Android之AIDL知识总结

1.AIDL介绍

　　AIDL是一个缩写，全称是Android Interface Definition Language，翻译为Android接口定义语言。主要用于线程之间的通信，本文主要以不同应用之间使用AIDL通信为例介绍AIDL。

2.AIDL的使用

　　AIDL的使用按照AIDL文件类型分类，一种是序列化数据类，需要实现Parcelable，另一种是定义方法接口，以供系统使用来完成跨进程通信的。

　　AIDL默认支持JAVA的八种基本数据类型、String、CharSequence、List类型、Map类型。

2.1. 数据类实现Parcelable

　　Message.aidl文件

// Message.aidl
package com.zhangmiao.aidlservice;

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

parcelable Message;

　　Message.java文件

package com.zhangmiao.aidlservice;

import android.os.Parcel;
import android.os.Parcelable;

/**
* Created by zhangmiao on 2017/4/19.
*/

public class Message implements Parcelable {
protected int status;
protected String content;

public int getStatus() {
return status;
}

public void setStatus(int status) {
this.status = status;
}

public String getContent() {
return content;
}

public void setContent(String content) {
this.content = content;
}

public Message(int status, String content){
this.status = status;
this.content = content;
}

public Message(Parcel parcel){
status = parcel.readInt();
content = parcel.readString();
}

public final static Creator<Message> CREATOR = new Creator<Message>() {
@Override
public Message createFromParcel(Parcel source) {
return new Message(source);
}

@Override
public Message[] newArray(int size) {
return new Message[size];
}
};

@Override
public int describeContents() {
return 0;
}

@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(status);
dest.writeString(content);
}

@Override
public String toString() {
return "status : "+status + ",content : "+content;
}
}

2.2.定义方法接口　　

　　MessageManager.aidl文件

// MessageManager.aidl
package com.zhangmiao.aidlservice;

// Declare any non-default types here with import statements
import com.zhangmiao.aidlservice.Message;
interface MessageManager {
List<Message> getMessages();
void addMessage(in Message message);
}

2.3.移植aidl与java文件

　　将服务端的Message.aidl、MessageManager.aidl与Message.java文件移植到客户端项目中，注意文件的包名要保持一致，不可不同。下图是项目结构图。

2.4.编写服务器代码

package com.zhangmiao.aidlservice;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.RemoteException;
import android.support.annotation.Nullable;

import java.util.ArrayList;
import java.util.List;

/**
* Created by zhangmiao on 2017/4/19.
*/

public class AIDLService extends Service {
private final static String TAG = AIDLService.class.getSimpleName();
private List<Message> mMessageList = new ArrayList<>();
private final MessageManager.Stub messageService = new MessageManager.Stub() {

@Override
public List<Message> getMessages() throws RemoteException {
if(mMessageList != null) {
return mMessageList;
}
return new ArrayList<>();
}

@Override
public void addMessage(Message message) throws RemoteException {
if(mMessageList == null){
mMessageList = new ArrayList<>();
}
mMessageList.add(message);
}
};

@Override
public void onCreate() {
super.onCreate();
Message message1 = new Message(1,"open");
mMessageList.add(message1);
Message message2 = new Message(2,"get");
mMessageList.add(message2);
}

@Nullable
@Override
public IBinder onBind(Intent intent) {
return messageService;
}
}

　　修改服务器的AndroidManifest.xml文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.zhangmiao.aidlservice">

<application android:allowBackup="true" android:icon="@mipmap/ic_launcher"
android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true" android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:name=".AIDLService"
android:exported="true">
<intent-filter>
<action android:name="com.zhangmiao.service.aidlservice" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</service>
</application>

</manifest>

2.5.编写客户端代码

package com.zhangmiao.aidldemo;

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.support.v7.app.AppCompatActivity;
import android.util.Log;
import com.zhangmiao.aidlservice.Message;
import com.zhangmiao.aidlservice.MessageManager;

import java.util.List;

public class MainActivity extends AppCompatActivity {

private final static String TAG = MainActivity.class.getSimpleName();

