Android  AIDL理解

AILD(Android Interface definition language)  安卓接口定义语言

很显然，它是一种android内部进程通信接口的描述语言，通过它我们可以定义进程间的通信接口。

       编译器通过*.aidl文件的描述信息生成符合通信协议的Java代码，我们无需自己去写这段繁杂的代码，只需要在需要的时候调用即可，通过这种方式我们就可以完成进程间的通信工作。

        *.aidl文件的写法和java中interface一样，但是我们需要注意的是：

       它可以引用其它aidl文件中定义的接口，但是不能够引用你的java类文件中定义的接口。

编译你的aidl文件，你的adt插件会像资源文件一样把aidl文件编译成java代码生成在gen文件夹下。

下面是一个简单的小案例：

很明显在我们跟目录下自动生成了我们的Person.java

那么 我们的Person.aidl究竟是什么样的呢

package com.jeason.aidldemo;interface Person{String speak(String name);void eat();}

编译过程我们自动生成的呢

/* * This file is auto-generated.  DO NOT MODIFY. * Original file: D:\\AndroidData\\Lock_Screen\\AIDLDemo\\src\\com\\jeason\\aidldemo\\Person.aidl */package com.jeason.aidldemo;public interface Person extends android.os.IInterface{/** Local-side IPC implementation stub class. */public static abstract class Stub extends android.os.Binder implements com.jeason.aidldemo.Person{private static final java.lang.String DESCRIPTOR = "com.jeason.aidldemo.Person";/** Construct the stub at attach it to the interface. */public Stub(){this.attachInterface(this, DESCRIPTOR);}/** * Cast an IBinder object into an com.jeason.aidldemo.Person interface, * generating a proxy if needed. */public static com.jeason.aidldemo.Person asInterface(android.os.IBinder obj){if ((obj==null)) {return null;}android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);if (((iin!=null)&&(iin instanceof com.jeason.aidldemo.Person))) {return ((com.jeason.aidldemo.Person)iin);}return new com.jeason.aidldemo.Person.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_speak:{data.enforceInterface(DESCRIPTOR);java.lang.String _arg0;_arg0 = data.readString();java.lang.String _result = this.speak(_arg0);reply.writeNoException();reply.writeString(_result);return true;}case TRANSACTION_eat:{data.enforceInterface(DESCRIPTOR);this.eat();reply.writeNoException();return true;}}return super.onTransact(code, data, reply, flags);}private static class Proxy implements com.jeason.aidldemo.Person{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 java.lang.String speak(java.lang.String name) throws android.os.RemoteException{android.os.Parcel _data = android.os.Parcel.obtain();android.os.Parcel _reply = android.os.Parcel.obtain();java.lang.String _result;try {_data.writeInterfaceToken(DESCRIPTOR);_data.writeString(name);mRemote.transact(Stub.TRANSACTION_speak, _data, _reply, 0);_reply.readException();_result = _reply.readString();}finally {_reply.recycle();_data.recycle();}return _result;}@Override public void eat() 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_eat, _data, _reply, 0);_reply.readException();}finally {_reply.recycle();_data.recycle();}}}static final int TRANSACTION_speak = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);static final int TRANSACTION_eat = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1);}public java.lang.String speak(java.lang.String name) throws android.os.RemoteException;public void eat() throws android.os.RemoteException;}

用目录的形式展示就是

很显然的我们发现 我们的aidl生成的java文件只是在我们的方法上增加了Stub这个抽象类

而Stub继承了android.os.Binder,那么毫无疑问，他就是我们进程之件通信的核心

而在Stub中我们发现asInterface这个方法将IBinder类型的对象转换成Person类型，必要的时候生成一个代理对象返回结果。这个代理对象就是Proxy

return new com.jeason.aidldemo.Person.Stub.Proxy(obj);........private static class Proxy implements com.jeason.aidldemo.Person......

而真正执行我们的函数的是onTransact，并且他是被代理Proxy调用

package com.jeason.aidlservice;import com.jeason.aidldemo.Person;import android.app.Service;import android.content.Intent;import android.os.IBinder;import android.os.RemoteException;import android.util.Log;public class MainAidlService extends Service{    Person.Stub mPerson = new Person.Stub() {                @Override        public String speak(String name) throws RemoteException {            // TODO Auto-generated method stub            Log.d("Jeason","Person -> speak()");            return "My name is"+name;        }                @Override        public void eat() throws RemoteException {            // TODO Auto-generated method stub            Log.d("Jeason","Person -> eat()");        }    };    @Override    public IBinder onBind(Intent arg0) {        // TODO Auto-generated method stub        Log.d("Jeason","MainAidlService onBind");        return mPerson;    }}

这列很明显的发现我们的Service  用来传递消息

package com.jeason.aidl;import com.jeason.aidldemo.Person;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 MainAidlActivity extends Activity implements OnClickListener {    private Button bt1,bt2;     private Person person = null;    private ServiceConnection conn = new ServiceConnection(){        @Override        public void onServiceConnected(ComponentName arg0, IBinder service) {            // TODO Auto-generated method stub            Log.d("Jeason","ServiceConnection");            person = Person.Stub.asInterface(service);        }        @Override        public void onServiceDisconnected(ComponentName arg0) {            // TODO Auto-generated method stub                    }            };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main_aidl);        Intent intent = new Intent("android.intent.action.AIDLService");          bindService(intent, conn, Context.BIND_AUTO_CREATE);                bt1 = (Button)findViewById(R.id.xx);        bt1.setOnClickListener(this);        bt2 = (Button)findViewById(R.id.zz);        bt2.setOnClickListener(this);    }    @Override    public void onClick(View view) {        // TODO Auto-generated method stub        if(view == bt1){            try {                String retVal = person.speak("Jeason");                Toast.makeText(getApplicationContext(), retVal, Toast.LENGTH_SHORT).show();            } catch (RemoteException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }        if(view == bt2){            try {                person.eat();                Toast.makeText(getApplicationContext(), "eat", Toast.LENGTH_SHORT).show();            } catch (RemoteException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }    }}

顺便给出我们的

<service android:name="com.jeason.aidlservice.MainAidlService" >            <intent-filter>                <action android:name="android.intent.action.AIDLService" />                <category android:name="android.intent.category.DEFAULT" />            </intent-filter>        </service>