欢迎访问移动开发之家(rcyd.net),关注移动开发教程。移动开发之家  移动开发问答|  每日更新

AIDL使用解析,aidl解析

来源: 开发者 投稿于  被查看 23267 次 评论:122

AIDL使用解析,aidl解析


简书本文地址:点击跳转到简书查看

 

 

 

之前面试的时候被问到这个问题,然而当时只有一个大致的印象,随GG,于是我就重新整理的一下。这里大力推荐《Android开发艺术探索》这本书,写的太好了!

1.AIDL

AIDL(Android Interface Define Language) 是IPC进程间通信方式的一种.用于生成可以在Android设备上两个进程之间进行进程间通信(interprocess communication, IPC)的代码.

2.AIDL和Messenger的区别:

3.使用AIDL的步骤:

下面一个简单的例子来说明AIDL的使用:假设一个情景我们需要计算a+b,我们需要在客户端传递两个参数a和b,然后将参数传递给服务端(另一个进程)来进行计算,计算结果传递给客户端。

目录结构

1. 新建一个项目作为服务端,在项目中新建AIDL文件。这里我命名为:IImoocAIDL.aidl

// IImoocAIDL.aidl
package com.mecury.aidltest;
// Declare any non-default types here with import statements
interface IImoocAIDL {    
    //计算num1 + num2    
    int add(int num1,int num2);
}

点击同步按钮(一定要先同步),查看是否生成IImoocAIDL文件。

aidl的生成.gif


生成的文件如下,我写了详细的注释,相信你能够看懂:

生成的AIDL文件#IImoocAIDL.java:

这里来说一下AIDL通信的原理:首 先看这个文件有一个叫做proxy的类,这是一个代理类,这个类运行在客户端中,其实AIDL实现的进程间的通信并不是直接的通信,客户端和服务端都是通 过proxy来进行通信的:客户端调用的方法实际是调用是proxy中的方法,然后proxy通过和服务端通信将返回的结果返回给客户端。


package com.mecury.aidltest;


public interface IImoocAIDL extends android.os.IInterface {
    
    public static abstract class Stub extends android.os.Binder implements com.mecury.aidltest.IImoocAIDL {
        private static final java.lang.String DESCRIPTOR = "com.mecury.aidltest.IImoocAIDL"; 

        
        public Stub() {
            this.attachInterface(this, DESCRIPTOR);
        }

        
        
        
        public static com.mecury.aidltest.IImoocAIDL asInterface(android.os.IBinder obj) {
            if ((obj == null)) {
                return null;
            }
            android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
            if (((iin != null) && (iin instanceof com.mecury.aidltest.IImoocAIDL))) {
                return ((com.mecury.aidltest.IImoocAIDL) iin);
            }
            return new com.mecury.aidltest.IImoocAIDL.Stub.Proxy(obj);
        }
        
        @Override
        public android.os.IBinder asBinder() {
            return this;
        }

        
        @Override
        public boolean onTransact(int code, android.os.Parcel data, android.os.Parcel reply, int flags) throws android.os.RemoteException {
            switch (code) {
                case INTERFACE_TRANSACTION: {
                    reply.writeString(DESCRIPTOR);
                    return true;
                }
                case TRANSACTION_add: {
                    data.enforceInterface(DESCRIPTOR);
                    
                    int _arg0;
                    _arg0 = data.readInt();
                    int _arg1;
                    _arg1 = data.readInt();
                    
                    int _result = this.add(_arg0, _arg1);
                    
                    reply.writeNoException();
                    reply.writeInt(_result);
                    return true;
                }
            }
            return super.onTransact(code, data, reply, flags); 
        }

        
        private static class Proxy implements com.mecury.aidltest.IImoocAIDL {
            private android.os.IBinder mRemote; 

            Proxy(android.os.IBinder remote) {
                mRemote = remote;
            }
            
            @Override
            public android.os.IBinder asBinder() {
                return mRemote;
            } 

            public java.lang.String getInterfaceDescriptor() {
                return DESCRIPTOR;
            }

            
            @Override
            public int add(int num1, int num2) throws android.os.RemoteException {
                android.os.Parcel _data = android.os.Parcel.obtain();
                android.os.Parcel _reply = android.os.Parcel.obtain();
                int _result;
                try {
                    
