Android进程通信IPC

IPC也看过很多次，每次看完后记会忘记，这次自己给它写下来加深印象

IPC

进程间通信(Inter-Process Communication),简称IPC,就是指进程与进程之间进行通信

基于Binder的AIDL和Messager的同一个应用的通信

步骤一

首先写个最基本的就是重写IBinder,增强服务端的的功能 看代码：

//IpcService.java文件
public class IpcService extends Service {
    private IBinder mIBinder;

    @Override
    public void onCreate() {
        super.onCreate();
        mIBinder = new MyBinder();
    }

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

    public class MyBinder extends Binder {
        public void print() {
            Log.d("PHN", "服务Service，执行任务");
        }
    }

}

注意要在清单文件中注册服务

public class MainActivity extends AppCompatActivity {

    private IpcService.MyBinder myBinder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //自动绑定服务
        Intent intent = new Intent(this, IpcService.class);
        MyServiceConnection serviceConnection = new MyServiceConnection();
        bindService(intent, serviceConnection, BIND_AUTO_CREATE);

        findViewById(R.id.bt).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (null != myBinder) {
                    myBinder.print();
                }
            }
        });
    }

    private class MyServiceConnection implements ServiceConnection {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            myBinder = (IpcService.MyBinder) service;
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    }
}

loginfo_01.png

执行点击服务端会打印信息，说明这个活动和服务进行通信是成功的！

步骤二

我们用Messager来做刚才的功能
1.首先在Service里面创建一个Hander用来接受消息：

private final static Handler mHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
       Log.d("PHN", "服务Service，执行任务");
    }
};

2.在Service里面创建一个Messager,并把Handler放入其中

private final static Messenger mMessenger = new Messenger(mHandler);

3.重写onbind方法,返回Messager里面的Binder

public IBinder onBind(Intent intent) {
    return mMessenger.getBinder();
}

贴出完整的服务代码

public class IpcService extends Service {

    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return mMessenger.getBinder();
    }


    private final static Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            Log.d("PHN", "服务Service，执行任务");
        }
    };
    private final static Messenger mMessenger = new Messenger(mHandler);

}

再贴出活动里的代码

public class MainActivity extends AppCompatActivity {

    private Messenger messenger;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //自动绑定服务
        Intent intent = new Intent(this, IpcService.class);
        MyServiceConnection serviceConnection = new MyServiceConnection();
        bindService(intent, serviceConnection, BIND_AUTO_CREATE);

        findViewById(R.id.bt).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (null != messenger) {
                    Message message = Message.obtain();
                    try {
                        messenger.send(message);
                    } catch (RemoteException e) {
                        e.printStackTrace();
                    }
                }
            }
        });
    }

    private class MyServiceConnection implements ServiceConnection {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            messenger = new Messenger(service);
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    }
}

执行看看结果

loginfo_02.png

果然可以得到同样的效果！

步骤三

上面我们可能看到只能是活动让服务执行任务，那么怎样才能让服务端让活动也执行任务呢，我们先对服务器端的代码进行修改,首先修改Service的Handler
看下面服务端代码处理：

public class IpcService extends Service {

    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return mMessenger.getBinder();
    }


    private final static Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            Log.d("PHN", "服务Service，执行任务");
            //获取Messager
            Messenger messenger = msg.replyTo;
            //创建消息
            Message msg_reply = Message.obtain();
            try {
                //发送
                messenger.send(msg_reply);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }
    };
    private final static Messenger mMessenger = new Messenger(mHandler);

}

接着我们在活动端也增加一个Handler和Messager来处理消息,贴出代码

public class MainActivity extends AppCompatActivity {

    private Messenger messenger;


    private final static Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            Log.d("PHN", "活动Acitivity，执行任务");
        }
    };
    private final static Messenger mReplyMessager = new Messenger(mHandler);


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //自动绑定服务
        Intent intent = new Intent(this, IpcService.class);
        MyServiceConnection serviceConnection = new MyServiceConnection();
        bindService(intent, serviceConnection, BIND_AUTO_CREATE);

        findViewById(R.id.bt).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (null != messenger) {
                    Message message = Message.obtain();
                    //通过msg把客户端的Messager传送到服务器端(关键代码)
                    message.replyTo =mReplyMessager;
                    try {
                        messenger.send(message);
                    } catch (RemoteException e) {
                        e.printStackTrace();
                    }
                }
            }
        });
    }

    private class MyServiceConnection implements ServiceConnection {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            messenger = new Messenger(service);
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    }
}

还有一个比较关键的地方,就是要在客户端发送消息的时候把客户端的Messager通过消息传送到服务器端
(msg.replyTo =mReplyMessager)

来执行看看结果：

loginfo_03.png

果然可以！！

步骤四

上面的通信是基于本应用里的，下面我们来看看不同的两个应用之间的通信AIDL，我是参照任玉刚的开发艺术里写例子，
1.首先那就是新建AIDL文件，很简单：

screenshot_01.png

那我就直接创建两个aidl文件Book.aidl,BookManager.aidl

screenshot_02.png

下面直接看文件的具体内容，我贴上来：

//Book.java
public class Book implements Parcelable{
    protected Book(Parcel in) {
        name = in.readString();
        price = in.readInt();
    }

