1. Create .aidl文件
   定义Service接口

Caution: AIDL 做的任何改变，都必须保持后向兼容
方法支持参数和返回值，参数和返回值可以是任意类型。
1. 所有Java原型都支持（int, long, float, char ,boolean等）
2. String
3. Charsequence
4. List,元素必须是支持的数据类型，也可是其他AIDL所申明的，或者是parcelables。同时也可使用泛型申明。实际使用ArrayList来存储元素。
5. Map，也list要求相同。但不可使用泛型，实际使用HashMap来存储。

如果要使用除以上数据的类型其他类型数据，则必须使用import进行申明。

此外，在定义接口时，还需注意的有：
1. 方法可为0个或多个参数，可返回值或者void
2. 所有非原型参数，需要方向标签，in,out,inout。
3. 所有代码注释都会被生成到java接口中，除了import和package申明之前的。
4. 只支持方法，不支持静态成员变量的申明。

案例

// 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);
}

1. 实现一个接口
   Android SDK tools会根据aidl文件自动生成一个java语言的编程接口，这个接口包含一个继承于Binder的抽象类和aidl中的接口方法实现。必须继承Stub然后实现方法。

保存到/src目录下，ADT tool 会在/gen目录下生成IBinder接口文件。注意包名。
生成的接口包含一个子类Stub, 是对接口的抽象实现。因此，需要继承该Stub，然后实现抽象方法。
其中Stub还有一个助手方法asInterface(),传递IBinder并返回stub接口实例。
实例代码如下：

private final IRemoteService.Stub mBinder = new IRemoteService.Stub() {public int getPid(){return Process.myPid();}public void basicTypes(int anInt, long aLong, boolean aBoolean,float aFloat, double aDouble, String aString) {// Does nothing}
};

Caution: 注意多线程，要确保方法是线程安全的。RPC calls 通常是同步的，所以在client调用时，请使用子线程避免hand up the main thread and encounter ANR.此外，Server端不会返回Exception。

1. Expose the interface to the clients
   继承Service，重写onBind()，然后返回Stub 类的实现，即mBinder。

public class RemoteService extends Service {@Overridepublic void onCreate() {super.onCreate();}@Overridepublic IBinder onBind(Intent intent) {// Return the interfacereturn mBinder;}
}

Client调用，如果与Server不再同一个Application下，那么需要将aidl文件拷贝到Client，并且保持包名的一致。

Passing Objects over IPC

支持Parcelable，将允许Android系统decompose objects into primitives that can be marshalled over processes, 意思就是允许Android系统将objects 解耦成primitives，而这些primitives可在进程间传递。
Step:
1. 让需要传递的类实现Parcelable接口，
2. 实现writeToParcel()方法，它将把对象的当前状态写到一个Parcel
3. 添加静态字段CREATOR，它时实现Parcelable.Creator接口。
4. create a aidl, 然后申明这个Parcelable 类。

aidl 申明Rect类代码如下：

package android.graphics;// Declare Rect so AIDL can find it and knows that it implements
// the parcelable protocol.
parcelable Rect;

接下来是Rect类实现Parcelable接口代码：

import android.os.Parcel;
import android.os.Parcelable;public final class Rect implements Parcelable {public int left;public int top;public int right;public int bottom;public static final Parcelable.Creator<Rect> CREATOR = new
Parcelable.Creator<Rect>() {public Rect createFromParcel(Parcel in) {return new Rect(in);}public Rect[] newArray(int size) {return new Rect[size];}};public Rect() {}private Rect(Parcel in) {readFromParcel(in);}public void writeToParcel(Parcel out) {out.writeInt(left);out.writeInt(top);out.writeInt(right);out.writeInt(bottom);}public void readFromParcel(Parcel in) {left = in.readInt();top = in.readInt();right = in.readInt();bottom = in.readInt();}
}

