AIDL的实现

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我相信稍微对android了解一点的人都知道Android系统进程之间是不能共享内存的。因此&＃xff0c;需要一些机制来实现不同进程之间的数据交互。Android系统采用RPC方法来实现&＃xff0c;实现RPC的服务我们称之为AIDL服务(Android Interface Definition Language&＃xff09;服务。

在这里我们将提供服务的一个应用程序称之为服务端&＃xff0c;接受服务的一方叫做客户端。你首先得在服务端定义一个aidl文件&＃xff0c;如下所示&＃xff1a;

// IMyService.aidl package com.weiweishen.docs.aidl; interface IMyService{ String getValue(); }

然后重新编译程序&＃xff0c;系统会在gen目录自动生成一个IMyService.java文件&＃xff0c;你不需要改动它&＃xff0c;源代码如下&＃xff1a;

//IMyService.java /** This file is auto-generated. DO NOT MODIFY.* Original file: /Users/wei/Documents/work/Docs/src/com/weiweishen/docs/aidl/IMyService.aidl*/ package com.weiweishen.docs.aidl; public interface IMyService extends android.os.IInterface { /** Local-side IPC implementation stub class. */ public static abstract class Stub extends android.os.Binder implements com.weiweishen.docs.aidl.IMyService { private static final java.lang.String DESCRIPTOR &＃61; "com.weiweishen.docs.aidl.IMyService"; /** Construct the stub at attach it to the interface. */ public Stub() { this.attachInterface(this, DESCRIPTOR); } /*** Cast an IBinder object into an com.weiweishen.docs.aidl.IMyService interface,* generating a proxy if needed.*/ public static com.weiweishen.docs.aidl.IMyService asInterface(android.os.IBinder obj) { if ((obj&＃61;&＃61;null)) { return null; } android.os.IInterface iin &＃61; obj.queryLocalInterface(DESCRIPTOR); if (((iin!&＃61;null)&&(iin instanceof com.weiweishen.docs.aidl.IMyService))) { return ((com.weiweishen.docs.aidl.IMyService)iin); } return new com.weiweishen.docs.aidl.IMyService.Stub.Proxy(obj); } &＃64;Override public android.os.IBinder asBinder() { return this; } &＃64;Override public boolean onTransact(int code, android.os.Parcel data, android.os.Parcel reply, int flags) throws android.os.RemoteException { switch (code) { case INTERFACE_TRANSACTION: { reply.writeString(DESCRIPTOR); return true; } case TRANSACTION_getValue: { data.enforceInterface(DESCRIPTOR); java.lang.String _result &＃61; this.getValue(); reply.writeNoException(); reply.writeString(_result); return true; } } return super.onTransact(code, data, reply, flags); } private static class Proxy implements com.weiweishen.docs.aidl.IMyService { private android.os.IBinder mRemote; Proxy(android.os.IBinder remote) { mRemote &＃61; remote; } &＃64;Override public android.os.IBinder asBinder() { return mRemote; } public java.lang.String getInterfaceDescriptor() { return DESCRIPTOR; } &＃64;Override public java.lang.String getValue() throws android.os.RemoteException { android.os.Parcel _data &＃61; android.os.Parcel.obtain(); android.os.Parcel _reply &＃61; android.os.Parcel.obtain(); java.lang.String _result; try { _data.writeInterfaceToken(DESCRIPTOR); mRemote.transact(Stub.TRANSACTION_getValue, _data, _reply, 0); _reply.readException(); _result &＃61; _reply.readString(); } finally { _reply.recycle(); _data.recycle(); } return _result; } } static final int TRANSACTION_getValue &＃61; (android.os.IBinder.FIRST_CALL_TRANSACTION &＃43; 0); } public java.lang.String getValue() throws android.os.RemoteException; }

这个步骤完成之后&＃xff0c;你就可以通过继承IMyService.Stub(继承自Binder类&＃xff0c;Android本质上利用Binder实现进程之间的交互&＃xff09;来实现提供服务的具体方法。

//IMyService.java package com.weiweishen.docs; import android.app.Service; import android.content.Intent; import android.os.IBinder; import android.os.RemoteException; import com.weiweishen.docs.aidl.IMyService;; public class MyService extends Service {int i &＃61; 1;public MyService() {}public class MyServiceImpl extends IMyService.Stub{&＃64;Overridepublic String getValue() throws RemoteException {// TODO Auto-generated method stubi &＃43;&＃43; ;return "hello everyone " &＃43; i;}}&＃64;Overridepublic IBinder onBind(Intent intent) {return new MyServiceImpl();} }

我们看上面代码&＃xff0c;MyServiceImpl继承了IMyService.Stub。getValue()方法是我们提供给客户端的服务&＃xff0c;在这里我们是返回一个字符串给客户端。onBinder方法返回一个Binder类&＃xff0c;即我们继承IMyService.stub的MyServiceImpl的内部类。实现了这一步&＃xff0c;我们服务器端的代码就写好了&＃xff0c;下面我们看看客户端&＃xff0c;另建一个android project&＃xff0c;将IMyService文件连同包目录拷贝到客户端工程的src目录中&＃xff0c;看下图&＃xff0c;然后在MainActivity实现跨进程调用。

下面是MainActivity的代码&＃xff1a;

//MainActivity.java package com.weiweishen.docsclient; import com.weiweishen.docs.aidl.IMyService; import android.app.Activity; import android.content.ComponentName; import android.content.Context; import android.content.Intent; import android.content.ServiceConnection; import android.os.Bundle; import android.os.IBinder; import android.os.RemoteException; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.Toast; public class MainActivity extends Activity implements OnClickListener{IMyService myService &＃61; null;Button btn1;Button btn2;Button btn3;&＃64;Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);btn1 &＃61; (Button)findViewById(R.id.button1);btn2 &＃61;(Button)findViewById(R.id.button2);btn3 &＃61;(Button)findViewById(R.id.button3);btn1.setOnClickListener(this);btn2.setOnClickListener(this);btn3.setOnClickListener(this);}private ServiceConnection serviceConnection &＃61; new ServiceConnection() {&＃64;Overridepublic void onServiceDisconnected(ComponentName name) {// TODO Auto-generated method stub}&＃64;Overridepublic void onServiceConnected(ComponentName name, IBinder service) {// TODO Auto-generated method stubmyService &＃61; IMyService.Stub.asInterface(service);}};&＃64;Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}&＃64;Overridepublic boolean onOptionsItemSelected(MenuItem item) {// Handle action bar item clicks here. The action bar will// automatically handle clicks on the Home/Up button, so long// as you specify a parent activity in AndroidManifest.xml.int id &＃61; item.getItemId();if (id &＃61;&＃61; R.id.action_settings) {return true;}return super.onOptionsItemSelected(item);}&＃64;Overridepublic void onClick(View v) {// TODO Auto-generated method stubswitch (v.getId()) {case R.id.button1:bindService(new Intent("com.weiweishen.docs.aidl.IMyService"), serviceConnection, Context.BIND_AUTO_CREATE);break;case R.id.button2:try {Toast.makeText(MainActivity.this, myService.getValue(), Toast.LENGTH_LONG).show();} catch (RemoteException e) {// TODO Auto-generated catch blocke.printStackTrace();}break;case R.id.button3:unbindService(serviceConnection);break;default:break;}} }