Service相关--读书笔记

2013-12-30 18:16:11

1. Service和Activty都是从Context里面派生出来的，因此都可以直接调用getResource()，getContentResolver()等方法。

2. 启动Service有两种方式：

2.1 startService()：该方法启动Service，访问者和Service之间没有关联，一旦启动，即使访问者退出，Service依然运行；

2.2 bindService()：该方法启动Service，访问者和Service绑定在一起，一旦访问者退出，Service随即退出。

3. onCreate()只会被调用一次，onStartCommand()方法每次Service被启动时都会被调用。

4. 绑定本地Service并与之通信：

4.1 当程序通过startService()、stopService()来启动、停止Service时，Service和访问者之间无法进行通信和数据交换。

4.2 如果要实现访问者和Service之间通信、交换数据，那么需要使用bindService()和unBindService()来启动、停止Service。

5. 程序实例：

先来一张图：

MyService.java

 package com.example.localservice;

 import android.app.Service;
 import android.content.Intent;
 import android.os.Binder;
 import android.os.IBinder;
 import android.util.Log;

 public class MyService extends Service {
     private int i;
     private MyBinder myBinder;

     // Define our own Binder class
     public class MyBinder extends Binder {
         // Any methods you can defined.
         public int getValue() {
             return i;
         }
     }

     @Override
     public void onCreate() {
         // Something the service doing.
         super.onCreate();
         myBinder = new MyBinder();
         new Thread() {
             public void run() {
                 while (true) {
                     try {
                         Thread.sleep(1000);
                     } catch (InterruptedException e) {
                         e.printStackTrace();
                     }
                     i++;
                 }
             };
         }.start();
     }

     // Return our own Binder object.
     @Override
     public IBinder onBind(Intent intent) {
         return myBinder;
     }

     @Override
     public boolean onUnbind(Intent intent) {
         Log.d("David", "intent = " + intent);
         return super.onUnbind(intent);
     }

     @Override
     public void onDestroy() {
         Log.d("David", "-------onDestroy!");
         super.onDestroy();
     }

 }

MainActivity.java

 package com.example.localservice;

 import android.app.Activity;
 import android.content.ComponentName;
 import android.content.Intent;
 import android.content.ServiceConnection;
 import android.os.Bundle;
 import android.os.IBinder;
 import android.util.Log;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.Toast;

 import com.example.localservice.MyService.MyBinder;

 public class MainActivity extends Activity {
     private MyBinder myBinder;
     private Button btnBindService;
     private Button btnUnbindService;
     private Button btnGetValue;

     ServiceConnection connection = new ServiceConnection() {

         // Two call-back methods.
         @Override
         public void onServiceDisconnected(ComponentName name) {
             Log.d("David", "ServiceDisconnected!");
         }

         @Override
         public void onServiceConnected(ComponentName name, IBinder service) {
             Log.d("David", "ServiceConnected!");
             myBinder = (MyBinder) service;
         }
     };

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         btnBindService = (Button) findViewById(R.id.btn_bind_service);
         btnUnbindService = (Button) findViewById(R.id.btn_unbind_service);
         btnUnbindService.setEnabled(false);
         btnGetValue = (Button) findViewById(R.id.btn_get_value);
         btnGetValue.setEnabled(false);
         btnBindService.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 Intent intent = new Intent("android.intent.action.DAVID");
                 bindService(intent, connection, BIND_AUTO_CREATE); // Bind service with connection.
                 Log.d("David", "Bind service!");
                 btnUnbindService.setEnabled(true);
                 btnGetValue.setEnabled(true);
             }
         });

         btnUnbindService.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 if (connection != null) {
                     // stopService(new Intent("android.intent.action.DAVID"));
                     unbindService(connection);
                     Log.d("David", "Unbind service!");
                 }
             }
         });

         btnGetValue.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 if (myBinder == null) {
                     Toast.makeText(MainActivity.this,
                             "Please bind service first!", Toast.LENGTH_LONG)
                             .show();
                     return;
                 }
                 Log.d("David", "Got value = " + myBinder.getValue());
             }
         });
     }

 }

代码和操作很简单，看button title即可。源码下载

遇到一个问题：先Bind service，然后点击第三个button，发现可以取到值，此时点击第二个button，unbind service，再点击第三个button发现还是能取到值，这个还得在研究研究，当然了，有知道答案的言语一声。