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent intent = new Intent();
intent.setPackage("com.zhangmiao.aidlservice");
intent.setAction("com.zhangmiao.service.aidlservice");
bindService(intent, mServiceConnection, Context.BIND_AUTO_CREATE);
}

private ServiceConnection mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
Log.d(TAG,"ServiceConnection onServiceConnected");
MessageManager messageManager = MessageManager.Stub.asInterface(service);
try {
List<Message> messages = messageManager.getMessages();
for(int i = 0;i<messages.size();i++){
Log.d(TAG,"get Message for MessageManager:"+messages.get(i).toString());
}
}catch (RemoteException e){
e.printStackTrace();
}
}
@Override
public void onServiceDisconnected(ComponentName name) {
Log.d(TAG,"ServiceConnection onServiceDisconnected");
}
};
}

　　运行结果如图：

3.AIDL继承

　　在AIDL的序列化数据类的时候，有时候数据类有很多，并且是有继承关系的，这个时候直接使用是有问题的，需要处理一下。

3.1.错误做法

3.1.1.添加ConnectMessage类

　　ConnectMessage.aidl文件

// ConnectMessage.aidl
package com.zhangmiao.aidlservice;

// Declare any non-default types here with import statements
parcelable ConnectMessage;

　　ConnectMessage.java文件

package com.zhangmiao.aidlservice;
import android.os.Parcel;
/**
* Created by zhangmiao on 2017/4/25.
*/
public class ConnectMessage extends Message {
protected int  isConnect;
public ConnectMessage(int status,String content,int isConnect){
super(status,content);
this.isConnect = isConnect;
}
public ConnectMessage(Parcel parcel){
super(parcel);
isConnect = parcel.readInt();
}
public final static Creator<ConnectMessage> CREATOR = new Creator<ConnectMessage>() {
@Override
public ConnectMessage createFromParcel(Parcel source) {
return new ConnectMessage(source);
}
@Override
public ConnectMessage[] newArray(int size) {
return new ConnectMessage[size];
}
};
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(status);
dest.writeString(content);
dest.writeInt(isConnect);
}
@Override
public String toString() {
return "status : "+status + ",content : "+content+",isConnect : "+isConnect;
}
}

　　注意：客户端与服务端ConnectMessage的aidl文件与java文件都需要添加。

3.1.2 在服务端发送ConnnectMessage消息。

　　修改AIDLService类中的onCreate（）方法：

@Override
public void onCreate() {
super.onCreate();
Message message1 = new Message(1,"open");
mMessageList.add(message1);
Message message2 = new Message(2,"get");
mMessageList.add(message2);
Message connMessage = new ConnectMessage(3,"conn",1);
mMessageList.add(connMessage);
}

3.1.3.在客户端接收ConnnectMessage消息。

　　修改客户端的MainActivity的ServiceConnect对象的实现。

private ServiceConnection mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
Log.d(TAG,"ServiceConnection onServiceConnected");
MessageManager messageManager = MessageManager.Stub.asInterface(service);
try {
List<Message> messages = messageManager.getMessages();
for(int i = 0;i<messages.size();i++){
if(messages.get(i).getStatus() == 3){
　　　　　　ConnectMessage connectMessage = (ConnectMessage)message;
　　　　　　Log.d(TAG,"get conn Message for MessageManager:"+connectMessage.toString());
　　　　　　break;
　　　　}
　　　　Log.d(TAG,"get Message for MessageManager:"+message.toString());
　　　　}
}catch (RemoteException e){
e.printStackTrace();
}
}

@Override
public void onServiceDisconnected(ComponentName name) {
Log.d(TAG,"ServiceConnection onServiceDisconnected");
}
};

