Android bind 回调实现Service向activity传递数据
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<p>开启服务的时候,如果我们是通过bindService来绑定服务并且要向服务传递数据,可以直接在Intent中设置bundle来达到效果,但是如果是我们需要从服务中返回一些数据到Activity中的时候,实现起来就有各种各样的方法,比如说使用回调,使用广播等等,今天说的是使用回调的方法。</p>
<p>新建一个工程,并编写一个服务:</p>
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<pre><span style="color:#008080"> 1</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> MyService <span style="color:#0000ff">extends</span><span style="color:#000000"> Service {
</span><span style="color:#008080"> 2</span> <span style="color:#0000ff">private</span> <span style="color:#0000ff">boolean</span> connecting = <span style="color:#0000ff">false</span><span style="color:#000000">;
</span><span style="color:#008080"> 3</span> <span style="color:#0000ff">private</span><span style="color:#000000"> Callback callback;
</span><span style="color:#008080"> 4</span>
<span style="color:#008080"> 5</span> <span style="color:#000000"> @Nullable
</span><span style="color:#008080"> 6</span> <span style="color:#000000"> @Override
</span><span style="color:#008080"> 7</span> <span style="color:#0000ff">public</span><span style="color:#000000"> IBinder onBind(Intent intent) {
</span><span style="color:#008080"> 8</span> <span style="color:#0000ff">return</span> <span style="color:#0000ff">new</span><span style="color:#000000"> Binder();
</span><span style="color:#008080"> 9</span> <span style="color:#000000"> }
</span><span style="color:#008080">10</span>
<span style="color:#008080">11</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> Binder <span style="color:#0000ff">extends</span><span style="color:#000000"> android.os.Binder {
</span><span style="color:#008080">12</span> <span style="color:#0000ff">public</span><span style="color:#000000"> MyService getService() {
</span><span style="color:#008080">13</span> <span style="color:#0000ff">return</span> MyService.<span style="color:#0000ff">this</span><span style="color:#000000">;
</span><span style="color:#008080">14</span> <span style="color:#000000"> }
</span><span style="color:#008080">15</span> <span style="color:#000000"> }
</span><span style="color:#008080">16</span>
<span style="color:#008080">17</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">18</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onCreate() {
</span><span style="color:#008080">19</span> <span style="color:#0000ff">super</span><span style="color:#000000">.onCreate();
</span><span style="color:#008080">20</span> connecting = <span style="color:#0000ff">true</span><span style="color:#000000">;
</span><span style="color:#008080">21</span> <span style="color:#0000ff">new</span> Thread(<span style="color:#0000ff">new</span><span style="color:#000000"> Runnable() {
</span><span style="color:#008080">22</span>
<span style="color:#008080">23</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">24</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> run() {
</span><span style="color:#008080">25</span> <span style="color:#0000ff">int</span> i = 0<span style="color:#000000">;
</span><span style="color:#008080">26</span> <span style="color:#0000ff">while</span> (connecting == <span style="color:#0000ff">true</span><span style="color:#000000">) {
</span><span style="color:#008080">27</span> i++<span style="color:#000000">;
</span><span style="color:#008080">28</span> <span style="color:#0000ff">if</span> (callback != <span style="color:#0000ff">null</span><span style="color:#000000">) {
</span><span style="color:#008080">29</span> callback.onDataChange(i + ""<span style="color:#000000">);
</span><span style="color:#008080">30</span> <span style="color:#000000"> }
</span><span style="color:#008080">31</span> <span style="color:#0000ff">try</span><span style="color:#000000"> {
</span><span style="color:#008080">32</span> Thread.sleep(1000<span style="color:#000000">);
</span><span style="color:#008080">33</span> } <span style="color:#0000ff">catch</span><span style="color:#000000"> (InterruptedException e) {
</span><span style="color:#008080">34</span> <span style="color:#000000"> e.printStackTrace();
</span><span style="color:#008080">35</span> <span style="color:#000000"> }
</span><span style="color:#008080">36</span> <span style="color:#000000"> }
</span><span style="color:#008080">37</span> <span style="color:#000000"> }
</span><span style="color:#008080">38</span> <span style="color:#000000"> }).start();
</span><span style="color:#008080">39</span> <span style="color:#000000"> }
</span><span style="color:#008080">40</span>