6. Android的远程调用

Android的远程调用和Java的RMI类似，一样都是先定义一个远程调用接口，然后为该接口提供一个实现类即可。与RMI不同的是，客户端访问Service时，Android并不是直接返回Serivce对象给客户端，而是将一个回调对象IBinder通过onBind()方法返回给客户端。

7. 本地调用Serivce，onBind()方法返回的是IBinder对象，远程调用返回的是IBinder对象的代理。

程序实例：Server端

IServer.aidl

 package com.example.serviceserver;

 interface IServer{
    String getColor();
 }

ServiceServer.java

 package com.example.serviceserver;

 import android.app.Service;
 import android.content.Intent;
 import android.os.IBinder;
 import android.os.RemoteException;

 public class ServiceServer extends Service {
     private int i;
     private StringBuffer sBuffer = new StringBuffer("ServiceServer");
     private MyBinder myBinder;

     public class MyBinder extends IServer.Stub {

         @Override
         public String getColor() throws RemoteException {
             return sBuffer.toString();
         }

     }

     @Override
     public void onCreate() {
         super.onCreate();
         myBinder = new MyBinder();
         new Thread() {
             public void run() {
                 while (true) {
                     try {
                         Thread.sleep(1000);
                     } catch (InterruptedException e) {
                         e.printStackTrace();
                     }
                     sBuffer.append(i + "");
                     i++;
                 }
             };
         }.start();
     }

     @Override
     public IBinder onBind(Intent intent) {
         return myBinder;
     }
 }

Client端：

IServer.aidl

 package com.example.serviceserver;

 interface IServer{
    String getColor();
 }

MainActivity.java

 package com.example.serviceclient;

 import android.app.Activity;
 import android.content.ComponentName;
 import android.content.Intent;
 import android.content.ServiceConnection;
 import android.os.Bundle;
 import android.os.IBinder;
 import android.os.RemoteException;
 import android.util.Log;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.Toast;

 import com.example.serviceserver.IServer;

 public class MainActivity extends Activity {
     private IServer myBinder;
     private Button btnBindService;
     private Button btnUnbindService;
     private Button btnGetValue;

     ServiceConnection connection = new ServiceConnection() {

         // Two call-back methods.
         @Override
         public void onServiceDisconnected(ComponentName name) {
             Log.d("David", "ServiceDisconnected!");
         }

         @Override
         public void onServiceConnected(ComponentName name, IBinder service) {
             Log.d("David", "ServiceConnected!");
             myBinder = IServer.Stub.asInterface(service);
         }
     };

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         btnBindService = (Button) findViewById(R.id.btn_bind_service);
         btnUnbindService = (Button) findViewById(R.id.btn_unbind_service);
         btnUnbindService.setEnabled(false);
         btnGetValue = (Button) findViewById(R.id.btn_get_value);
         btnGetValue.setEnabled(false);
         btnBindService.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 Intent intent = new Intent("android.intent.action.main.DAVID");
                 bindService(intent, connection, BIND_AUTO_CREATE); // Bind
                 Log.d("David", "Bind service!");
                 btnUnbindService.setEnabled(true);
                 btnGetValue.setEnabled(true);
             }
         });

         btnUnbindService.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 if (connection != null) {
                     // stopService(new Intent("android.intent.action.DAVID"));
                     unbindService(connection);
                     Log.d("David", "Unbind service!");
                 }
             }
         });

         btnGetValue.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 if (myBinder == null) {
                     Toast.makeText(MainActivity.this,
                             "Please bind service first!", Toast.LENGTH_LONG)
                             .show();
                     return;
                 }
                 try {
                     Log.d("David", "Got value = " + myBinder.getColor());
                 } catch (RemoteException e) {
                     e.printStackTrace();
                 }
             }
         });
     }

 }

还是这个问题：先Bind service，然后点击第三个button，发现可以取到值，此时点击第二个button，unbind service，再点击第三个button发现还是能取到值。有知道的同学欢迎拍砖。

源码下载

先运行SeriviceServer，然后再启动ServiceClient，比较简单，留做笔记吧，希望对同学们有帮助。