　　这个时候运行就会出现如下错误：

04-26 11:43:20.998 2567-2567/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.zhangmiao.aidldemo, PID: 2567 java.lang.ClassCastException: com.zhangmiao.aidlservice.Message cannot be cast to com.zhangmiao.aidlservice.ConnectMessage
at com.zhangmiao.aidldemo.MainActivity$1.onServiceConnected(MainActivity.java:42)
at android.app.LoadedApk$ServiceDispatcher.doConnected(LoadedApk.java:1101)
at android.app.LoadedApk$ServiceDispatcher$RunConnection.run(LoadedApk.java:1118)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5095)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602)
at dalvik.system.NativeStart.main(Native Method)

3.2.正确做法　

　　在java中，用子类对象初始化父类，可以将父类强制转换成引用的子类，这样使用是没有问题的，但是在AIDL使用中，在服务器端用子类对象初始化父类，在服务器端将父类强制转换成引用的子类这样是没有问题的，但是在客户端这样强制转换时不可以的，因为客户端只是将父类当做父类，如果还是想要在客户端进行父类强制转换成引用的子类，可以借助序列化中的parcel对象进行实现。

　　实现方法如下：

3.2.1.实现一个Message的替换类MessageSub类。

　　MessageSub.aidl文件：

package com.zhangmiao.aidlservice;

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

parcelable MessageSub;

　　MessageSub.java文件：

package com.zhangmiao.aidlservice;

import android.os.Parcel;
import android.os.Parcelable;

/**
* Created by zhangmiao on 2017/4/26.
*/

public class MessageSub implements Parcelable {
private Message message;
private String messageType;
public static final String MESSAGE_TYPE_MESSAGE = "message";
public static final String MESSAGE_TYPE_CONNECT = "connect";

public Message getMessage() {
return message;
}

public void setMessage(Message message) {
this.message = message;
}

public String getMessageType() {
return messageType;
}

public void setMessageType(String messageType) {
this.messageType = messageType;
}

public MessageSub(Message message, String messageType) {
this.message = message;
this.messageType = messageType;
}

public MessageSub(Parcel parcel) {
messageType = parcel.readString();
switch (messageType) {
case MESSAGE_TYPE_CONNECT:
message = parcel.readParcelable(ConnectMessage.class.getClassLoader());
break;
default:
message = parcel.readParcelable(Message.class.getClassLoader());
break;
}
}

public final static Creator<MessageSub> CREATOR = new Creator<MessageSub>() {
@Override
public MessageSub createFromParcel(Parcel source) {
return new MessageSub(source);
}

@Override
public MessageSub[] newArray(int size) {
return new MessageSub[size];
}
};

@Override
public int describeContents() {
return 0;
}

@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(messageType);
dest.writeParcelable(message,flags);
}
}

3.2.2修改MessageManager.aidl文件。

　　将添加的信息修改为MessageSub。

package com.zhangmiao.aidlservice;

// Declare any non-default types here with import statements
import com.zhangmiao.aidlservice.MessageSub;
interface MessageManager {
List<MessageSub> getMessages();
void addMessage(in MessageSub message);
}

3.2.3.修改服务器端AIDL的onCreate()方法。

@Override
public void onCreate() {
super.onCreate();
Message message1 = new Message(1,"open");
MessageSub messageSub1 = new MessageSub(message1,MessageSub.MESSAGE_TYPE_MESSAGE);
mMessageList.add(messageSub1);
Message message2 = new Message(2,"get");
MessageSub messageSub2 = new MessageSub(message2,MessageSub.MESSAGE_TYPE_MESSAGE);
mMessageList.add(messageSub2);
Message connMessage = new ConnectMessage(3,"conn",1);
MessageSub messageSub3 = new MessageSub(connMessage,MessageSub.MESSAGE_TYPE_CONNECT);
mMessageList.add(messageSub3);
}