                    _data.writeInterfaceToken(DESCRIPTOR);
                    _data.writeInt(num1);
                    _data.writeInt(num2);
                    
                    mRemote.transact(Stub.TRANSACTION_add, _data, _reply, 0);
                    _reply.readException();
                    _result = _reply.readInt();
                } finally {
                    _reply.recycle();
                    _data.recycle();
                }
                return _result;
            }
        }
        
        static final int TRANSACTION_add = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
    }

    
    public int add(int num1, int num2) throws android.os.RemoteException;
}

代码中的几个方法:
DESCRIPTION
Binderd的唯一标识,一般用当前的类名表示。
asInterface(android.os.IBinder obj)
用于将服务端的Binder对象转换为客户端需要的AIDL接口类型的对象,转换区分进程,客户端服务端位于同一进程,返回服务端的 //Stub对象本身;否则返回的是系统的封装后的Stub.proxy对象。
asBInder
返回Binder对象
onTransact
此方法运行在服务端中的Binder线程池中,当客户端发起跨进程请求时,远程请求会通过系统底层封装后交由此方法处理。
Proxy#add
此 方法运行在客户端,当客户端远程调用此方法时,它的内部实现是这样的:首先创建该方法所需要的输入型Parcel对象_data、输出型Parcel对象 _reple和返回值对象_result,然后将该方法的参数信息写入_data中;接着调用transact方法来发RPC请求,同时当前线程挂起;然 后服务端的onTransact方法会被调用,直到RPC过程返回后,当前线程继续执行,并从_reply中取出RPC过程返回的结果,写入 _result中。

2.新建一个客户端File-》new--》new module--》phone & table module。这里我的命名为aidlclient.java
同样要在客户端创建AIDL文件,里面的包名和所在位置要求完全一样。

3.在服务端创建一个Service用来监听客户端的连接请求。

public class IRemoteService extends Service {

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

    private IBinder iBinder = new IImoocAIDL.Stub(){

        @Override
        public int add(int num1, int num2) throws RemoteException {
            Log.e("TAG","收到了来自客户端的请求" + num1 + "+" + num2 );
            return num1 + num2;
        }
    };
}

最后,别忘记在AndroidManifest.xml中注册该Service。

<service android:name=".IRemoteService"
            android:process=":remote"
            android:exported="true">
            <intent-filter>
                <action android:name="com.mecury.aidltest.IRomoteService"/>
            </intent-filter>
</service>

4.客户端的编写
activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <EditText
        android:id="@+id/num1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="+"/>
    <EditText
        android:id="@+id/num2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="="/>
    <TextView
        android:id="@+id/text"
        android:layout_width="match_parent"
        android:layout_height="30dp" />
    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="计算"/>
</LinearLayout>

MainActivity.java

package com.mecury.aidlclient;

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.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.mecury.aidltest.IImoocAIDL;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText num1;
    private EditText num2;
    private Button button;
    private TextView text;

    private IImoocAIDL iImoocAIDL;

    private ServiceConnection conn = new ServiceConnection() {

        
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            iImoocAIDL = IImoocAIDL.Stub.asInterface(service);
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            iImoocAIDL = null;
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        bindService();
        initView();

    }

    private void initView() {
        num1 = (EditText) findViewById(R.id.num1);
        num2 = (EditText) findViewById(R.id.num2);
        button = (Button) findViewById(R.id.button);
        text = (TextView) findViewById(R.id.text);

        button.setOnClickListener(this);
    }


    @Override
    public void onClick(View v) {
        int num11 = Integer.parseInt(num1.getText().toString());
        int num22 = Integer.parseInt(num2.getText().toString());

        try {
            int res = iImoocAIDL.add(num11,num22);
            text.setText(num11 +"+"+ num22 +"="+ res);
        } catch (RemoteException e) {
            e.printStackTrace();
        }
    }

    private void bindService() {

        Intent intent = new Intent();
        
        intent.setAction("com.mecury.aidltest.IRomoteService");
        
        intent.setComponent(new ComponentName("com.mecury.aidltest","com.mecury.aidltest.IRemoteService"));
        
        bindService(intent,conn, Context.BIND_AUTO_CREATE);
    }

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

5.运行代码
先启动服务端,在启动客户端。

结果.gif

小结:看完上面,是不是已经对于AIDL的用法有个大概的了解。下面来看一个更为复杂的例子,这是《android开发艺术探索》中的例子: 建立一个图书管理,能够添加图书、得到图书列表、使用观察者模式、当新书到达时通知所有观察者。