<span style="color:#008080">41</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> setCallback(Callback callback) {
</span><span style="color:#008080">42</span> <span style="color:#0000ff">this</span>.callback =<span style="color:#000000"> callback;
</span><span style="color:#008080">43</span> <span style="color:#000000"> }
</span><span style="color:#008080">44</span>
<span style="color:#008080">45</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">static</span> <span style="color:#0000ff">interface</span><span style="color:#000000"> Callback {
</span><span style="color:#008080">46</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onDataChange(String data);
</span><span style="color:#008080">47</span> <span style="color:#000000"> }
</span><span style="color:#008080">48</span>
<span style="color:#008080">49</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">50</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onDestroy() {
</span><span style="color:#008080">51</span> <span style="color:#0000ff">super</span><span style="color:#000000">.onDestroy();
</span><span style="color:#008080">52</span> connecting = <span style="color:#0000ff">false</span><span style="color:#000000">;
</span><span style="color:#008080">53</span> <span style="color:#000000"> }
</span><span style="color:#008080">54</span> }</pre>
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<p>在服务中的onCreate方法中,我们打开了一个线程来模拟服务的运行,并在线程每隔1s中给私有变量i赋值递增,然后我们编写了一个公有的接口Callback,并且定义了一个该接口的私有成员,并且在onCreate方法中调用了接口里面的函数onDataChange。接下来我们自定义了一个Binder的子类并在这个类中定义了函数返回当前的这个Service,这里的目的就是在Activity中可以访问到这个Service的回调接口Callback并实现该接口的方法。</p>
<p>Activity代码如下:</p>
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<pre><span style="color:#008080"> 1</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> MainActivity <span style="color:#0000ff">extends</span> AppCompatActivity <span style="color:#0000ff">implements</span><span style="color:#000000"> View.OnClickListener,
</span><span style="color:#008080"> 2</span> <span style="color:#000000"> ServiceConnection {
</span><span style="color:#008080"> 3</span>
<span style="color:#008080"> 4</span> <span style="color:#0000ff">private</span><span style="color:#000000"> TextView tvOut;
</span><span style="color:#008080"> 5</span>
<span style="color:#008080"> 6</span> <span style="color:#000000"> @Override
</span><span style="color:#008080"> 7</span> <span style="color:#0000ff">protected</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onCreate(Bundle savedInstanceState) {
</span><span style="color:#008080"> 8</span> <span style="color:#0000ff">super</span><span style="color:#000000">.onCreate(savedInstanceState);
</span><span style="color:#008080"> 9</span> <span style="color:#000000"> setContentView(R.layout.activity_main);
</span><span style="color:#008080">10</span> tvOut =<span style="color:#000000"> (TextView) findViewById(R.id.tvOut);
</span><span style="color:#008080">11</span> findViewById(R.id.btnBindService).setOnClickListener(<span style="color:#0000ff">this</span><span style="color:#000000">);
</span><span style="color:#008080">12</span> <span style="color:#000000"> }
</span><span style="color:#008080">13</span>
<span style="color:#008080">14</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">15</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onClick(View v) {
</span><span style="color:#008080">16</span> bindService(<span style="color:#0000ff">new</span> Intent(<span style="color:#0000ff">this</span>, MyService.<span style="color:#0000ff">class</span>), <span style="color:#0000ff">this</span><span style="color:#000000">, BIND_AUTO_CREATE);
</span><span style="color:#008080">17</span> <span style="color:#000000"> }
</span><span style="color:#008080">18</span>
<span style="color:#008080">19</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">20</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onServiceConnected(ComponentName name, IBinder service) {
</span><span style="color:#008080">21</span> MyService.Binder binder =<span style="color:#000000"> (MyService.Binder) service;
</span><span style="color:#008080">22</span> MyService myService =<span style="color:#000000"> binder.getService();
</span><span style="color:#008080">23</span> myService.setCallback(<span style="color:#0000ff">new</span><span style="color:#000000"> MyService.Callback() {
</span><span style="color:#008080">24</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">25</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onDataChange(String data) {
