RxJava响应式编程之初级了解
据说现在流行的开发模式是 Retrofit+RxJava+MVP+ButterKnife
如果想要简单学习ButterKnife、MVP模式，可以参考我以前的例子
使用butterknife注解框架
Android—MVP设计模式高级（三）
今天我就简单来学习下RxJava的相关知识
以前我也只是听说过RxJava，RxJava这个到底是什么东西呢？
呵呵，它其实是一个库，所以我们使用里面的方法，得需要下载库，所以我们需要在AS中进行配置
1.RxJava 地址以及添加
github地址：
https://github.com/ReactiveX/RxJava
或者
https://github.com/ReactiveX/RxAndroid
依赖库添加：
compile ‘io.reactivex:rxjava:1.1.6’
或者
compile ‘io.reactivex:rxandroid:1.2.1’
2.RxJava是什么类型的库？它的原理是什么？
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 ，概括得非常精准。
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，我们接触到的类似的这样的思路，大概有接口回调、Handler通讯、广播通讯、还有一个开源的EventBus、以及ContentPorivider里面的观察者模式、AsyncTask 我们朦胧中也许就大概了解RxJava是怎么个东西了。
RxJava 的异步实现，是通过一种扩展的观察者模式来实现的。
至于观察者我就拿ContentProvider来说吧，比如我们在一个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
<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>
比如在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,重新查询一直所有记录 </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（比如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 我们调用api方法 几乎看不到 方法里面的 分线程数据操作 它只是利用了 一种观察者的设计模式 来进行 主分线程的通讯 来进行响应操作
我们来看看RxJava的察者模式流程交互图：
与传统观察者模式不同， RxJava 的事件回调方法除了普通事件 onNext() （相当于 insert）之外，还定义了两个特殊的事件：onCompleted() 和 onError()。
我们来看下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>
我们看看create源码里面做了什么？
<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>
可以看到，这里传入了一个 OnSubscribe 对象作为参数。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。
然后在看Observer中做了什么操作？
<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 不仅把每个事件单独处理，还会把它们看做一个队列。RxJava 规定，当不会再有新的 onNext() 发出时，需要触发 onCompleted() 方法作为标志。
onError(): 事件队列异常。在事件处理过程中出异常时，onError() 会被触发，同时队列自动终止，不允许再有事件发出。
在一个正确运行的事件序列中, onCompleted() 和 onError() 有且只有一个，并且是事件序列中的最后一个。需要注意的是，onCompleted() 和 onError() 二者也是互斥的，即在队列中调用了其中一个，就不应该再调用另一个。
接下来我们将全部的代码贴出来，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>
从上可以看出，事件的处理和结果的接收都是在同一个线程里面处理的。但是，Rxjava的意义何在，异步呢？别急，看以下代码的处理，你就会发现了，异步原来是这么的简单。
异步方式
我们将上面的代码稍微改下，增加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>
我们添上如下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>
我们看下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很明显的不一样啊，说明我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，还是在主线程里面操作的。怎么样，只要添加两句话，异步立马就实现了，异步处理耗时操作，就是这么easy。
我们简单看下源码
<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作，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() 指定的是它之后的操作所在的线程。
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，那么我们接着往下看，比如我们有一组需求把一个String数组的字符串，单个打印出来，我们用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输出日志如下：
<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操作符用来将某个对象转化为Observable对象，并且依次将其内容发射出去。这个类似于just，但是just会将这个对象整个发射出去。比如说一个含有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。源码如下：
<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>
上例中还有一个叫做 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 一样， FuncX 也有多个，用于不同参数个数的方法。FuncX 和 ActionX 的区别在 FuncX 包装的是有返回值的方法。
可以看到，map() 方法将参数中的 String 对象转换成一个 Integer对象后返回，而在经过 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，是最常见的也最容易理解的变换。不过 RxJava 的变换远不止这样，它不仅可以针对事件对象，还可以针对整个事件队列，这使得 RxJava 变得非常灵活。
封装Observable一对多转换
map转换，是一对一的转换，像示例当中，我们把string转成int，但是当我们需要一对多的转换，该怎么做呢？比如说，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>
这里我们没有进行转换，直接just发送过来，没有用到转换，然后在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>
我们用转换来试试看？
这里我们用到了flatmap这一函数，按通俗的一点理解：我们首先把Student转成了Observable，然后呢，又把student.getCourses()转成string挨个打印出来，结果如下：
<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>
我们还记得Observable.from嘛？
From操作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>
静以修身，俭以养德。
posted on 2016-09-08 13:48 miaozhenzhong 阅读(156) 评论(0) 编辑 收藏 举报
