使用AIDL实现Android的跨进程通信

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AIDL

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Android

AIDL(Android Interface Definition Language), 即Android接口定义语言. 在Android中, AIDL是跨进程通信的主要实现方式. 我们同样也可以使用AIDL, 实现自己的跨进程方案. 本文介绍AIDL的使用方式.

服务端: 创建Service服务监听客户端的请求, 实现AIDL接口.

客户端: 绑定服务端, 调用AIDL的方法.

AIDL接口: 跨进程通信的接口, AIDL的包名需要与项目的包名相同, 默认生成即可.

AIDL支持的数据类型: 基本类型, 字符串类型(String&CharSequence), List, Map, Parcelable, AIDL接口. 共六种.

流程: 客户端注册服务端, 服务端添加新书, 客户端接收, 并提供客户端的查询书数量的接口.

本文源码的GitHub下载地址

AIDL

本文使用自定义的数据类型Book类, 实现Parcelable接口, 具体参考.

public class Book implements Parcelable {    public int bookId;    public String bookName;    public Book(int bookId, String bookName) {        this.bookId = bookId;        this.bookName = bookName;    }    @Override public int describeContents() {        return 0;    }    @Override public void writeToParcel(Parcel dest, int flags) {        dest.writeInt(bookId);        dest.writeString(bookName);    }    public static final Parcelable.Creator CREATOR = new Parcelable.Creator() {        @Override public Book createFromParcel(Parcel source) {            return new Book(source);        }        @Override public Book[] newArray(int size) {            return new Book[size];        }    };    private Book(Parcel source) {        bookId = source.readInt();        bookName = source.readString();    }    @Override public String toString() {        return "ID: " + bookId + ", BookName: " + bookName;    }}

AIDL使用自定义类, 需要声明Parcelable类.

// IBook.aidlpackage org.wangchenlong.wcl_aidl_demo;// Declare any non-default types here with import statementsparcelable Book;

添加AIDL的接口, 用于通知新书到达.

// IOnNewBookArrivedListener.aidlpackage org.wangchenlong.wcl_aidl_demo;// Declare any non-default types here with import statementsimport org.wangchenlong.wcl_aidl_demo.Book;interface IOnNewBookArrivedListener {    /**     * 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);    void onNewBookArrived(in Book newBook);}

AIDL文件注释较多, 都是自动生成, 不影响阅读.

核心AIDL类, 书籍管理器, 四个方法, 获取图书列表, 添加书籍, 注册接口, 解注册接口. 注意, 使用其他方法, 需要import导入相应文件.

// IBookManager.aidlpackage org.wangchenlong.wcl_aidl_demo;// Declare any non-default types here with import statementsimport org.wangchenlong.wcl_aidl_demo.Book;import org.wangchenlong.wcl_aidl_demo.IOnNewBookArrivedListener;interface IBookManager {    /**     * 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);    List getBookList(); // 返回书籍列表    void addBook(in Book book); // 添加书籍    void registerListener(IOnNewBookArrivedListener listener); // 注册接口    void unregisterListener(IOnNewBookArrivedListener listener); // 注册接口}

所有的参数都需要标注参数方向, in表示输入类型, out表示输出类型, inout表示输入输出类型. out与inout的开销较大, 不能统一使用高级方向.

服务端

服务端通过Binder实现AIDL的IBookManager.Stub接口.

private Binder mBinder = new IBookManager.Stub() {    @Override public List getBookList() throws RemoteException {        SystemClock.sleep(5000); // 延迟加载        return mBookList;    }    @Override public void addBook(Book book) throws RemoteException {        mBookList.add(book);    }    @Override    public void registerListener(IOnNewBookArrivedListener listener) throws RemoteException {        mListenerList.register(listener);        int num = mListenerList.beginBroadcast();        mListenerList.finishBroadcast();        Log.e(TAG, "添加完成, 注册接口数: " + num);    }    @Override    public void unregisterListener(IOnNewBookArrivedListener listener) throws RemoteException {        mListenerList.unregister(listener);        int num = mListenerList.beginBroadcast();        mListenerList.finishBroadcast();        Log.e(TAG, "删除完成, 注册接口数: " + num);    }};

服务启动时, 添加两本新书, 并使用线程继续添加.