    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];
        }
    };

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }

    private String name;

    private int price;

    public Book() {}

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

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(name);
        dest.writeInt(price);
    }
    /**
     * 参数是一个Parcel,用它来存储与传输数据
     * @param dest
     */
    public void readFromParcel(Parcel dest) {
        //注意，此处的读值顺序应当是和writeToParcel()方法中一致的
        name = dest.readString();
        price = dest.readInt();
    }

    @Override
    public String toString() {
        return "Book{" +
                "name='" + name + '\'' +
                ", price=" + price +
                '}';
    }
}

// Booka.aidl
package com.hanny.aidldemo;

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

// BookManager.aidl
package com.hanny.aidldemo;
import com.hanny.aidldemo.Book;
// Declare any non-default types here with import statements

interface BookManager {

    //所有的返回值前都不需要加任何东西，不管是什么数据类型
      List getBooks();

      //传参时除了Java基本类型以及String，CharSequence之外的类型
      //都需要在前面加上定向tag，具体加什么量需而定
      void addBook(in Book book);
}

文件搞好了，先编译下，看看会不会错,应该会错。

loginfo_03.png

这是因为把Book.java文件放到了aidl下，所以要在build.gradle 的android{ }的闭包下加入

   sourceSets {
        main {
            java.srcDirs = ['src/main/java', 'src/main/aidl']
        }
    }

不会错了，那就来写AIDL的service文件：

public class AIDLService extends Service {

    //包含Book对象的list
    private List mBooks = new ArrayList<>();
    private BookManager.Stub bookManager = new BookManager.Stub() {
        @Override
        public List getBooks() throws RemoteException {
            if (mBooks != null) {
                return mBooks;
            }
            return new ArrayList();
        }

        @Override
        public void addBook(Book book) throws RemoteException {
            synchronized (this) {
                if (mBooks == null) {
                    mBooks = new ArrayList();
                }
                if (book == null) {
                    book = new Book();
                }
                book.setPrice(23);
                if (!mBooks.contains(book)) {
                    mBooks.add(book);
                }
                //打印mBooks列表，观察客户端传过来的值
                Log.e("PHN", "增加后的图书 : " + mBooks.toString());
            }
        }
    };

    @Override
    public void onCreate() {
        super.onCreate();
        Book book = new Book();
        book.setName("Android开发艺术探索");
        book.setPrice(28);
        mBooks.add(book);
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {

        return bookManager;
    }
}

服务端写好了，那就新建一个工程，然后把服务端的aidl下的文件全部拷贝过来~放在main下级目录！

screenshot_03.png

接着在活动里用隐式意图开启服务！这样的话就要在服务端的清单文件里给服务配上action

   <service android:name=".AIDLService">
            <intent-filter>
                <action android:name="action.ipc"/>
            </intent-filter>
        </service>

看看客户端活动里的代码：

public class MainActivity extends AppCompatActivity {

    //标志当前与服务端连接状况的布尔值，false为未连接，true为连接中
    private boolean mBound = false;
    private BookManager bookManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findViewById(R.id.bt_get).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                addBook();
            }
        });
    }

    private void addBook() {
        if (!mBound) {
            attemptToBindService();
            Toast.makeText(this, "当前与服务端处于未连接状态，正在尝试重连，请稍后再试", Toast.LENGTH_SHORT).show();
            return;
        }
        if (bookManager == null) return;

        Book book = new Book();
        book.setName("APP研发录In");
        book.setPrice(30);
        try {
            bookManager.addBook(book);
            Log.e(getLocalClassName(), book.toString());
        } catch (RemoteException e) {
            e.printStackTrace();
        }
    }

    //开启服务
    private void attemptToBindService() {
        Intent intent = new Intent();
        intent.setAction("action.ipc");
        intent.setPackage("com.hanny.aidldemo");
        bindService(intent, mServiceConnection, BIND_AUTO_CREATE);
    }

    private ServiceConnection mServiceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            bookManager = BookManager.Stub.asInterface(service);
            mBound = true;
            if (bookManager != null) {
                try {
                    List books = bookManager.getBooks();
                    Log.d("PHN", "初始化得到的书: "+books.toString());
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            mBound = false;
        }
    };


    @Override
    protected void onStop() {
        super.onStop();
        if (mBound) {
            unbindService(mServiceConnection);
            mBound = false;
        }
    }

}

下面先运行服务端apk ，然后运行客服务apk然后点击增加图书，看看客户端和服务端的打印结果：

Paste_Image.png

反正就是这么简单，动手实践加深印象，并没有什么难的地方，

注意地方

AIDL 发生异常的原因 Android java.lang.SecurityException: Binder invocation to an incorrect interface

解决方法如下：
在使用上请注意，服务端与客户端都要有相同的接口（使用到的），这里的“相同”是指完全相同，包括包名，也就是说要在不同工程下建立相同的包名，这样一来，问题应该迎刃而解了！