如何写一个简单的android服务

1.android服务简介

android服务的分类还是蛮多的，网上有现成的博客讲解的很好，我就不重复了，连接如下：

http://www.cnblogs.com/newcj/archive/2011/05/30/2061370.html

本文主要介绍一种常见的服务：通知栏有图标和文字的服务，既可以做自己的事情，也可以供其他activity调用，专业术语描述为 前台服务（可startService也可以bindService）

2.原理和流程

• 要创建前台服务，我们只需要提供一个通知栏图标并且调用startForeground即可
• 要让服务自己做自己的事情，很简单，在onCreate或者onStartCommand的时候起一个Thread即可
• 想要和服务通信、调用服务提供的函数，只需要在onBind的时候返回一个IBinder对象，通过IBinder对象可以获取当前Service对象的引用，有了引用就可以调用服务提供的函数了。
• 最后一条，服务要在xml里面配置        
  <service android:name="com.scott.sayhi.MyService" >
  </service>
  

3.MyService.java

 /**
  * @author scott
  *
  */
 public class MyService extends Service
 {
     private final static String TAG = "MyService";
     private NotificationManager notificationMgr;
     private boolean canRun =true;
     private String retString = null;
     //用于和外界交互
     private final IBinder binder = new MyBinder();

     public class MyBinder extends Binder
     {
         MyService getService()
         {
             return MyService.this;
         }
     }

     @Override
     public void onCreate()
     {
         Thread thr = new Thread(null, new ServiceWorker(), "BackgroundSercie");
         thr.start();
         super.onCreate();
     }

     @Override
     public IBinder onBind(Intent intent)
     {
         Log.d(TAG, String.format("on bind,intent = %s", intent.toString()));
         notificationMgr = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
         displayNotificationMessage("服务已启动");

         return binder;
     }

     @Override
     public int onStartCommand(Intent intent, int flags, int startId)
     {
         Log.d(TAG, "start action="+intent.getAction());
         notificationMgr = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
         displayNotificationMessage("服务已启动", true);
         return super.onStartCommand(intent, flags, startId);
     }

     @Override
     public void onDestroy()
     {
         stopForeground(true);
         canRun = false;
         super.onDestroy();
     }

     public String getImage(String url)
     {
         return "19";
     }

     public String getRetString()
     {
         return retString;
     }
     //loginValidate 为service提供给外部调用的函数
     public boolean loginValidate(String userName, String password) throws Exception
     {
         String uriString = "http://www.renyugang.cn/blog/admin/admin_check.jsp";
         boolean ret = false;
         Log.d("scott", "enter myservice start loginvalidate");
         try
         {
             DefaultHttpClient httpClient = new DefaultHttpClient();
             HttpResponse response;
             HttpPost httpPost = new HttpPost(uriString);
             List<NameValuePair> nvps = new ArrayList<NameValuePair>();
             nvps.add(new BasicNameValuePair("name", userName));
             nvps.add(new BasicNameValuePair("password", password));

             httpPost.setEntity(new UrlEncodedFormEntity(nvps, HTTP.UTF_8));
             response = httpClient.execute(httpPost);
             HttpEntity entity = response.getEntity();
             retString = EntityUtils.toString(entity);
             retString = str_Filter(retString);

             if (response.getStatusLine().getStatusCode() == 200)
             {
                 if(retString.equals("") == false)
                 {
                     if (retString.startsWith("用户名") == true)
                     {
                         ret = false;
                     }
                     else
                     {
                         ret = true;
                     }
                     Log.d("retcontent", retString);
                     Log.d("info", userName+password);
                     Log.d("ret", ""+ret);
                 }

             }
         }
         catch (Exception e)
         {
             throw e;
         }
         return ret;
     }

     public String str_Filter(String strSource)
     {
         String strPattern = "(?i)(\r\n|\r|\n|\n\r)";
         strSource.trim();
         Pattern p = Pattern.compile(strPattern);
         Matcher m = p.matcher(strSource);
         if (m.find())
         {
             strSource = strSource.replaceAll("(\r\n|\r|\n|\n\r)", "");
         }
         return strSource;
     }
     //为服务设置图标和文字描述
     private void displayNotificationMessage(String message, boolean isForeground)
     {
         Notification notification = new Notification(R.drawable.icon, message,
                 System.currentTimeMillis());
         PendingIntent contentIntent = PendingIntent.getActivity(this, 0,
                 new Intent(this, MyActivity.class), 0);
         notification.setLatestEventInfo(this, "My Service", message,
                 contentIntent);
         MyService.this.startForeground(R.id.app_notification_id, notification);
     }

     private void displayNotificationMessage(String message)
     {
         Notification notification = new Notification(R.drawable.icon, message,
                 System.currentTimeMillis());
         PendingIntent contentIntent = PendingIntent.getActivity(this, 0,
                 new Intent(this, MyActivity.class), 0);
         notification.setLatestEventInfo(this, "我的通知", message,
                 contentIntent);
         notificationMgr.notify(R.id.app_notification_id + 1, notification);
     }
     //ServiceWorker service自身的线程，用于做自己的事情，这里为了表示服务的确在运行，每2秒打印一次log信息。
     class ServiceWorker implements Runnable
     {
         int counter = 0;
         @Override
         public void run()
         {
             // do background processing here.....
             while(canRun)
             {
                 Log.d("scott", ""+counter);
                 counter ++;
                 try
                 {
                     Thread.sleep(2000);
                 }
                 catch (InterruptedException e)
                 {
                     e.printStackTrace();
                 }
             }
         }
     }

 }

4.如何使用服务

 private MyService mMyService;
 private ServiceConnection mServiceConnection = new ServiceConnection()
 {
     @Override
     public void onServiceDisconnected(ComponentName name)
     {
         // TODO Auto-generated method stub
     }

     @Override
     public void onServiceConnected(ComponentName name, IBinder service)
     {
         // bindService成功的时候返回service的引用
         MyBinder myBinder = (MyBinder)service;
         mMyService = myBinder.getService();
     }
 }
 //启动服务
 Intent intentService = new Intent(MyActivity.this, MyService.class);
 intentService.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 intentService.setAction("scott");
 //bindService用于和service进行交互
 MyActivity.this.bindService(intentService, mServiceConnection, BIND_AUTO_CREATE);
 //startService用于启动service但是不和其交互
 startService(intentService);