</span><span style="color:#008080">26</span> Message msg = <span style="color:#0000ff">new</span><span style="color:#000000"> Message();
</span><span style="color:#008080">27</span> msg.obj =<span style="color:#000000"> data;
</span><span style="color:#008080">28</span> <span style="color:#000000"> handler.sendMessage(msg);
</span><span style="color:#008080">29</span> <span style="color:#000000"> }
</span><span style="color:#008080">30</span> <span style="color:#000000"> });
</span><span style="color:#008080">31</span> <span style="color:#000000"> }
</span><span style="color:#008080">32</span>
<span style="color:#008080">33</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">34</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onServiceDisconnected(ComponentName name) {
</span><span style="color:#008080">35</span>
<span style="color:#008080">36</span> <span style="color:#000000"> }
</span><span style="color:#008080">37</span>
<span style="color:#008080">38</span> <span style="color:#0000ff">private</span> Handler handler = <span style="color:#0000ff">new</span><span style="color:#000000"> Handler() {
</span><span style="color:#008080">39</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">40</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> handleMessage(Message msg) {
</span><span style="color:#008080">41</span> <span style="color:#0000ff">super</span><span style="color:#000000">.handleMessage(msg);
</span><span style="color:#008080">42</span> <span style="color:#000000"> tvOut.setText(msg.obj.toString());
</span><span style="color:#008080">43</span> <span style="color:#000000"> }
</span><span style="color:#008080">44</span> <span style="color:#000000"> };
</span><span style="color:#008080">45</span> }</pre>
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<p>因为服务绑定后,会从onBind方法中返回一个Binder对象,这个对象会在onServiceConnectde方法中获取到,所以我们先从Binder对象中获取到我们从服务传递过来的MyService对象,然后调用MyService对象的setCallback方法来设置我们需要的处理逻辑,这里是把i的值打印出来,因为服务中开启了线程,所以这里也不能直接更新UI。</p>
<p> </p>
<p>总结:回调机制是Java中的一个重要特性,在Android中使用到的地方很广泛,例如我们给按钮设定点击事件等。这里的回调,其实是通过在发送端定义回调接口,并且调用接口的回调方法,然后在接收端实现该接口的方法。只要接口被调用了,就会回调接收端的被实现了的方法,这样数据就能传递过来。</p>
<p> </p>
<p>注意:开启的服务是在主线程中运行的,如果在服务中开启了线程,那么在子线程中就不能直接更新UI</p>
</div>
<p>开启服务的时候,如果我们是通过bindService来绑定服务并且要向服务传递数据,可以直接在Intent中设置bundle来达到效果,但是如果是我们需要从服务中返回一些数据到Activity中的时候,实现起来就有各种各样的方法,比如说使用回调,使用广播等等,今天说的是使用回调的方法。</p>
<p>新建一个工程,并编写一个服务:</p>
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<pre><span style="color:#008080"> 1</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> MyService <span style="color:#0000ff">extends</span><span style="color:#000000"> Service {
</span><span style="color:#008080"> 2</span> <span style="color:#0000ff">private</span> <span style="color:#0000ff">boolean</span> connecting = <span style="color:#0000ff">false</span><span style="color:#000000">;
</span><span style="color:#008080"> 3</span> <span style="color:#0000ff">private</span><span style="color:#000000"> Callback callback;
</span><span style="color:#008080"> 4</span>
<span style="color:#008080"> 5</span> <span style="color:#000000"> @Nullable
</span><span style="color:#008080"> 6</span> <span style="color:#000000"> @Override
</span><span style="color:#008080"> 7</span> <span style="color:#0000ff">public</span><span style="color:#000000"> IBinder onBind(Intent intent) {
</span><span style="color:#008080"> 8</span> <span style="color:#0000ff">return</span> <span style="color:#0000ff">new</span><span style="color:#000000"> Binder();
</span><span style="color:#008080"> 9</span> <span style="color:#000000"> }
</span><span style="color:#008080">10</span>
<span style="color:#008080">11</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> Binder <span style="color:#0000ff">extends</span><span style="color:#000000"> android.os.Binder {
</span><span style="color:#008080">12</span> <span style="color:#0000ff">public</span><span style="color:#000000"> MyService getService() {
</span><span style="color:#008080">13</span> <span style="color:#0000ff">return</span> MyService.<span style="color:#0000ff">this</span><span style="color:#000000">;
</span><span style="color:#008080">14</span> <span style="color:#000000"> }
</span><span style="color:#008080">15</span> <span style="color:#000000"> }
</span><span style="color:#008080">16</span>
<span style="color:#008080">17</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">18</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onCreate() {
