1、为什么要有AIDL？

无论学什么东西，最先得弄明白为什么要有这个东西，不要说存在即是合理，存在肯定合理，但是你还是没有明白。对于AIDL有一些人的浅显概念就是，AIDL可以跨进程访问其他应用程序，和其他应用程序通讯，那我告诉你，很多技术都可以访问，如广播（应用A在AndroidManifest.xml中注册指定Action的广播）应用B发送指定Action的广播，A就能收到信息，这样也能看成不同应用之间完成了通讯（但是这种通讯是单向的）；还如ContentProvider，通过URI接口暴露数据给其他应用访问；但是这种都算不上是应用之间的通讯。可能最让人迷惑的是Android推出来了Messager,它就是完成应用之间的通讯的。那么为什么还要有AIDL呢，官方文档介绍AIDL中有这么一句话：

Note: Using AIDL is necessary only if you allow clients from different applications to access your service for IPC and want to handle multithreading in your service. If you do not need to perform concurrent IPC across different applications, you should create your interface by implementing a Binder or, if you want to perform IPC, but do not need to handle multithreading, implement your interface using a Messenger. Regardless, be sure that you understand Bound Services before implementing an AIDL.

2、AIDL使用

// IRemoteService.aidl
package com.example.android;

// Declare any non-default types here with import statements

/** Example service interface */
interface IRemoteService {
    /** Request the process ID of this service, to do evil things with it. */
    int getPid();

    /** Demonstrates some basic types that you can use as parameters
     * and return values in AIDL.
     */
    void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat,
            double aDouble, String aString);
}

package com.example.service;

import com.example.android.IRemoteService;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.Process;

public class DDService extends Service {
	@Override
	public void onCreate() {
		super.onCreate();
		System.out.println("DDService onCreate........" + "Thread: " + Thread.currentThread().getName());
	}
	@Override
	public IBinder onBind(Intent arg0) {
		System.out.println("DDService onBind");
		return mBinder;
	}

	private final IRemoteService.Stub mBinder = new IRemoteService.Stub() {
	    public int getPid(){
	    	System.out.println("Thread: " + Thread.currentThread().getName());
	    	System.out.println("DDService getPid ");
	        return Process.myPid();
	    }
	    public void basicTypes(int anInt, long aLong, boolean aBoolean,
	        float aFloat, double aDouble, String aString) {
	    	System.out.println("Thread: " + Thread.currentThread().getName());
	    	System.out.println("basicTypes aDouble: " + aDouble +" anInt: " + anInt+" aBoolean " + aBoolean+" aString " + aString);
	    }
	};

}

package com.example.aidlclient;

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.Process;
import android.os.RemoteException;
import android.view.View;

import com.example.android.IRemoteService;

public class MainActivity extends Activity {
	private IRemoteService remoteService;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    
    ServiceConnection conn = new ServiceConnection() {
		
		@Override
		public void onServiceDisconnected(ComponentName name) {
		}
		
		@Override
		public void onServiceConnected(ComponentName name, IBinder service) {
			remoteService =	IRemoteService.Stub.asInterface(service);
			try {
				int pid = remoteService.getPid();
				int currentPid = Process.myPid();
				System.out.println("currentPID: " + currentPid +"  remotePID: " + pid);
				remoteService.basicTypes(12, 1223, true, 12.2f, 12.3, "我们的爱，我明白");
			} catch (RemoteException e) {
				e.printStackTrace();
			}
			System.out.println("bind success! " + remoteService.toString());
		}
	};
		
    /**
     * 监听按钮点击
     * @param view
     */
    public void buttonClick(View view) {
    	System.out.println("begin bindService");
    	Intent intent = new Intent("duanqing.test.aidl");
    	bindService(intent, conn, Context.BIND_AUTO_CREATE);
    }

    @Override
    protected void onDestroy() {
    	super.onDestroy();
    	unbindService(conn);
    }
}