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