AIDL

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1. 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;}

1. 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

1. 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。