class="hljs-annotation">@Override</span>
                    <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onCompleted</span>() {
                        Log.d(TAG, <span class="hljs-string">"onCompleted: threadId:"</span> + Thread.currentThread().getId());
                    }

                    <span class="hljs-annotation">@Override</span>
                    <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onError</span>(Throwable e) {
                        Log.e(TAG, <span class="hljs-string">"onError: threadId:"</span> + Thread.currentThread().getId());
                    }

                    <span class="hljs-annotation">@Override</span>
                    <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onNext</span>(String s) {
                        Log.i(TAG, <span class="hljs-string">"onNext: s = "</span> + s);
                    }
                });</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li></ul>

看Log输出日志以下：

<code class="hljs http has-numbering"><span class="hljs-attribute">testFunction</span>: <span class="hljs-string">threadId:1</span>
<span class="hljs-attribute">onNext</span>: <span class="hljs-string">s = one</span>
<span class="hljs-attribute">onNext</span>: <span class="hljs-string">s = two</span>
<span class="hljs-attribute">onNext</span>: <span class="hljs-string">s = three</span>
<span class="hljs-attribute">onNext</span>: <span class="hljs-string">s = four</span>
<span class="hljs-attribute">onCompleted</span>: <span class="hljs-string">threadId:1</span>
</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li></ul>

From操做符用来将某个对象转化为Observable对象，而且依次将其内容发射出去。这个相似于just，可是just会将这个对象整个发射出去。好比说一个含有3个字符串的数组，使用from就会发射4次，每次发射一个数字，而使用just会发射一次来将整个的数组发射出去。

<code class="hljs lasso has-numbering"> <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>i(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"testFunction: threadId:"</span><span class="hljs-subst">+</span><span class="hljs-keyword">Thread</span><span class="hljs-built_in">.</span>currentThread()<span class="hljs-built_in">.</span>getId());
        Observable<span class="hljs-built_in">.</span>just(<span class="hljs-string">"one"</span>, <span class="hljs-string">"two"</span>, <span class="hljs-string">"three"</span>, <span class="hljs-string">"four"</span>)
                <span class="hljs-built_in">.</span>subscribeOn(Schedulers<span class="hljs-built_in">.</span>io())
                <span class="hljs-built_in">.</span>observeOn(AndroidSchedulers<span class="hljs-built_in">.</span>mainThread())
                <span class="hljs-built_in">.</span>subscribe(<span class="hljs-literal">new</span> Observer<span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span>() {
                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> onCompleted() {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>d(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"onCompleted: threadId:"</span> <span class="hljs-subst">+</span> <span class="hljs-keyword">Thread</span><span class="hljs-built_in">.</span>currentThread()<span class="hljs-built_in">.</span>getId());
                    }

                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> onError(Throwable e) {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>e(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"onError: threadId:"</span> <span class="hljs-subst">+</span> <span class="hljs-keyword">Thread</span><span class="hljs-built_in">.</span>currentThread()<span class="hljs-built_in">.</span>getId());
                    }

                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> onNext(<span class="hljs-built_in">String</span> s) {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>i(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"onNext: s = "</span> <span class="hljs-subst">+</span> s);
                    }
                });</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li></ul>