Calling an IPC Method

调用远程服务的实例，在之前的Service节中已经出现过了。这里不妨再赘上,有效长，:）

public static class Binding extends Activity {/** The primary interface we will be calling on the service. */IRemoteService mService = null;/** Another interface we use on the service. */ISecondary mSecondaryService = null;Button mKillButton;TextView mCallbackText;private boolean mIsBound;/*** Standard initialization of this activity.  Set up the UI, then wait* for the user to poke it before doing anything.*/@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.remote_service_binding);// Watch for button clicks.Button button = (Button)findViewById(R.id.bind);button.setOnClickListener(mBindListener);button = (Button)findViewById(R.id.unbind);button.setOnClickListener(mUnbindListener);mKillButton = (Button)findViewById(R.id.kill);mKillButton.setOnClickListener(mKillListener);mKillButton.setEnabled(false);mCallbackText = (TextView)findViewById(R.id.callback);mCallbackText.setText("Not attached.");}/*** Class for interacting with the main interface of the service.*/private ServiceConnection mConnection = new ServiceConnection() {public void onServiceConnected(ComponentName className,IBinder service) {// This is called when the connection with the service has been// established, giving us the service object we can use to// interact with the service.  We are communicating with our// service through an IDL interface, so get a client-side// representation of that from the raw service object.mService = IRemoteService.Stub.asInterface(service);mKillButton.setEnabled(true);mCallbackText.setText("Attached.");// We want to monitor the service for as long as we are// connected to it.try {mService.registerCallback(mCallback);} catch (RemoteException e) {// In this case the service has crashed before we could even// do anything with it; we can count on soon being// disconnected (and then reconnected if it can be restarted)// so there is no need to do anything here.}// As part of the sample, tell the user what happened.Toast.makeText(Binding.this, R.string.remote_service_connected,Toast.LENGTH_SHORT).show();}public void onServiceDisconnected(ComponentName className) {// This is called when the connection with the service has been// unexpectedly disconnected -- that is, its process crashed.mService = null;mKillButton.setEnabled(false);mCallbackText.setText("Disconnected.");// As part of the sample, tell the user what happened.Toast.makeText(Binding.this, R.string.remote_service_disconnected,Toast.LENGTH_SHORT).show();}};/*** Class for interacting with the secondary interface of the service.*/private ServiceConnection mSecondaryConnection = new ServiceConnection() {public void onServiceConnected(ComponentName className,IBinder service) {// Connecting to a secondary interface is the same as any// other interface.mSecondaryService = ISecondary.Stub.asInterface(service);mKillButton.setEnabled(true);}public void onServiceDisconnected(ComponentName className) {mSecondaryService = null;mKillButton.setEnabled(false);}};private OnClickListener mBindListener = new OnClickListener() {public void onClick(View v) {// Establish a couple connections with the service, binding// by interface names.  This allows other applications to be// installed that replace the remote service by implementing// the same interface.bindService(new Intent(IRemoteService.class.getName()),mConnection, Context.BIND_AUTO_CREATE);bindService(new Intent(ISecondary.class.getName()),mSecondaryConnection, Context.BIND_AUTO_CREATE);mIsBound = true;mCallbackText.setText("Binding.");}};private OnClickListener mUnbindListener = new OnClickListener() {public void onClick(View v) {if (mIsBound) {// If we have received the service, and hence registered with// it, then now is the time to unregister.if (mService != null) {try {mService.unregisterCallback(mCallback);} catch (RemoteException e) {// There is nothing special we need to do if the service// has crashed.}}// Detach our existing connection.unbindService(mConnection);unbindService(mSecondaryConnection);mKillButton.setEnabled(false);mIsBound = false;mCallbackText.setText("Unbinding.");}}};private OnClickListener mKillListener = new OnClickListener() {public void onClick(View v) {// To kill the process hosting our service, we need to know its// PID.  Conveniently our service has a call that will return// to us that information.if (mSecondaryService != null) {try {int pid = mSecondaryService.getPid();// Note that, though this API allows us to request to// kill any process based on its PID, the kernel will// still impose standard restrictions on which PIDs you// are actually able to kill.  Typically this means only// the process running your application and any additional// processes created by that app as shown here; packages// sharing a common UID will also be able to kill each// other's processes.Process.killProcess(pid);mCallbackText.setText("Killed service process.");} catch (RemoteException ex) {// Recover gracefully from the process hosting the// server dying.// Just for purposes of the sample, put up a notification.Toast.makeText(Binding.this,R.string.remote_call_failed,Toast.LENGTH_SHORT).show();}}}};// ----------------------------------------------------------------------// Code showing how to deal with callbacks.// ----------------------------------------------------------------------/*** This implementation is used to receive callbacks from the remote* service.*/private IRemoteServiceCallback mCallback = new IRemoteServiceCallback.Stub() {/*** This is called by the remote service regularly to tell us about* new values.  Note that IPC calls are dispatched through a thread* pool running in each process, so the code executing here will* NOT be running in our main thread like most other things -- so,* to update the UI, we need to use a Handler to hop over there.*/public void valueChanged(int value) {mHandler.sendMessage(mHandler.obtainMessage(BUMP_MSG, value, 0));}};private static final int BUMP_MSG = 1;private Handler mHandler = new Handler() {@Override public void handleMessage(Message msg) {switch (msg.what) {case BUMP_MSG:mCallbackText.setText("Received from service: " + msg.arg1);break;default:super.handleMessage(msg);}}};
}