Android AIDL理解

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>