<code class="hljs mathematica has-numbering"><span class="hljs-number">03</span>-<span class="hljs-number">08</span> <span class="hljs-number">08</span>:<span class="hljs-number">09</span>:<span class="hljs-number">25.743</span> <span class="hljs-number">32155</span>-<span class="hljs-number">32155</span>/? <span class="hljs-keyword">I</span>/MainActivity: testFunction: threadId:<span class="hljs-number">1</span>
<span class="hljs-number">03</span>-<span class="hljs-number">08</span> <span class="hljs-number">08</span>:<span class="hljs-number">09</span>:<span class="hljs-number">25.784</span> <span class="hljs-number">32155</span>-<span class="hljs-number">32155</span>/? <span class="hljs-keyword">I</span>/MainActivity: onNext: s = one
<span class="hljs-number">03</span>-<span class="hljs-number">08</span> <span class="hljs-number">08</span>:<span class="hljs-number">09</span>:<span class="hljs-number">25.785</span> <span class="hljs-number">32155</span>-<span class="hljs-number">32155</span>/? <span class="hljs-keyword">I</span>/MainActivity: onNext: s = two
<span class="hljs-number">03</span>-<span class="hljs-number">08</span> <span class="hljs-number">08</span>:<span class="hljs-number">09</span>:<span class="hljs-number">25.785</span> <span class="hljs-number">32155</span>-<span class="hljs-number">32155</span>/? <span class="hljs-keyword">I</span>/MainActivity: onNext: s = three
<span class="hljs-number">03</span>-<span class="hljs-number">08</span> <span class="hljs-number">08</span>:<span class="hljs-number">09</span>:<span class="hljs-number">25.785</span> <span class="hljs-number">32155</span>-<span class="hljs-number">32155</span>/? <span class="hljs-keyword">I</span>/MainActivity: onNext: s = four
<span class="hljs-number">03</span>-<span class="hljs-number">08</span> <span class="hljs-number">08</span>:<span class="hljs-number">09</span>:<span class="hljs-number">25.785</span> <span class="hljs-number">32155</span>-<span class="hljs-number">32155</span>/? <span class="hljs-keyword">D</span>/MainActivity: onCompleted: threadId:<span class="hljs-number">1</span>
</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li></ul>

一对一转换

<code class="hljs lasso has-numbering"> <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>i(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"testFunction: threadId:"</span><span class="hljs-subst">+</span><span class="hljs-keyword">Thread</span><span class="hljs-built_in">.</span>currentThread()<span class="hljs-built_in">.</span>getId());
        Observable<span class="hljs-built_in">.</span>just(<span class="hljs-string">"1"</span>, <span class="hljs-string">"2"</span>, <span class="hljs-string">"3"</span>, <span class="hljs-string">"4"</span>)
                <span class="hljs-built_in">.</span>subscribeOn(Schedulers<span class="hljs-built_in">.</span>io())
                <span class="hljs-built_in">.</span>observeOn(AndroidSchedulers<span class="hljs-built_in">.</span>mainThread())
                <span class="hljs-built_in">.</span><span class="hljs-built_in">map</span>(<span class="hljs-literal">new</span> Func1<span class="hljs-subst"><</span><span class="hljs-built_in">String</span>, <span class="hljs-built_in">Integer</span><span class="hljs-subst">></span>() {

                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-built_in">Integer</span> call(<span class="hljs-built_in">String</span> s) {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>i(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"call: s = "</span><span class="hljs-subst">+</span>s);
                        <span class="hljs-keyword">return</span> <span class="hljs-built_in">Integer</span><span class="hljs-built_in">.</span>parseInt(s);
                    }
                })
                <span class="hljs-built_in">.</span>subscribe(<span class="hljs-literal">new</span> Action1<span class="hljs-subst"><</span><span class="hljs-built_in">Integer</span><span class="hljs-subst">></span>() {
                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> call(<span class="hljs-built_in">Integer</span> <span class="hljs-built_in">integer</span>) {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>i(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"call: integer = "</span><span class="hljs-subst">+</span><span class="hljs-built_in">integer</span>);
                    }
                });</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li></ul>

<code class="hljs http has-numbering"><span class="hljs-attribute">testFunction</span>: <span class="hljs-string">threadId:1</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">s = 1</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">integer = 1</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">s = 2</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">integer = 2</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">s = 3</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">integer = 3</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">s = 4</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">integer = 4</span></code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li></ul>

简单说一下Func1，其中的T表示传入的参数类型，R表示方法返回的参数类型。源码以下：

<code class="hljs php has-numbering"><span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">interface</span> <span class="hljs-title">Func1</span><<span class="hljs-title">T</span>, <span class="hljs-title">R</span>> <span class="hljs-keyword">extends</span> <span class="hljs-title">Function</span> {</span>
    R call(T t);
}
</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li></ul>