4.AIDL高级示例

1.先看Book.java。需要注意的是,AIDL能够传输的数据类型有限制,这里必须将book序列化才能够使用,同时Book类在客户端和服务端都要这样定义

Book.java
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);
    }

    protected Book(Parcel in) {
        bookId = in.readInt();
        bookName = in.readString();
    }

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

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

    @Override
    public String toString() {
        return bookId + ":" + bookName;
    }
}

2.AIDL文件

Book.aidl
package com.mecury.aidltest2;
parcelable Book;
IOnNewBookArrivedListener.aidl
package com.mecury.aidltest2;

import com.mecury.aidltest2.book;
interface IOnNewBookArrivedListener {
     void OnNewBookArrivedListener(in Book book);
}
IBookManager.aidl
package com.mecury.aidltest2;

import com.mecury.aidltest2.book;
import com.mecury.aidltest2.IOnNewBookArrivedListener;

interface IBookManager {
    List<Book> getBookList();
    void addBook(in Book book);
    void registerListener(IOnNewBookArrivedListener listener);
    void unregisterListener(IOnNewBookArrivedListener listener);
}

3.服务端

BookManagerService.java
public class BookManagerService extends Service {

    private static final String TAG = "BMS";

    private AtomicBoolean mIsServiceDestoryed = new AtomicBoolean(false);
    private CopyOnWriteArrayList<Book> mBookList = new CopyOnWriteArrayList<Book>();
    private RemoteCallbackList<IOnNewBookArrivedListener> mListeners = new RemoteCallbackList<>();

    
    private Binder mBinder = new IBookManager.Stub(){

        @Override
        public List<Book> getBookList() throws RemoteException {
            return mBookList;
        }

        @Override
        public void addBook(Book book) throws RemoteException {
            mBookList.add(book);
        }

        @Override
        public void registerListener(IOnNewBookArrivedListener listener) throws RemoteException {
            mListeners.register(listener);
        }

        @Override
        public void unregisterListener(IOnNewBookArrivedListener listener) throws RemoteException {
            mListeners.unregister(listener);
        }
    };

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

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }
    
    private void onNewBookArrived(Book book) throws RemoteException {
        mBookList.add(book);
        final int N = mListeners.beginBroadcast();
        Log.e("onNewBookArrived","registener listener size:" + N);
        for (int i = 0; i < N; i++){
            IOnNewBookArrivedListener l = mListeners.getBroadcastItem(i);
            if (l!=null){
                l.OnNewBookArrivedListener(book);
            }
        }
        mListeners.finishBroadcast();
    }
    
    private class serviceWork implements Runnable{

        @Override
        public void run() {
            while (!mIsServiceDestoryed.get()){
                try {
                    Thread.sleep(5000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                int bookId = mBookList.size() + 1;
                Book newBook = new Book(bookId,"new Book #" + bookId);

                try {
                    onNewBookArrived(newBook);
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    @Override
    public void onDestroy() {
        mIsServiceDestoryed.set(true);
        super.onDestroy();
    }
}
在里面我们发现几处特殊的地方
1.CopyOnWriteArrayList:支持并发的读写,这里我们使用它来进行自动的线程同步
2.RemoteCallBackList:是系统专门提供的用于删除跨进程listener的接口。它的工作原理其实很简单:在它的内部有一个Map结构专门用来保存所有AIDL回调ArrayMap<IBinder, Callback> mCallback = new ArrayMap<IBinder, Callback>();,当客户端注册listener时,会把listener的信息注册到mCallBack中,其中key和value通过下面方式获得:IBinder key = listener.asBinder();Callback value = new Callback(listener, cookie)。另外一点我们需要知道:对 象是不能跨进程传输的,对象的跨进程传输过程实际是反序列化的过程,这是我们Book类为什么要实现Parcelable接口的原因。在跨进程传输 中,Binder会把客户端传递的对象重新转化并生成另一对象,当我们注册和解注册的过程中使用的是同一个客户端对象,但是通过Binder传递到服务端 却生成了两个不同的对象。而RemoteCallBackList就是用来解决这个问题的,虽然所多次跨进程传输客户端的同一个对象会在服务端 生成不同的对象,但在这些新生成的对象都有一个共同点,那就是他们底层的Binder对象是同一个,利用这个,就可以实现上面无法实现的功能。当客户端解 注册时,我们只要遍历所有的listener,找出那个和解注册listener具有相同Binder对象服务器listener并把他删除掉即可,这就 是RemoteCallbackList为我们做的事情。(对于这个看不明白的,可以看看《android 开发艺术探索》)

