Android平台的跨进程通信——AIDL（上）

什么是AIDL

AIDL:Android Interface Definition Language,即Android接口定义语言。Android系统中的进程之间不能共享内存，因此，需要提供一些机制在不同进程之间进行数据通信，AIDL应运而生。

有些Android小伙伴也许就不服了，认为用Intent不就可以了？跳转Activity 和发送BroadCast都可以用intent传递数据。Content Provider的功能更是毋庸置疑。如:获取手机联系人就是系统应用提供的接口。关于Content Provider的原理在后续文章中会讲解。那么只剩Service，机智的小伙伴已经猜想到AIDL就和Service有关。

AIDL开发步骤

• 定义aidl文件
• 定义Service
• 实现客户端

关于更多AIDL的概念还请自行Google。虽说实践要和理论结合，把那千篇一律的理论粘贴过来，不符合笔者的风格也浪费读者的时间。喜欢上图、上代码，够简单够粗暴……

新建AIDL文件

• 定义了AIDLDemo 和AIDLDemoService两个工程
• 两个工程里的aidl文件相同，并且是在同名目录下。会对应生成java文件。

根据aidl文件生成的java类，eclipse在gen目录下，AndroidStudio在app/build目录下。

/* * This file is auto-generated.  DO NOT MODIFY. * Original file: /AIDLDemo/src/com/flueky/aidl/FluekyAidlInterface.aidl */package com.flueky.aidl;// Declare any non-default types here with import statementspublic interface FluekyAidlInterface extends android.os.IInterface{/** Local-side IPC implementation stub class. */public static abstract class Stub extends android.os.Binder implements com.flueky.aidl.FluekyAidlInterface{private static final java.lang.String DESCRIPTOR = "com.flueky.aidl.FluekyAidlInterface";/** Construct the stub at attach it to the interface. */public Stub(){this.attachInterface(this, DESCRIPTOR);}/** * Cast an IBinder object into an com.flueky.aidl.FluekyAidlInterface interface, * generating a proxy if needed. */public static com.flueky.aidl.FluekyAidlInterface asInterface(android.os.IBinder obj){if ((obj==null)) {return null;}android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);if (((iin!=null)&&(iin instanceof com.flueky.aidl.FluekyAidlInterface))) {return ((com.flueky.aidl.FluekyAidlInterface)iin);}return new com.flueky.aidl.FluekyAidlInterface.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_basicTypes:{data.enforceInterface(DESCRIPTOR);int _arg0;_arg0 = data.readInt();long _arg1;_arg1 = data.readLong();boolean _arg2;_arg2 = (0!=data.readInt());float _arg3;_arg3 = data.readFloat();double _arg4;_arg4 = data.readDouble();java.lang.String _arg5;_arg5 = data.readString();this.basicTypes(_arg0, _arg1, _arg2, _arg3, _arg4, _arg5);reply.writeNoException();return true;}}return super.onTransact(code, data, reply, flags);}private static class Proxy implements com.flueky.aidl.FluekyAidlInterface{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;}/**     * Demonstrates some basic types that you can use as parameters     * and return values in AIDL.     */@Override public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, java.lang.String aString) 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.writeInt(anInt);_data.writeLong(aLong);_data.writeInt(((aBoolean)?(1):(0)));_data.writeFloat(aFloat);_data.writeDouble(aDouble);_data.writeString(aString);mRemote.transact(Stub.TRANSACTION_basicTypes, _data, _reply, 0);_reply.readException();}finally {_reply.recycle();_data.recycle();}}}static final int TRANSACTION_basicTypes = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);}/**     * Demonstrates some basic types that you can use as parameters     * and return values in AIDL.     */public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, java.lang.String aString) throws android.os.RemoteException;}

分析代码段记住如下三点：
1. 内部类：Stub
2. 静态方法：asInterface
3. aidl文件里声明的方法（这里指basicTypes）

写Server端

AidlService类

package com.flueky.aidldemoservice;import android.app.Service;import android.content.Intent;import android.os.IBinder;import android.os.RemoteException;import android.util.Log;import com.flueky.aidl.FluekyAidlInterface;public class AidlService extends Service {    public AidlService() {    }    @Override    public IBinder onBind(Intent intent) {        return new Stub();    }    private class Stub extends FluekyAidlInterface.Stub {        /**         * Demonstrates some basic types that you can use as parameters         * and return values in AIDL.         *         * @param anInt         * @param aLong         * @param aBoolean         * @param aFloat         * @param aDouble         * @param aString         */        @Override        public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, String aString) throws RemoteException {            Log.d("TAG", anInt + " " + aLong + " " + aBoolean + " " + aFloat + " " + aDouble + " " + aString);        }    }}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.flueky.aidldemoservice">    <application        android:allowBackup="true"        android:icon="@mipmap/ic_launcher"        android:label="@string/app_name"        android:supportsRtl="true"        android:theme="@style/AppTheme">        <service            android:name=".AidlService"            android:enabled="true"            android:exported="true">            <intent-filter>                <action android:name="com.flueky.aidl.action.aidl"/>            </intent-filter>        </service>    </application></manifest>

记住Server端的包名com.flueky.aidldemoservice和AidlService的action com.flueky.aidl.action.aidl。

写client端

MainActivity类

package com.flueky.aidldemo;import com.flueky.aidl.FluekyAidlInterface;import android.app.Activity;import android.app.Service;import android.content.ComponentName;import android.content.Intent;import android.content.ServiceConnection;import android.os.Bundle;import android.os.IBinder;import android.os.RemoteException;import android.util.Log;public class MainActivity extends Activity {    private FluekyAidlInterface aidlInterface;    private ServiceConnection conn = new ServiceConnection() {        @Override        public void onServiceDisconnected(ComponentName name) {        }        @Override        public void onServiceConnected(ComponentName name, IBinder service) {            // 获取aidl对象            aidlInterface = FluekyAidlInterface.Stub.asInterface(service);            try {                Log.d("TAG", "开始调用");                aidlInterface.basicTypes(1, 2, false, 1.2f, 1.3, "flueky");                Log.d("TAG", "调用结束");            } catch (RemoteException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        Intent intent = new Intent("com.flueky.aidl.action.aidl");        // android 5.0 不支持隐式跳转，需要指定包名        intent.setPackage("com.flueky.aidldemoservice");        // 绑定服务        bindService(intent, conn, Service.BIND_AUTO_CREATE);    }    @Override    protected void onDestroy() {        super.onDestroy();        unbindService(conn);    }}

• 在MainActivity中通过action 和应用包名（Android 5.0以上不支持隐式跳转）绑定AIDL的Service。
• 通过静态方法asInterface 获取aidl接口的实例。
• 通过实例调用在aidl文件中声明的方法。

检查结果

关键代码块

            // 获取aidl对象            aidlInterface = FluekyAidlInterface.Stub.asInterface(service);            try {                Log.d("TAG", "开始调用");                aidlInterface.basicTypes(1, 2, false, 1.2f, 1.3, "flueky");                Log.d("TAG", "调用结束");            } catch (RemoteException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }

        @Override        public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, String aString) throws RemoteException {            Log.d("TAG", anInt + " " + aLong + " " + aBoolean + " " + aFloat + " " + aDouble + " " + aString);        }

分析运行结果，已成功将基本类型数据传递至Server端，关于传递对象数据和Sever端将数据传回Client端，将在下一篇讲解。