上例中还有一个叫作 Action1的类。也是 RxJava 的一个接口，用于包装含有无参数的方法。 Func1 和 Action 的区别在于， Func1 包装的是有返回值的方法。另外，和 ActionX 同样， FuncX 也有多个，用于不一样参数个数的方法。FuncX 和 ActionX 的区别在 FuncX 包装的是有返回值的方法。

能够看到，map() 方法将参数中的 String 对象转换成一个 Integer对象后返回，而在通过 map() 方法后，事件的参数类型也由 String 转为了 Integer。这种直接变换对象并返回的，是最多见的也最容易理解的变换。不过 RxJava 的变换远不止这样，它不只能够针对事件对象，还能够针对整个事件队列，这使得 RxJava 变得很是灵活。

封装Observable一对多转换
map转换，是一对一的转换，像示例当中，咱们把string转成int，可是当咱们须要一对多的转换，该怎么作呢？好比说，定义一个学生类：

<code class="hljs cs has-numbering">package com.example.administrator.myapplication;

import java.util.List;

<span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> Student {

    <span class="hljs-keyword">private</span> String name;

    <span class="hljs-keyword">public</span> String <span class="hljs-title">getName</span>() {
        <span class="hljs-keyword">return</span> name;
    }

    <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setName</span>(String name) {
        <span class="hljs-keyword">this</span>.name = name;
    }

    <span class="hljs-comment"><span class="hljs-xmlDocTag">///</span><span class="hljs-xmlDocTag">///</span><span class="hljs-xmlDocTag">///</span><span class="hljs-xmlDocTag">///</span><span class="hljs-xmlDocTag">///</span><span class="hljs-xmlDocTag">///</span><span class="hljs-xmlDocTag">///</span><span class="hljs-xmlDocTag">///</span>//</span>
    <span class="hljs-keyword">private</span> List<String> courses;


    <span class="hljs-keyword">public</span> List<String> <span class="hljs-title">getCourses</span>() {
        <span class="hljs-keyword">return</span> courses;
    }

    <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setCourses</span>(List<String> courses) {
        <span class="hljs-keyword">this</span>.courses = courses;
    }
}</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li><li>21</li><li>22</li><li>23</li><li>24</li><li>25</li><li>26</li><li>27</li><li>28</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li><li>21</li><li>22</li><li>23</li><li>24</li><li>25</li><li>26</li><li>27</li><li>28</li></ul>

<code class="hljs lasso has-numbering">
        Student student1 <span class="hljs-subst">=</span> <span class="hljs-literal">new</span> Student();
        student1<span class="hljs-built_in">.</span>setName(<span class="hljs-string">"safly"</span>);
        <span class="hljs-built_in">List</span><span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span> courses <span class="hljs-subst">=</span> <span class="hljs-literal">new</span> ArrayList<span class="hljs-subst"><></span>();
        courses<span class="hljs-built_in">.</span>add(<span class="hljs-string">"语文"</span>);
        courses<span class="hljs-built_in">.</span>add(<span class="hljs-string">"数学"</span>);
        courses<span class="hljs-built_in">.</span>add(<span class="hljs-string">"英语"</span>);
        student1<span class="hljs-built_in">.</span>setCourses(courses);

        Student student2 <span class="hljs-subst">=</span> <span class="hljs-literal">new</span> Student();
        student2<span class="hljs-built_in">.</span>setName(<span class="hljs-string">"wyf"</span>);
        <span class="hljs-built_in">List</span><span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span> courses2 <span class="hljs-subst">=</span> <span class="hljs-literal">new</span> ArrayList<span class="hljs-subst"><></span>();
        courses2<span class="hljs-built_in">.</span>add(<span class="hljs-string">"化学"</span>);
        courses2<span class="hljs-built_in">.</span>add(<span class="hljs-string">"地理"</span>);
        courses2<span class="hljs-built_in">.</span>add(<span class="hljs-string">"政治"</span>);
        student2<span class="hljs-built_in">.</span>setCourses(courses2);