4.客户端:

MainActivity.java
public class MainActivity extends AppCompatActivity {

    private static final String TAG = "BookManagerActivity";
    private IBookManager bookManager;
    private static final int MESSAGE_NEW_BOOK_ARRIVED = 1;

    private Handler mHandler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case MESSAGE_NEW_BOOK_ARRIVED:
                    Log.e(TAG, "received new book:" + msg.obj);
                    break;
                default:
                    super.handleMessage(msg);
            }

        }
    };

    private ServiceConnection mService = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            bookManager = IBookManager.Stub.asInterface(service);
            try {
                List<Book> list = bookManager.getBookList();
                Log.e(TAG, "query book list,list type:" + list.getClass().getCanonicalName());
                Log.e(TAG, "query book list:" + list.toString());
                Book newBook = new Book(3, "android进阶");
                bookManager.addBook(newBook);
                Log.e(TAG, "add book:" + newBook);
                List<Book> newList =  bookManager.getBookList();
                Log.e(TAG, "query book list:" + newList.toString());
                bookManager.registerListener(mNewBookArrivedListener);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            bookManager = null;
            Log.e(TAG, "binder died.");
        }
    };

    private IOnNewBookArrivedListener mNewBookArrivedListener = new IOnNewBookArrivedListener.Stub() {
        @Override
        public void OnNewBookArrivedListener(Book book) throws RemoteException {
            mHandler.obtainMessage(MESSAGE_NEW_BOOK_ARRIVED, book).sendToTarget();
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        bindService();

    }

    private void bindService() {
        Intent intent = new Intent();
        intent.setAction("com.mecury.aidltest2.BookManagerService");
        intent.setComponent(new ComponentName("com.mecury.aidltest2", "com.mecury.aidltest2.BookManagerService"));
        bindService(intent, mService, Context.BIND_AUTO_CREATE);
    }

    @Override
    protected void onDestroy() {
        if (bookManager != null && bookManager.asBinder().isBinderAlive()){
            Log.e(TAG, "unregister listener:" + mNewBookArrivedListener);
            try {
                bookManager.unregisterListener(mNewBookArrivedListener);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }
        unbindService(mService);
        super.onDestroy();
    }
}

目录结构:


目录

运行结果:

客户端log:

06-29 22:52:29.438 17007-17007/com.mecury.client E/BookManagerActivity: query book list,list type:java.util.ArrayList
06-29 22:52:29.438 17007-17007/com.mecury.client E/BookManagerActivity: query book list:[1:Android, 2:Ios]
06-29 22:52:29.439 17007-17007/com.mecury.client E/BookManagerActivity: add book:3:android进阶
06-29 22:52:29.439 17007-17007/com.mecury.client E/BookManagerActivity: query book list:[1:Android, 2:Ios, 3:android进阶]
06-29 22:52:33.487 17007-17007/com.mecury.client E/BookManagerActivity: received new book:4:new Book #4
06-29 22:52:38.489 17007-17007/com.mecury.client E/BookManagerActivity: received new book:5:new Book #5
06-29 22:52:43.491 17007-17007/com.mecury.client E/BookManagerActivity: received new book:6:new Book #6
06-29 22:52:48.503 17007-17007/com.mecury.client E/BookManagerActivity: received new book:7:new Book #7

服务端log:

06-29 22:52:33.487 17027-17044/com.mecury.aidltest2:remote E/onNewBookArrived: registener listener size:1
06-29 22:52:38.488 17027-17044/com.mecury.aidltest2:remote E/onNewBookArrived: registener listener size:1
06-29 22:52:43.490 17027-17044/com.mecury.aidltest2:remote E/onNewBookArrived: registener listener size:1
06-29 22:52:48.492 17027-17044/com.mecury.aidltest2:remote E/onNewBookArrived: registener listener size:1

5.一些补充

AIDL支持的数据类型
  • 基本数据类型(int、long、char 等)
  • String 和 CharSequence
  • List:只支持ArrayList,里面的每个元素都必须被AIDL支持。
  • Map: 只支持HashMap, 里面的每个元素都必须被AIDL支持。
  • Parcelable: 所有实现了Parcelable接口的对象
  • AIDL: 所有的AIDL接口本身也可以在AIDL文件中使用

参考:
1.《android开发艺术探索》

 

用户评论