</span><span style="color:#008080">19</span> <span style="color:#0000ff">super</span><span style="color:#000000">.onCreate();
</span><span style="color:#008080">20</span> connecting = <span style="color:#0000ff">true</span><span style="color:#000000">;
</span><span style="color:#008080">21</span> <span style="color:#0000ff">new</span> Thread(<span style="color:#0000ff">new</span><span style="color:#000000"> Runnable() {
</span><span style="color:#008080">22</span>
<span style="color:#008080">23</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">24</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> run() {
</span><span style="color:#008080">25</span> <span style="color:#0000ff">int</span> i = 0<span style="color:#000000">;
</span><span style="color:#008080">26</span> <span style="color:#0000ff">while</span> (connecting == <span style="color:#0000ff">true</span><span style="color:#000000">) {
</span><span style="color:#008080">27</span> i++<span style="color:#000000">;
</span><span style="color:#008080">28</span> <span style="color:#0000ff">if</span> (callback != <span style="color:#0000ff">null</span><span style="color:#000000">) {
</span><span style="color:#008080">29</span> callback.onDataChange(i + ""<span style="color:#000000">);
</span><span style="color:#008080">30</span> <span style="color:#000000"> }
</span><span style="color:#008080">31</span> <span style="color:#0000ff">try</span><span style="color:#000000"> {
</span><span style="color:#008080">32</span> Thread.sleep(1000<span style="color:#000000">);
</span><span style="color:#008080">33</span> } <span style="color:#0000ff">catch</span><span style="color:#000000"> (InterruptedException e) {
</span><span style="color:#008080">34</span> <span style="color:#000000"> e.printStackTrace();
</span><span style="color:#008080">35</span> <span style="color:#000000"> }
</span><span style="color:#008080">36</span> <span style="color:#000000"> }
</span><span style="color:#008080">37</span> <span style="color:#000000"> }
</span><span style="color:#008080">38</span> <span style="color:#000000"> }).start();
</span><span style="color:#008080">39</span> <span style="color:#000000"> }
</span><span style="color:#008080">40</span>
<span style="color:#008080">41</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> setCallback(Callback callback) {
</span><span style="color:#008080">42</span> <span style="color:#0000ff">this</span>.callback =<span style="color:#000000"> callback;
</span><span style="color:#008080">43</span> <span style="color:#000000"> }
</span><span style="color:#008080">44</span>
<span style="color:#008080">45</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">static</span> <span style="color:#0000ff">interface</span><span style="color:#000000"> Callback {
</span><span style="color:#008080">46</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onDataChange(String data);
</span><span style="color:#008080">47</span> <span style="color:#000000"> }
</span><span style="color:#008080">48</span>
<span style="color:#008080">49</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">50</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onDestroy() {
</span><span style="color:#008080">51</span> <span style="color:#0000ff">super</span><span style="color:#000000">.onDestroy();
</span><span style="color:#008080">52</span> connecting = <span style="color:#0000ff">false</span><span style="color:#000000">;
</span><span style="color:#008080">53</span> <span style="color:#000000"> }
</span><span style="color:#008080">54</span> }</pre>
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<p>在服务中的onCreate方法中,我们打开了一个线程来模拟服务的运行,并在线程每隔1s中给私有变量i赋值递增,然后我们编写了一个公有的接口Callback,并且定义了一个该接口的私有成员,并且在onCreate方法中调用了接口里面的函数onDataChange。接下来我们自定义了一个Binder的子类并在这个类中定义了函数返回当前的这个Service,这里的目的就是在Activity中可以访问到这个Service的回调接口Callback并实现该接口的方法。</p>
<p>Activity代码如下:</p>
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<pre><span style="color:#008080"> 1</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> MainActivity <span style="color:#0000ff">extends</span> AppCompatActivity <span style="color:#0000ff">implements</span><span style="color:#000000"> View.OnClickListener,
</span><span style="color:#008080"> 2</span> <span style="color:#000000"> ServiceConnection {
</span><span style="color:#008080"> 3</span>
<span style="color:#008080"> 4</span> <span style="color:#0000ff">private</span><span style="color:#000000"> TextView tvOut;
</span><span style="color:#008080"> 5</span>
<span style="color:#008080"> 6</span> <span style="color:#000000"> @Override