3.2.4.修改客户端的MainActivity的ServiceConnect对象的实现。

private ServiceConnection mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
Log.d(TAG,"ServiceConnection onServiceConnected");
MessageManager messageManager = MessageManager.Stub.asInterface(service);
try {
List<MessageSub> messages = messageManager.getMessages();
for(int i = 0;i<messages.size();i++){
String messageType = messages.get(i).getMessageType();
Message message = messages.get(i).getMessage();
switch (messageType){
case MessageSub.MESSAGE_TYPE_MESSAGE:
Log.d(TAG,"get Message for MessageManager:"+message.toString());
break;
case MessageSub.MESSAGE_TYPE_CONNECT:
ConnectMessage connectMessage = (ConnectMessage)message;
Log.d(TAG,"get conn Message for MessageManager:"+connectMessage.toString());
break;
default:
Log.d(TAG,"get Message for MessageManager:"+message.toString());
break;
}
}
}catch (RemoteException e){
e.printStackTrace();
}
}

@Override
public void onServiceDisconnected(ComponentName name) {
Log.d(TAG,"ServiceConnection onServiceDisconnected");
}
};

　　显示结果如下图：

4.AIDL使用的注意事项

4.1. 在接口中将序列化的数据类作为接口的参数时，需要添加in/out/inout，不然会如下错误：

Error:Execution failed for task ':aidlservice:compileDebugAidl'.
> java.lang.RuntimeException: com.android.ide.common.process.ProcessException:
　　Error while executing process D:\sdk\build-tools\25.0.2\aidl.exe with arguments {-pD:\sdk\platforms\android-25\framework.aidl -oD:\AndroidProgram\AIDLDemo\aidlservice\build\generated\source\aidl\debug -ID:\AndroidProgram\AIDLDemo\aidlservice\src\main\aidl
-ID:\AndroidProgram\AIDLDemo\aidlservice\src\debug\aidl -IC:\Users\JackMa\.android\build-cache\2e6503c935d0e7aae874a51ce291501bd59fa172\output\aidl -IC:\Users\JackMa\.android\build-cache\a228985c661fd225e06c74ab4fc1d2ba693ed5d6\output\aidl
-IC:\Users\JackMa\.android\build-cache\04bf36b1eaa6e79d64acf7cc2ed0353331a0adb5\output\aidl -IC:\Users\JackMa\.android\build-cache\0c304484ccb4b4195fb676627e57f7ba92b2bd5e\output\aidl -IC:\Users\JackMa\.android\build-cache\07915f8984a205b1822ca99eaa0be940f26c250e\output\aidl
-IC:\Users\JackMa\.android\build-cache\a3d0bacf6fdfaf349f8eda4b777bd602fa7e5c67\output\aidl
-IC:\Users\JackMa\.android\build-cache\1d232803c59995c7bfdd0a651a144487a3f5db22\output\aidl -IC:\Users\JackMa\.android\build-cache\e18e71aa63be1e08bcc427a44b82a10769bbf421\output\aidl
-IC:\Users\JackMa\.android\build-cache\4d089e6ce66be1802231fc929e45b8b592cfa5c5\output\aidl -IC:\Users\JackMa\.android\build-cache\57b6aa97fbde28ff421267076f032edb60508e5f\output\aidl
-dC:\Users\JackMa\AppData\Local\Temp\aidl4840819892296516909.d D:\AndroidProgram\AIDLDemo\aidlservice\src\main\aidl\com\zhangmiao\aidlservice\MessageManager.aidl}

　　In、out、inout指的是数据流通的方式，in与out分别表示客户端与服务器之间的两条单向的数据流向，inout则表示两端可双向流通数据。

4.2. 客户端与服务器端的aidl与aidl实现的java文件要保持一致，包名也要相同。

4.3.在类实现Parcelable的接口时，在writeToParcel()与构造函数参数为Parcel的两个方法中，调用parcel的写与读数据的顺序要一致。

参考文献：

http://www.open-open.com/lib/view/open1469493649028.html

http://www.open-open.com/lib/view/open1469494852171.html