AIDL

AIDL

创建一个接口，再里面定义方法

package com.example.taidl;
interface ICalcAIDL
{
int add(int x , int y);
int min(int x , int y );
}

build一下gen目录下会生成ICalcAIDL.java文件

/*
* This file is auto-generated.  DO NOT MODIFY.
* Original file: /Users/dream/Downloads/android/androidProject/TAIDL/src/com/example/taidl/ICalcAIDL.aidl
*/
package com.example.taidl;
public interface ICalcAIDL extends android.os.IInterface
{
/** Local-side IPC implementation stub class. */
public static abstract class Stub extends android.os.Binder implements com.example.taidl.ICalcAIDL
{
private static final java.lang.String DESCRIPTOR = "com.example.taidl.ICalcAIDL";
/** Construct the stub at attach it to the interface. */
public Stub()
{
this.attachInterface(this, DESCRIPTOR);
}
/**
* Cast an IBinder object into an com.example.taidl.ICalcAIDL interface,
* generating a proxy if needed.
*/
public static com.example.taidl.ICalcAIDL asInterface(android.os.IBinder obj)
{
if ((obj==null)) {
return null;
}
android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
if (((iin!=null)&&(iin instanceof com.example.taidl.ICalcAIDL))) {
return ((com.example.taidl.ICalcAIDL)iin);
}
return new com.example.taidl.ICalcAIDL.Stub.Proxy(obj);
}
@Override 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_add:
{
data.enforceInterface(DESCRIPTOR);
int _arg0;
_arg0 = data.readInt();
int _arg1;
_arg1 = data.readInt();
int _result = this.add(_arg0, _arg1);
reply.writeNoException();
reply.writeInt(_result);
return true;
}
case TRANSACTION_min:
{
data.enforceInterface(DESCRIPTOR);
int _arg0;
_arg0 = data.readInt();
int _arg1;
_arg1 = data.readInt();
int _result = this.min(_arg0, _arg1);
reply.writeNoException();
reply.writeInt(_result);
return true;
}
}
return super.onTransact(code, data, reply, flags);
}
private static class Proxy implements com.example.taidl.ICalcAIDL
{
private android.os.IBinder mRemote;
Proxy(android.os.IBinder remote)
{
mRemote = remote;
}
@Override public android.os.IBinder asBinder()
{
return mRemote;
}
public java.lang.String getInterfaceDescriptor()
{
return DESCRIPTOR;
}
@Override public int add(int x, int y) throws android.os.RemoteException
{
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
int _result;
try {
_data.writeInterfaceToken(DESCRIPTOR);
_data.writeInt(x);
_data.writeInt(y);
mRemote.transact(Stub.TRANSACTION_add, _data, _reply, 0);
_reply.readException();
_result = _reply.readInt();
}
finally {
_reply.recycle();
_data.recycle();
}
return _result;
}
@Override public int min(int x, int y) throws android.os.RemoteException
{
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
int _result;
try {
_data.writeInterfaceToken(DESCRIPTOR);
_data.writeInt(x);
_data.writeInt(y);
mRemote.transact(Stub.TRANSACTION_min, _data, _reply, 0);
_reply.readException();
_result = _reply.readInt();
}
finally {
_reply.recycle();
_data.recycle();
}
return _result;
}
}
static final int TRANSACTION_add = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
static final int TRANSACTION_min = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1);
}
public int add(int x, int y) throws android.os.RemoteException;
public int min(int x, int y) throws android.os.RemoteException;
}

新建一个Service

package com.example.taidl;

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

public class CalcService extends Service{

private static final String TAG = "server";

public void onCreate()
{
Log.e(TAG, "onCreate");
}

public IBinder onBind(Intent t)
{
Log.e(TAG, "onBind");
return mBinder;
}

public void onDestroy()
{
Log.e(TAG, "onDestroy");
super.onDestroy();
}

public boolean onUnbind(Intent intent)
{
Log.e(TAG, "onUnbind");
return super.onUnbind(intent);
}

public void onRebind(Intent intent)
{
Log.e(TAG, "onRebind");
super.onRebind(intent);
}
private final ICalcAIDL.Stub mBinder = new ICalcAIDL.Stub() {

@Override
public int min(int x, int y) throws RemoteException {
return x + y;
}

@Override
public int add(int x, int y) throws RemoteException {
// TODO Auto-generated method stub
return x - y;
}
};

}

创建了一个mBinder对象，并在Service的onBind方法中返回

注册：

<service android:name="com.example.taidl.CalcService">
<intent-filter>
<action android:name="com.example.taidl.calc" />

<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</service>

我们一会会在别的应用程序中通过Intent来查找此Service；这个不需要Activity，所以我也就没写Activity，安装完成也看不到安装图标，悄悄在后台运行着。服务端编写完毕。下面开始编写客户端:

package com.example.tclient;

import com.example.taidl.ICalcAIDL;

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.util.Log;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends Activity {

private ICalcAIDL mCalcAidl;

private ServiceConnection mServiceConn = new ServiceConnection()
{
@Override
public void onServiceDisconnected(ComponentName name)
{
Log.e("client", "onServiceDisconnected");
mCalcAidl = null;
}

@Override
public void onServiceConnected(ComponentName name, IBinder service)
{
Log.e("client", "onServiceConnected");
mCalcAidl = ICalcAIDL.Stub.asInterface(service);
}
};

