看过的写的比较好的service之AIDL

本文将以一个例子来和你分享使用AIDL的基础技能，这个例子里有：

1、一个类mAIDLActivity，继承Activity。里面有三个按钮，text分别为StartService，StopService，CallbackTest。

2、一个类mAIDLService，继承Service。为了充分展示ADIL的功能，它做以下工作：当用户点击CallbackTest按钮时，从mAIDLActivity调用mAIDLService中的Stub
对象的一个方法invokCallBack()，而这个方法又会调用mAIDLActivity中Stub
对象的一个方法performAction()，这个方法在屏幕上显示一个toast。没什么意义，只是展示一下AIDL如何使用。

3、两个AIDL文件：forService.aidl和forActivity.aidl。对应名字，在Service和Activity中分别有对象需要用到它们定义的接口。

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

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package com.styleflying.AIDL;

interface forActivity {

void performAction();

}

package com.styleflying.AIDL;
interface forActivity {
void performAction();
}

文件：forService.aidl

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package com.styleflying.AIDL;

import com.styleflying.AIDL.forActivity;

interface forService {

void registerTestCall(forActivity cb);

void invokCallBack();

}

package com.styleflying.AIDL;
import com.styleflying.AIDL.forActivity;
interface forService {
void registerTestCall(forActivity cb);
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：

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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

{

public static abstract class Stub extends android.os.Binder implements com.styleflying.AIDL.forActivity

{

private static final java.lang.String DESCRIPTOR = "com.styleflying.AIDL.forActivity";

public Stub()

{

this.attachInterface(this, DESCRIPTOR);

}

public static com.styleflying.AIDL.forActivity asInterface(android.os.IBinder obj)

{

if ((obj==null)) {

return null;

}

android.os.IInterface iin = (android.os.IInterface)obj.queryLocalInterface(DESCRIPTOR);

if (((iin!=null)&&(iin instanceof com.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;

}

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
{

public static abstract class Stub extends android.os.Binder implements com.styleflying.AIDL.forActivity
{
private static final java.lang.String DESCRIPTOR = "com.styleflying.AIDL.forActivity";

public Stub()
{
this.attachInterface(this, DESCRIPTOR);
}

public static com.styleflying.AIDL.forActivity asInterface(android.os.IBinder obj)
{
if ((obj==null)) {
return null;
}
android.os.IInterface iin = (android.os.IInterface)obj.queryLocalInterface(DESCRIPTOR);
if (((iin!=null)&&(iin instanceof com.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：

[java] view
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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

{

public static abstract class Stub extends android.os.Binder implements com.styleflying.AIDL.forService

{

private static final java.lang.String DESCRIPTOR = "com.styleflying.AIDL.forService";

public Stub()

{

this.attachInterface(this, DESCRIPTOR);

}

public static com.styleflying.AIDL.forService asInterface(android.os.IBinder obj)

{

if ((obj==null)) {

return null;

}

android.os.IInterface iin = (android.os.IInterface)obj.queryLocalInterface(DESCRIPTOR);

if (((iin!=null)&&(iin instanceof com.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();

return true;

}

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;

}

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
{

public static abstract class Stub extends android.os.Binder implements com.styleflying.AIDL.forService
{
private static final java.lang.String DESCRIPTOR = "com.styleflying.AIDL.forService";

public Stub()
{
this.attachInterface(this, DESCRIPTOR);
}

public static com.styleflying.AIDL.forService asInterface(android.os.IBinder obj)
{
if ((obj==null)) {
return null;
}
android.os.IInterface iin = (android.os.IInterface)obj.queryLocalInterface(DESCRIPTOR);
if (((iin!=null)&&(iin instanceof com.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();
return true;
}
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:

[java] view
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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() {

@Override

public void onClick(View v)

{

try

{

mService.invokCallBack();

} catch (RemoteException e)

{

// TODO Auto-generated catch block

e.printStackTrace();

}

}

});

}

}

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() {

@Override
public void onClick(View v)
{
try
{
mService.invokCallBack();
} catch (RemoteException e)
{
// TODO Auto-generated catch block
e.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:

[java] view
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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() {

@Override

public void invokCallBack() throws RemoteException

{

callback.performAction();

}

@Override

public void registerTestCall(forActivity cb) throws RemoteException

{

callback = cb;

}

};

}

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() {
@Override
public void invokCallBack() throws RemoteException
{
callback.performAction();

}
@Override
public 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。

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）。