如何在Android中添加系统服务

说明：本次说的系统服务，是指捆绑在system_process进程中的服务。

  仔细阅读源码可以发现，在frameworks/base/services/java/com/Android/server/SystemServer.java中添加了很多服务，什么熵信息、电量、wife等等服务，这些服务启动都在launcher之前，一般要继承Binder或者继承一个AIDL。下面试着来添加一个简单系统服务

一。在frameworks/base/core/java/android/os/ 增加一个aidl文件，最后用aidl工具生产一个Java文件，这样可以方便后面：

 package android.os;

 /**
  * Interface that allows controlling and querying YtTts connectivity.
  *
  * {@hide}
  */
 interface IYtTtsService{
     /**
      * 播放Text文字
      */
     int speak(String text);
 }

然后在修改/frameworks/base/Android.mk，在LOCAL_SRC_FILES里添加一行：core/java/android/os/IYtTtsService.aidl \

不确定补充：把AIDL文件写在这个地方似乎可以避免加@hide

二 。在frameworks/base/services/java/com/android/server/ 新建要增加的service，继承上面aidl生产的java：

 package com.android.server;
 import android.content.Context;
 import android.os.IYtTtsService;
 import android.os.RemoteException;
 import android.util.Log;

 public class YtTtsService  extends IYtTtsService.Stub {
     private WorkerThread mWorker;
     public YtTtsService(Context context) {
         super();
         mWorker = new WorkerThread("YtTtsServiceWorker");
         mWorker.start();
         Log.i("[YT]", "In YtTtsService-->"+context);
       }
     @Override
     public int speak(String text) throws RemoteException {
         Log.i("[YT]", "In YtTtsService-->"+text);
         return 0;
     }
     private class WorkerThread extends Thread{
         int i = 0;
         public WorkerThread(String name) {
           super(name);
         }
         public void run() {
             while(true){
                 i++;
                 Log.i("[YT]", "In YtTtsService-->WorkerThread running "+i);
                 try {
                     Thread.sleep(3000);
                 } catch (InterruptedException e) {
                     e.printStackTrace();
                 }
             }
         }
     }
 }

三。在 frameworks/base/services/java/com/android/server/SystemServer.java, ServerThread中run()方法中增加代码：

 try {
     Log.i("[YT]", "In SystemServer, YtTts add..");
     ServiceManager.addService("yttts", new YtTtsService(context));
 } catch (Throwable e) {
     Log.i("[YT]", "In SystemServer, YtTts add err..");
 }

5.在/frameworks/base/core/java/cn/youngtone/tts建一个YtTtsManager类,用于管理YtTtsService ：

 package cn.youngtone.tts;

 import android.content.Context;
 import android.os.IYtTtsService;
 import android.os.RemoteException;
 import android.util.Log;

 public class YtTtsManager {
     IYtTtsService service;

     public YtTtsManager(Context context ,IYtTtsService service) {
          this.service = service;
     }
     public void speak(String text) {
         try {
             Log.e("[YT]" , "In YtTtsManage-->speak():"+text);
             service.speak(text);
         } catch (RemoteException e) {
             Log.e("[YT]" , "In YtTtsManage-->E:RemoteException");
             e.printStackTrace();
         }
     }
 }

四。 在ContextImpl getSystemService中添加代码：

 if ("yttts".equals(name)) {

     if (mYtTtsManager == null) {
        IBinder b = ServiceManager.getService("yttts");
        IYtTtsService service = IYtTtsService.Stub.asInterface(b);
        mYtTtsManager = new YtTtsManager(this, service);
      }
      return mYtTtsManager;
 }

五。测试代码

 YtTtsManager mManager = (YtTtsManager)getSystemService("yttts");
 mManager.speak("这是一个简单的系统服务!");