什么是IPC

Inter-Process Comminication 進(jìn)程間通信

各平臺(tái)進(jìn)程間如何通信

• Windows
  剪切板肛搬、管道和油槽
• Linux
  命名管道囚似、共享內(nèi)容和信號(hào)量
• Android
  基于Linux，常用Binder和Socket

Android應(yīng)用如何開(kāi)啟多進(jìn)程

• 通過(guò)給四大組件指定android:process
• 通過(guò)JNI在native層fork一個(gè)新的進(jìn)程 不推薦

指定android:processs

• 系統(tǒng)將為每個(gè)進(jìn)程名生成一個(gè)進(jìn)程，進(jìn)程名相同將運(yùn)行在同一進(jìn)程中

同程序多進(jìn)程的危害

對(duì)象序列化

• Serializable : 常用于存儲(chǔ)和網(wǎng)絡(luò)通信
• Parcelable ： 常用于內(nèi)存通信屈嗤，由于在內(nèi)存中序列化，效率更高
• Bundle

ipc方式的優(yōu)缺點(diǎn)和適用場(chǎng)景

Binder各角度理解

• IPC 是一種跨進(jìn)程通信方式埋泵，也可理解為虛擬的物理設(shè)備/dev/binder
• Android Framework 是ServiceManager連接各種Mangager的橋梁
• 應(yīng)用層 是客戶端和服務(wù)端進(jìn)行通信的媒介AIDL

AIDL使用解析

文件共享

• 適合在數(shù)據(jù)同步要求不高的進(jìn)程之間進(jìn)行通信
• SharedPreference也是文件共享幔欧，但由于Android對(duì)他有一層內(nèi)存緩存，所以多進(jìn)程操作很容易丟失數(shù)據(jù)丽声。

使用Messenger

• 是輕量級(jí)IPC方案礁蔗，頂層使用AIDL實(shí)現(xiàn)
• 串行(Handler)處理請(qǐng)求，大量并發(fā)請(qǐng)求狀況不適用

public class MessengerService extends Service {
    private static class MessengerHandler extends Handler {
        @Override
        public void handleMessage(Message msg) {
            //  回?cái)?shù)據(jù)
            switch (msg.what) {
                case 0:
                    System.out.println(msg.getData().getString("request"));
                    Messenger client = msg.replyTo;
                    Message replyMsg = Message.obtain(null, 1);
                    Bundle data = new Bundle();
                    data.putString("result", "i've received you request");
                    replyMsg.setData(data);
                    try {
                        client.send(replyMsg);
                        break;
                    } catch (RemoteException e) {
                        e.printStackTrace();
                    }
                default:
                    super.handleMessage(msg);
            }
        }
    }

    private final Messenger mMessenger = new Messenger(new MessengerHandler());

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

<service android:name=".MessengerService"
  android:process=":remote"/>

public class MainActivity extends AppCompatActivity {
    private Messenger mMessenger;

    private Messenger mGetReplyMessenger = new Messenger(new ClientMsgHandler());

    private ServiceConnection mServiceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            //  發(fā)數(shù)據(jù)
            mMessenger = new Messenger(service);
            Message msg = Message.obtain(null, 0);
            Bundle data = new Bundle();
            data.putString("request", "i'm client, send a msg");
            msg.setData(data);
            msg.replyTo = mGetReplyMessenger;
            try {
                mMessenger.send(msg);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }

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

    static class ClientMsgHandler extends Handler {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case 1:
                    Bundle data = msg.getData();
                    System.out.println(data.getString("result"));
                    break;
                default:
                    super.handleMessage(msg);
            }
        }
    }

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

        Intent intent = new Intent(MainActivity.this, MessengerService.class);
        bindService(intent, mServiceConnection, Context.BIND_AUTO_CREATE);
    }

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

AIDL跨進(jìn)程回調(diào)

• 封裝一個(gè)集合存儲(chǔ)回調(diào)

• 由于跨進(jìn)程對(duì)象會(huì)經(jīng)過(guò)序列化和反序列化（普通集合移除時(shí)傳入對(duì)象和集合中對(duì)象不同）雁社，所以需要使用RemoteCallbackList來(lái)避免回調(diào)對(duì)象移除失敗

• RemoteCallbackList : 內(nèi)部有個(gè)ArrayMap結(jié)構(gòu)專門(mén)用來(lái)保存AIDL回調(diào)浴井，這個(gè)Map的key是Ibinder類型，value是CallBack類型霉撵。其中CallBack中封裝了真正的Listener遠(yuǎn)程對(duì)象

• 服務(wù)端

// IOnChangeListener.aidl  回調(diào)接口
package com.rtfsc.passwordinputview;
interface IOnChangeListener {
    void onChange(String aString);
}

// IMyAidlInterface.aidl 遠(yuǎn)程服務(wù)接口
package com.rtfsc.passwordinputview;
import com.rtfsc.passwordinputview.IOnChangeListener;
interface IMyAidlInterface {
    void doSomething(String str);
    void registerListener(IOnChangeListener listener);
    void unregisterListener(IOnChangeListener listener);
}

// AidlService.java 遠(yuǎn)程服務(wù)Service
public class AidlService extends Service {
    private RemoteCallbackList<IOnChangeListener> mCallbackList = new RemoteCallbackList<>();

    private Binder mBinder = new IMyAidlInterface.Stub() {

        @Override
        public void doSomething(String str) throws RemoteException {
            System.out.println("AidlService.doSomething@" + str);
        }

        @Override
        public void registerListener(IOnChangeListener listener) throws RemoteException {
            listener.onChange("call back register");
            System.out.println("AidlService.registerListener@" + mCallbackList.register(listener));

        }

        @Override
        public void unregisterListener(IOnChangeListener listener) throws RemoteException {
            listener.onChange("call back unregister");
            System.out.println("AidlService.unregisterListener@" + mCallbackList.unregister(listener));
        }
    };

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

// AndroidManifest.xml
<service    
  android:name=".AidlService"    
  android:process=":remote"/>

• 客戶端

public class MainActivity extends AppCompatActivity {
    IMyAidlInterface iMyAidlInterface;
    private ServiceConnection mServiceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            iMyAidlInterface = IMyAidlInterface.Stub.asInterface(service);
            try {
                iMyAidlInterface.registerListener(mListener);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };

    private IOnChangeListener mListener = new IOnChangeListener.Stub() {
        @Override
        public void onChange(String aString) throws RemoteException {
            System.out.println(aString);
        }
    };

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

        Intent intent = new Intent(MainActivity.this, AidlService.class);
        bindService(intent, mServiceConnection, Context.BIND_AUTO_CREATE);
    }

    @Override
    protected void onDestroy() {
        try {
            if (iMyAidlInterface != null) {
                iMyAidlInterface.unregisterListener(mListener);
            }
        } catch (RemoteException e) {
            e.printStackTrace();
        }
        unbindService(mServiceConnection);
        super.onDestroy();
    }
}

• Log

07-28 18:04:24.017 6844-6844/com.rtfsc.passwordinputview I/System.out: call back register
07-28 18:04:24.017 6873-6890/com.rtfsc.passwordinputview:remote I/System.out: AidlService.registerListener@true
07-28 18:04:29.027 6844-6844/com.rtfsc.passwordinputview I/System.out: call back unregister
07-28 18:04:29.027 6873-6890/com.rtfsc.passwordinputview:remote I/System.out: AidlService.unregisterListener@true