</span><span style="color:#008080"> 7</span> <span style="color:#0000ff">protected</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onCreate(Bundle savedInstanceState) {
</span><span style="color:#008080"> 8</span> <span style="color:#0000ff">super</span><span style="color:#000000">.onCreate(savedInstanceState);
</span><span style="color:#008080"> 9</span> <span style="color:#000000"> setContentView(R.layout.activity_main);
</span><span style="color:#008080">10</span> tvOut =<span style="color:#000000"> (TextView) findViewById(R.id.tvOut);
</span><span style="color:#008080">11</span> findViewById(R.id.btnBindService).setOnClickListener(<span style="color:#0000ff">this</span><span style="color:#000000">);
</span><span style="color:#008080">12</span> <span style="color:#000000"> }
</span><span style="color:#008080">13</span>
<span style="color:#008080">14</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">15</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onClick(View v) {
</span><span style="color:#008080">16</span> bindService(<span style="color:#0000ff">new</span> Intent(<span style="color:#0000ff">this</span>, MyService.<span style="color:#0000ff">class</span>), <span style="color:#0000ff">this</span><span style="color:#000000">, BIND_AUTO_CREATE);
</span><span style="color:#008080">17</span> <span style="color:#000000"> }
</span><span style="color:#008080">18</span>
<span style="color:#008080">19</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">20</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onServiceConnected(ComponentName name, IBinder service) {
</span><span style="color:#008080">21</span> MyService.Binder binder =<span style="color:#000000"> (MyService.Binder) service;
</span><span style="color:#008080">22</span> MyService myService =<span style="color:#000000"> binder.getService();
</span><span style="color:#008080">23</span> myService.setCallback(<span style="color:#0000ff">new</span><span style="color:#000000"> MyService.Callback() {
</span><span style="color:#008080">24</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">25</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onDataChange(String data) {
</span><span style="color:#008080">26</span> Message msg = <span style="color:#0000ff">new</span><span style="color:#000000"> Message();
</span><span style="color:#008080">27</span> msg.obj =<span style="color:#000000"> data;
</span><span style="color:#008080">28</span> <span style="color:#000000"> handler.sendMessage(msg);
</span><span style="color:#008080">29</span> <span style="color:#000000"> }
</span><span style="color:#008080">30</span> <span style="color:#000000"> });
</span><span style="color:#008080">31</span> <span style="color:#000000"> }
</span><span style="color:#008080">32</span>
<span style="color:#008080">33</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">34</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> onServiceDisconnected(ComponentName name) {
</span><span style="color:#008080">35</span>
<span style="color:#008080">36</span> <span style="color:#000000"> }
</span><span style="color:#008080">37</span>
<span style="color:#008080">38</span> <span style="color:#0000ff">private</span> Handler handler = <span style="color:#0000ff">new</span><span style="color:#000000"> Handler() {
</span><span style="color:#008080">39</span> <span style="color:#000000"> @Override
</span><span style="color:#008080">40</span> <span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span><span style="color:#000000"> handleMessage(Message msg) {
</span><span style="color:#008080">41</span> <span style="color:#0000ff">super</span><span style="color:#000000">.handleMessage(msg);
</span><span style="color:#008080">42</span> <span style="color:#000000"> tvOut.setText(msg.obj.toString());
</span><span style="color:#008080">43</span> <span style="color:#000000"> }
</span><span style="color:#008080">44</span> <span style="color:#000000"> };
</span><span style="color:#008080">45</span> }</pre>
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<p>因为服务绑定后,会从onBind方法中返回一个Binder对象,这个对象会在onServiceConnectde方法中获取到,所以我们先从Binder对象中获取到我们从服务传递过来的MyService对象,然后调用MyService对象的setCallback方法来设置我们需要的处理逻辑,这里是把i的值打印出来,因为服务中开启了线程,所以这里也不能直接更新UI。</p>
<p> </p>
<p>总结:回调机制是Java中的一个重要特性,在Android中使用到的地方很广泛,例如我们给按钮设定点击事件等。这里的回调,其实是通过在发送端定义回调接口,并且调用接口的回调方法,然后在接收端实现该接口的方法。只要接口被调用了,就会回调接收端的被实现了的方法,这样数据就能传递过来。</p>
<p> </p>
<p>注意:开启的服务是在主线程中运行的,如果在服务中开启了线程,那么在子线程中就不能直接更新UI</p>
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