@Override public void onCreate() {    super.onCreate();    mBookList.add(new Book(1, "Android"));    mBookList.add(new Book(2, "iOS"));    new Thread(new ServiceWorker()).start();}

添加书籍, 并发送通知.

private class ServiceWorker implements Runnable {    @Override public void run() {        while (!mIsServiceDestroyed.get()) {            try {                Thread.sleep(5000);            } catch (InterruptedException e) {                e.printStackTrace();            }            num++;            if (num == 5) {                mIsServiceDestroyed.set(true);            }            Message msg = new Message();            mHandler.sendMessage(msg); // 向Handler发送消息,更新UI        }    }}private Handler mHandler = new Handler() {    public void handleMessage(Message msg) {        int bookId = 1 + mBookList.size();        Book newBook = new Book(bookId, "新书#" + bookId);        try {            onNewBookArrived(newBook);        } catch (RemoteException e) {            e.printStackTrace();        }    }};

向注册监听的, 发送新书的添加通知.

private void onNewBookArrived(Book book) throws RemoteException {    mBookList.add(book);    Log.e(TAG, "发送通知的数量: " + mBookList.size());    int num = mListenerList.beginBroadcast();    for (int i = 0; i < num; ++i) {        IOnNewBookArrivedListener listener = mListenerList.getBroadcastItem(i);        Log.e(TAG, "发送通知: " + listener.toString());        listener.onNewBookArrived(book);    }    mListenerList.finishBroadcast();}

在AndroidManifest中, Service与Activity不在同一进程.

客户端

绑定服务和解绑服务, 绑定服务的具体内容, 都是在mConnection中实现.

@Overrideprotected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    mTextView = (TextView) findViewById(R.id.main_tv_book_list);}@Override protected void onDestroy() {    if (mRemoteBookManager != null && mRemoteBookManager.asBinder().isBinderAlive()) {        try {            Log.e(TAG, "解除注册");            mRemoteBookManager.unregisterListener(mOnNewBookArrivedListener);        } catch (RemoteException e) {            e.printStackTrace();        }    }    unbindService(mConnection);    super.onDestroy();}

添加内容, 注册监听接口.

private ServiceConnection mConnection = new ServiceConnection() {    @Override public void onServiceConnected(ComponentName name, IBinder service) {        IBookManager bookManager = IBookManager.Stub.asInterface(service);        try {            mRemoteBookManager = bookManager;            Book newBook = new Book(3, "学姐的故事");            bookManager.addBook(newBook);            new BookListAsyncTask().execute();            bookManager.registerListener(mOnNewBookArrivedListener);        } catch (RemoteException e) {            e.printStackTrace();        }    }    @Override public void onServiceDisconnected(ComponentName name) {        mRemoteBookManager = null;        Log.e(TAG, "绑定结束");    }};

当调用监听接口时, 异步显示图书列表.

private IOnNewBookArrivedListener mOnNewBookArrivedListener = new IOnNewBookArrivedListener.Stub() {    @Override public void onNewBookArrived(Book newBook) throws RemoteException {        mHandler.obtainMessage(MESSAGE_NEW_BOOK_ARRIVED, newBook).sendToTarget();    }};private Handler mHandler = new Handler() {    @Override public void handleMessage(Message msg) {        switch (msg.what) {            case MESSAGE_NEW_BOOK_ARRIVED:                Log.e(TAG, "收到的新书: " + msg.obj);                new BookListAsyncTask().execute();                break;            default:                super.handleMessage(msg);                break;        }    }};

点击绑定服务按钮, 执行绑定服务. 点击获取图书数量按钮, 获取当前列表的数量.

效果

Android跨进程通信比较复杂, 但是意义重大, 目前常用的动态加载框架都需要处理跨进程通信等问题, 熟练基本原理, 掌握使用方式.

OK, that's all! Enjoy it!

AIDL

服务端

客户端

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