android进程间通信：使用AIDL
开发环境为Eclipse。
拣重要的先说，来看看aidl文件的内容：
文件：forActivity.aidl
view plaincopy to clipboardprint?package com.styleflying.AIDL;interface ITaskCallback {void performAction();?
文件：forService.aidl
view plaincopy to clipboardprint?package com.styleflying.AIDL;import com.styleflying.AIDL.forActivity;interface ITaskBinder {void registerTestCall(ITaskCallback tc);void invokCallBack();}
这两个文件和Java文件放置的地方一样，看包名。
在Eclipse中它们将被自动编译为forActivity.java和forService.java，它们存放在gen目录下。为了方便手头无法演练的读者，代码贴上，不用细看。
文件forActivity.java：
view plaincopy to clipboardprint?/** This file is auto-generated. DO NOT MODIFY. * Original file:D:\\workspace\\AIDLTest\\src\\com\\styleflying\\AIDL\\forActivity.aidl*/package com.styleflying.AIDL;import java.lang.String;import android.os.RemoteException;import android.os.IBinder;import android.os.IInterface;import android.os.Binder;import android.os.Parcel;public interface forActivity extends android.os.IInterface{/** Local-side IPC implementation stub class. */public static abstract class Stub extends android.os.Binder implementscom.styleflying.AIDL.forActivity{private static final java.lang.String DESCRIPTOR ="com.styleflying.AIDL.forActivity";/** Construct the stub at attach it to the interface. */public Stub(){this.attachInterface(this, DESCRIPTOR);}/** * Cast an IBinder object into an forActivity interface, *generating a proxy if needed. */public static com.styleflying.AIDL.forActivityasInterface(android.os.IBinder obj){if ((obj==null)) {return null;}android.os.IInterface iin =(android.os.IInterface)obj.queryLocalInterface(DESCRIPTOR);if (((iin!=null)&&(iin instanceofcom.styleflying.AIDL.forActivity))) {return ((com.styleflying.AIDL.forActivity)iin);}return new com.styleflying.AIDL.forActivity.Stub.Proxy(obj);}public android.os.IBinder asBinder(){return this;}@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_performAction:{data.enforceInterface(DESCRIPTOR);this.performAction();reply.writeNoException();return true;}}return super.onTransact(code, data, reply, flags);}private static class Proxy implements com.styleflying.AIDL.forActivity{private android.os.IBinder mRemote;Proxy(android.os.IBinder remote){mRemote = remote;}public android.os.IBinder asBinder(){return mRemote;}public java.lang.String getInterfaceDescriptor(){return DESCRIPTOR;}public void performAction() throws android.os.RemoteException{android.os.Parcel _data = android.os.Parcel.obtain();android.os.Parcel _reply = android.os.Parcel.obtain();try {_data.writeInterfaceToken(DESCRIPTOR);mRemote.transact(Stub.TRANSACTION_performAction, _data, _reply, 0);_reply.readException();}finally {_reply.recycle();_data.recycle();}}}static final int TRANSACTION_performAction =(IBinder.FIRST_CALL_TRANSACTION + 0);}public void performAction() throws android.os.RemoteException;}
文件forService.java：
+ expand sourceview plaincopy to clipboardprint?·········10········20········30········40········50········60········70········80········90········100·······110·······120·······130·······140·······150/** This file is auto-generated. DO NOT MODIFY. * Original file:D:\\workspace\\AIDLTest\\src\\com\\styleflying\\AIDL\\forService.aidl*/package com.styleflying.AIDL;import java.lang.String;import android.os.RemoteException;import android.os.IBinder;import android.os.IInterface;import android.os.Binder;import android.os.Parcel;public interface forService extends android.os.IInterface{/** Local-side IPC implementation stub class. */public static abstract class Stub extends android.os.Binder implementscom.styleflying.AIDL.forService{private static final java.lang.String DESCRIPTOR ="com.styleflying.AIDL.forService";/** Construct the stub at attach it to the interface. */public Stub(){this.attachInterface(this, DESCRIPTOR);}/** * Cast an IBinder object into an forService interface, * generatinga proxy if needed. */public static com.styleflying.AIDL.forServiceasInterface(android.os.IBinder obj){if ((obj==null)) {return null;}android.os.IInterface iin =(android.os.IInterface)obj.queryLocalInterface(DESCRIPTOR);if (((iin!