@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

}

/**
* 点击BindService按钮时调用
* @param view
*/
public void bindService(View view)
{
Intent intent = new Intent();
intent.setAction("com.example.taidl.calc");
bindService(intent, mServiceConn, Context.BIND_AUTO_CREATE);
}
/**
* 点击unBindService按钮时调用
* @param view
*/
public void unbindService(View view)
{
unbindService(mServiceConn);
}
/**
* 点击12+12按钮时调用
* @param view
*/
public void addInvoked(View view) throws Exception
{

if (mCalcAidl != null)
{
int addRes = mCalcAidl.add(12, 12);
Toast.makeText(this, addRes + "", Toast.LENGTH_SHORT).show();
} else
{
Toast.makeText(this, "服务器被异常杀死，请重新绑定服务端", Toast.LENGTH_SHORT)
.show();

}

}
/**
* 点击50-12按钮时调用
* @param view
*/
public void minInvoked(View view) throws Exception
{

if (mCalcAidl != null)
{
int addRes = mCalcAidl.min(50, 12);
Toast.makeText(this, addRes + "", Toast.LENGTH_SHORT).show();
} else
{
Toast.makeText(this, "服务器未绑定或被异常杀死，请重新绑定服务端", Toast.LENGTH_SHORT)
.show();

}

}
}

将服务端的aidl文件完整的复制过来，包名一定要一致。

分析AIDL生成的代码

服务端

private final ICalcAIDL.Stub mBinder = new ICalcAIDL.Stub()
{

@Override
public int add(int x, int y) throws RemoteException
{
return x + y;
}

@Override
public int min(int x, int y) throws RemoteException
{
return x - y;
}

};

ICalcAILD.Stub来执行的，让我们来看看Stub这个类的声明：

public static abstract class Stub extends android.os.Binder implements com.zhy.calc.aidl.ICalcAIDL

清楚的看到这个类是Binder的子类，是不是符合我们文章开通所说的服务端其实是一个Binder类的实例 接下来看它的onTransact()方法：

@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_add:
{
data.enforceInterface(DESCRIPTOR);
int _arg0;
_arg0 = data.readInt();
int _arg1;
_arg1 = data.readInt();
int _result = this.add(_arg0, _arg1);
reply.writeNoException();
reply.writeInt(_result);
return true;
}
case TRANSACTION_min:
{
data.enforceInterface(DESCRIPTOR);
int _arg0;
_arg0 = data.readInt();
int _arg1;
_arg1 = data.readInt();
int _result = this.min(_arg0, _arg1);
reply.writeNoException();
reply.writeInt(_result);
return true;
}
}
return super.onTransact(code, data, reply, flags);
}

文章开头也说到服务端的Binder实例会根据客户端依靠Binder驱动发来的消息，执行onTransact方法，然后由其参数决定执行服务端的代码。 可以看到onTransact有四个参数 code ， data ，replay ， flags
code 是一个整形的唯一标识，用于区分执行哪个方法，客户端会传递此参数，告诉服务端执行哪个方法
data客户端传递过来的参数
replay服务器返回回去的值
flags标明是否有返回值，0为有（双向），1为没有（单向）

我们仔细看case TRANSACTION_min中的代码

data.enforceInterface(DESCRIPTOR);

与客户端的writeInterfaceToken对用，标识远程服务的名称

int _arg0;
_arg0 = data.readInt();
int _arg1;
_arg1 = data.readInt();

接下来分别读取了客户端传入的两个参数

int _result = this.min(_arg0, _arg1);
reply.writeNoException();
reply.writeInt(_result);

然后执行this.min，即我们实现的min方法；返回result由reply写回。

add同理，可以看到服务端通过AIDL生成Stub的类，封装了服务端本来需要写的代码。

客户端

客户端主要通过ServiceConnected与服务端连接

private ServiceConnection mServiceConn = new ServiceConnection()
{
@Override
public void onServiceDisconnected(ComponentName name)
{
Log.e("client", "onServiceDisconnected");
mCalcAidl = null;
}

@Override
public void onServiceConnected(ComponentName name, IBinder service)
{
Log.e("client", "onServiceConnected");
mCalcAidl = ICalcAIDL.Stub.asInterface(service);
}
};

如果你比较敏锐，应该会猜到这个onServiceConnected中的IBinder实例，其实就是我们文章开通所说的Binder驱动，也是一个Binder实例 在ICalcAIDL.Stub.asInterface中最终调用了：

return new com.zhy.calc.aidl.ICalcAIDL.Stub.Proxy(obj);

这个Proxy实例传入了我们的Binder驱动，并且封装了我们调用服务端的代码，文章开头说，客户端会通过Binder驱动的transact()方法调用服务端代码

直接看Proxy中的add方法

@Override public int add(int x, int y) throws android.os.RemoteException
{
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
int _result;
try {
_data.writeInterfaceToken(DESCRIPTOR);
_data.writeInt(x);
_data.writeInt(y);
mRemote.transact(Stub.TRANSACTION_add, _data, _reply, 0);
_reply.readException();
_result = _reply.readInt();
}
finally {
_reply.recycle();
_data.recycle();
}
return _result;
}

首先声明两个Parcel对象，一个用于传递数据，一个用户接收返回的数据

_data.writeInterfaceToken(DESCRIPTOR);与服务器端的enforceInterfac对应
_data.writeInt(x);
_data.writeInt(y);写入需要传递的参数
mRemote.transact(Stub.TRANSACTION_add, _data, _reply, 0);

终于看到了我们的transact方法，第一个对应服务端的code,_data,_repay分别对应服务端的data，reply，0表示是双向的

_reply.readException();
_result = _reply.readInt();

最后读出我们服务端返回的数据，然后return。可以看到和服务端的onTransact基本是一行一行对应的。

我们已经通过AIDL生成的代码解释了Android Binder框架的工作原理。Service的作用其实就是为我们创建Binder驱动，即服务端与客户端连接的桥梁。