        Observable<span class="hljs-built_in">.</span>just(student1,student2)
                <span class="hljs-built_in">.</span>subscribe(<span class="hljs-literal">new</span> Action1<span class="hljs-subst"><</span>Student<span class="hljs-subst">></span>() {
                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> call(Student student) {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>i(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"call: name = "</span><span class="hljs-subst">+</span>student<span class="hljs-built_in">.</span>getName());
                        <span class="hljs-built_in">List</span><span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span> course <span class="hljs-subst">=</span> student<span class="hljs-built_in">.</span>getCourses();
                        for(<span class="hljs-built_in">String</span> str:course){
                            <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>i(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"call: str = "</span><span class="hljs-subst">+</span>str);
                        }
                    }
                });</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li><li>21</li><li>22</li><li>23</li><li>24</li><li>25</li><li>26</li><li>27</li><li>28</li><li>29</li><li>30</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li><li>21</li><li>22</li><li>23</li><li>24</li><li>25</li><li>26</li><li>27</li><li>28</li><li>29</li><li>30</li></ul>

这里咱们没有进行转换，直接just发送过来，没有用到转换，而后在call中进行直接输出了

<code class="hljs http has-numbering"><span class="hljs-attribute">call</span>: <span class="hljs-string">name = safly</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">str = 语文</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">str = 数学</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">str = 英语</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">name = wyf</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">str = 化学</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">str = 地理</span>
<span class="hljs-attribute">call</span>: <span class="hljs-string">str = 政治</span>
</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li></ul>

咱们用转换来试试看？
这里咱们用到了flatmap这一函数，按通俗的一点理解：咱们首先把Student转成了Observable，而后呢，又把student.getCourses()转成string挨个打印出来，结果以下：

<code class="hljs lasso has-numbering"> Observable<span class="hljs-built_in">.</span>just(student1,student2)
                  <span class="hljs-built_in">.</span>flatMap(<span class="hljs-literal">new</span> Func1<span class="hljs-subst"><</span>Student, Observable<span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">>></span>() {
                      @Override
                      <span class="hljs-keyword">public</span> Observable<span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span> call(Student student) {
                       <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>i(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"Observable "</span> );
                          <span class="hljs-keyword">return</span> Observable<span class="hljs-built_in">.</span>from(student<span class="hljs-built_in">.</span>getCourses());
                      }
                  })
                <span class="hljs-built_in">.</span>subscribe(<span class="hljs-literal">new</span> Action1<span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span>() {
                    @Override
                    <span class="hljs-keyword">public</span> <span class="hljs-literal">void</span> call(<span class="hljs-built_in">String</span> s) {
                        <span class="hljs-keyword">Log</span><span class="hljs-built_in">.</span>i(<span class="hljs-built_in">TAG</span>, <span class="hljs-string">"call: s = "</span><span class="hljs-subst">+</span>s);     
                    }
                });</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li></ul>

输出

<code class="hljs vbnet has-numbering"> Observable
<span class="hljs-keyword">call</span>: s = 语文
<span class="hljs-keyword">call</span>: s = 数学
<span class="hljs-keyword">call</span>: s = 英语
 Observable
<span class="hljs-keyword">call</span>: s = 化学
<span class="hljs-keyword">call</span>: s = 地理
<span class="hljs-keyword">call</span>: s = 政治<span id="transmark"></span>
</code><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li></ul><ul style="" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li></ul>

咱们还记得Observable.from嘛？
From操做符用来将某个对象转化为Observable对象

<code class="hljs cs has-numbering">  <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <T> Observable<T> <span class="hljs-title">from</span>(Iterable<? extends T> iterable) {
        <span class="hljs-keyword">return</span> create(<span class="hljs-keyword">new</span> OnSubscribeFromIterable<T>(iterable));
    }</code>