=null)&&(iin instanceofcom.styleflying.AIDL.forService))) {return ((com.styleflying.AIDL.forService)iin);}return new com.styleflying.AIDL.forService.Stub.Proxy(obj);}public android.os.IBinder asBinder(){return this;}@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_registerTestCall:{data.enforceInterface(DESCRIPTOR);com.styleflying.AIDL.forActivity _arg0;_arg0 =com.styleflying.AIDL.forActivity.Stub.asInterface(data.readStrongBinder());this.registerTestCall(_arg0);reply.writeNoException();returntrue;}case TRANSACTION_invokCallBack:{data.enforceInterface(DESCRIPTOR);this.invokCallBack();reply.writeNoException();return true;}}return super.onTransact(code, data, reply, flags);}private static class Proxy implements com.styleflying.AIDL.forService{private android.os.IBinder mRemote;Proxy(android.os.IBinder remote){mRemote = remote;}public android.os.IBinder asBinder(){return mRemote;}public java.lang.String getInterfaceDescriptor(){return DESCRIPTOR;}public void registerTestCall(com.styleflying.AIDL.forActivity cb)throws android.os.RemoteException{android.os.Parcel _data = android.os.Parcel.obtain();android.os.Parcel _reply = android.os.Parcel.obtain();try {_data.writeInterfaceToken(DESCRIPTOR);_data.writeStrongBinder((((cb!=null))?(cb.asBinder()):(null)));mRemote.transact(Stub.TRANSACTION_registerTestCall, _data, _reply, 0);_reply.readException();}finally {_reply.recycle();_data.recycle();}}public void invokCallBack() throws android.os.RemoteException{android.os.Parcel _data = android.os.Parcel.obtain();android.os.Parcel _reply = android.os.Parcel.obtain();try {_data.writeInterfaceToken(DESCRIPTOR);mRemote.transact(Stub.TRANSACTION_invokCallBack, _data, _reply, 0);_reply.readException();}finally {_reply.recycle();_data.recycle();}}}static final int TRANSACTION_registerTestCall =(IBinder.FIRST_CALL_TRANSACTION + 0);static final int TRANSACTION_invokCallBack =(IBinder.FIRST_CALL_TRANSACTION + 1);}public void registerTestCall(com.styleflying.AIDL.forActivity cb)throws android.os.RemoteException;public void invokCallBack() throws android.os.RemoteException;}
两段代码差不多，前面基本一样，从后面看，最后跟着我们在AIDL中自定义的方法，没有实现。两个文件各定义一个了接口，这两个接口分别会在Activity和Service中使用，在那里我们将实现自定义的方法。两个接口中都定义了一个抽象类Stub，实现所在的接口。Stub中又有一个类Proxy。Stub中有一个static的asInterface()方法，里面有很多return语句，在mAIDLActivity中调用它时，它返回一个新创建的内部类Proxy对象。
这个Stub对我们来说很有用，它继承了Binder。Binder有什么用呢？一个类，继承了Binder，那么它的对象就可以被远程的进程使用了(前提是远程进程获取了这个类的对象【对象的引用】，至于如如何获得看下文)，在本例中就是说，如果一个Service中有一个继承了Stub的类的对象，那么这个对象中的方法就可以在Activity中使用，对Activity也是这样。至于Binder的细节，网上有很多贴介绍，看不明白也不影响我们完成这个例子。
再看mAIDLActivity.java:
view plaincopy to clipboardprint?package com.styleflying.AIDL;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.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.Toast;public class mAIDLActivity extends Activity {private static final String TAG = "AIDLActivity";private Button btnOk; private Button btnCancel; private Button btnCallBack; private void Log(String str) { Log.d(TAG, "------ " + str + "------"); } private forActivity mCallback = new forActivity.Stub() {public void performAction() throws RemoteException{Toast.makeText(mAIDLActivity.this, "this toast is called from service", 1).show();}};forService mService;private ServiceConnection mConnection = new ServiceConnection() {public void onServiceConnected(ComponentName className,IBinder service) {mService = forService.Stub.asInterface(service);try {mService.registerTestCall(mCallback);}catch (RemoteException e) {}}public void onServiceDisconnected(ComponentName className) {Log("disconnect service");mService = null;}}; @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.main); btnOk = (Button)findViewById(R.id.btn_ok); btnCancel = (Button)findViewById(R.id.btn_cancel); btnCallBack = (Button)findViewById(R.id.btn_callback); btnOk.setOnClickListener(new OnClickListener() { public void onClick(View v) { Bundle args = new Bundle(); Intent intent = new Intent(mAIDLActivity.this, mAIDLService.class); intent.putExtras(args); bindService(intent, mConnection, Context.BIND_AUTO_CREATE); startService(intent); } }); btnCancel.setOnClickListener(new OnClickListener() { public void onClick(View v) { unbindService(mConnection); //stopService(intent); } }); btnCallBack.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v){try{mService.invokCallBack();} catch (RemoteException e){// TODO Auto-generated catch blocke.printStackTrace();}}}); }}
很短，相信大家很容易看明白。注意mConnection，它的onServiceConnected()中有一句mService =forService.Stub.asInterface(service);给mService赋值了，这个mService是一个forService，而service是onServiceConnected()传进来的参数，onServiceConnected()会在连接Service的时候被系统调用，这个service参数的值来自哪里呢？看mAIDLService.java:
view plaincopy to clipboardprint?package com.styleflying.AIDL;import android.app.Service;import android.content.Intent;import android.os.IBinder;import android.os.RemoteCallbackList;import android.os.RemoteException;import android.util.Log;public class mAIDLService extends Service { private static final String TAG = "AIDLService"; private forActivity callback; private void Log(String str) { Log.d(TAG, "------ " + str + "------"); } @Override public void onCreate() { Log("service create"); } @Override public void onStart(Intent intent, int startId) { Log("service start id=" + startId); } @Override public IBinder onBind(Intent t) { Log("service on bind"); return mBinder; } @Override public void onDestroy() { Log("service on destroy"); super.onDestroy(); } @Override public boolean onUnbind(Intent intent) { Log("service on unbind"); return super.onUnbind(intent); } public void onRebind(Intent intent) { Log("service on rebind"); super.onRebind(intent); } private final forService.Stub mBinder = new forService.Stub() {@Overridepublic void invokCallBack() throws RemoteException{callback.performAction();}@Overridepublic void registerTestCall(forActivity cb) throws RemoteException{callback = cb;} };}
注意onBind()，它的返回类型为IBinder，返回了一个mBinder，看看mBinder的定义：
??? private final forService.Stub mBinder = new forService.Stub() {
??????? @Override
??? ??? public void invokCallBack() throws RemoteException
??? ??? {
??? ??? ??? callback.performAction();
??? ???? }
??????? @Override
??? ??? public void registerTestCall(forActivity cb) throws RemoteException
??? ??? {
??? ??? ??? callback = cb;
??????? }
?????? };
它是实现了我们在AIDL中定义的方法，这个mBinder最终返回给了mAIDLActivity中的mService，于是在mAIDLActivity中可以使用mBinder中的方法了。在mAIDLActivity中也有一个类似mBinder的对象，看看定义： ??
??????? private forActivity mCallback = new forActivity.Stub()
??? {
?? ??? ?public void performAction() throws RemoteException
?? ??? ?{
?? ??? ??? ?Toast.makeText(mAIDLActivity.this, "this toast is called from service", 1).show();
?? ??? ?}
?? ?? };
我们要在界面上显示一个toast，就是在这里实现的。这个对象，在mConnection的onServiceConnected()被调用时，通过调用mService（也就是远程的mAIDLService中的mBinder）的registerTestCall()，传递给了mAIDLService，于是在mAIDLService中可以调用performAction()了。
很啰嗦，只为了能把这个细节说清楚。请大家认真看，我尽量避免错别字、混乱的大小写和逻辑不清的语法，相信你会看明白。是不是很简单？再啰嗦一下，做一个大致总结，我们使用AIDL是要做什么呢：
让Acticity（或者说一个进程/一个类？）和Service（或者说远端进程/远端类/对象？）获取对方的一个Stub对象，这个对象在定义时实现了我们在AIDL中定义的方法，于是这些远程对象中的方法可以在本地使用了。如果这种使用（通信）是单向的，比如只是Activity需要通知Service做什么，那么只要Service中有一个Stub对象，并且传给Acticity就够了。
至于如何获得远程的Stub，参看上面的代码，看mConnection、registerTestCall、onRebind，它们展示了一种方法。
另外，有时候我们可能在一个类中有多个Stub对象，它们都要给远程交互的类的实例，这个时候可以考虑使用RemoteCallbackList<>（docs/reference/android/os/RemoteCallbackList.html）。
欢迎阅读、收藏本文。例子随手写的，功能只在演示AIDL的使用。您可以转载本文，但请勿盲目乱贴。不是我小气，我不权威，我怕它被贴到泛滥，以讹传讹，害了人。
