android IntentService和ResultReceiver的异步处理

IntentService和ResultReceiver的异步处理

1.在下载手机上从网络下载东西的时候会用到AsyncTask来方便处理，这里可以在用IntentService和ResultReceiver

对一些基本概念做一些了解：

IntentService：

IntentService是Service类的子类，用来处理异步请求。客户端可以通过startService(Intent)方法传递请求给IntentService，IntentService通过worker thread处理每个Intent对象，执行完所有的工作之后自动停止Service。

说明：worker thread处理所有通过传递过来的请求，创建一个worker queue，一次只传递一个intent到onHandleIntent中，从而不必担心多线程带来的问题。处理完毕之后自动调用stopSelf()方 法；默认实现了Onbind（）方法，返回值为null；

它是Service、HandlerThread和Handler的强强联合。具有任务队列，顺序处理，

当处理完全部任务后

模式实现了StartCommand()方法，这个方法会放到worker queue中，然后在onHandleIntent()中执行0

使用IntentService需要两个步骤：

1、写构造函数

2、复写onHandleIntent()方法

好处：处理异步请求的时候可以减少写代码的工作量，比较轻松地实现项目的需求

ResultReceiver：

Generic interface for receiving a callback result from someone. Use this by creating a subclass and implement onReceiveResult(int, android.os.Bundle), which you can then pass to others and send through IPC, and receive results they supply with send(int, android.os.Bundle).

这是API上给的解释，说白了就是处理传过来的信息。和BroadCastReceiver一样的。

2.下面给一个例子：

1).调用startService。
2).service中开始操作处理，并且通过消息告诉activity处理已经开始。
3).activity处理消息并且显示进度条(进度条就不显示了，就打印出一段话即可)
4).service完成处理并且返回给activity需要的数据。
5).activity处理数据。
6).service通过消息告诉activity处理完成，并且kill掉自己。
7).activity取得消息并且结束掉进度条。

代码如下：

QueryService：

 public class QueryService extends IntentService {

     public QueryService() {
         super("service");
     }

     public final String action = "query";
     /**
      * 进行一些网络操作，如下载文件等
      */
     @Override
     protected void onHandleIntent(Intent intent) {
         System.out.println("进了service");
         final ResultReceiver receiver = intent.getParcelableExtra("receiver");
         String command = intent.getStringExtra("command");
         Bundle bundle = new Bundle();
         bundle.putString("data", "查询到的数据 ");
         if (command.equals("query")) {
             receiver.send(1, bundle);
             try {
                 // do something with data
                 receiver.send(2, new Bundle());

             } catch (Exception e) {
                 e.printStackTrace();
                 receiver.send(3, new Bundle());

             }

         }
         this.stopSelf();
     }
 }

MainActivity：

 public class MainActivity extends Activity {

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         findViewById(R.id.button).setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 Intent intent = new Intent(MainActivity.this,
                         QueryService.class);
                 intent.putExtra("command", "query");
                 intent.putExtra("receiver", new MyResultReceiver(new Handler()));
                 MainActivity.this.startService(intent);
             }
         });
     }

     // 对主界面进行一些修改
     private class MyResultReceiver extends ResultReceiver {
         private final int QUERY = 1, DELETE = 2, ERROR = 3;

         public MyResultReceiver(Handler handler) {
             super(handler);
         }

         @Override
         protected void onReceiveResult(int resultCode, Bundle resultData) {
             super.onReceiveResult(resultCode, resultData);

             switch (resultCode) {
             case QUERY:
                 System.out.println("query+query+query+query+query"
                         + resultData.getString("data"));
                 break;
             case DELETE:

                 System.out.println("delete+delete+delete+delete+delete+delete");
                 break;
             case ERROR:
                 System.out.println("error+error+error+error+error+error+");
                 break;

             }

         }
     }

 }

运行后的效果是：

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从而可以知道顺序是：点击button -->> 启动QueryService  -->>根据传来的command执行相应功能-->> 执行完成以后发送广播给MainActivity告诉它执行后的结果-->>更新界面或则数据展示

代码下载：代码