IPC机制（一）

一、概念

public class PicEntity implements Parcelable {    public String picURL;    public String middlePicURL;    public String smallPicURL;    //从序列化后得对象中创建原始对象    protected PicEntity(Parcel in) {        picURL = in.readString();        middlePicURL = in.readString();        smallPicURL = in.readString();    }    //反序列化的过程    public static final Creator<PicEntity> CREATOR = new Creator<PicEntity>() {        //从序列化后的对象返回原始对象        @Override        public PicEntity createFromParcel(Parcel in) {            return new PicEntity(in);        }        //创建指定长度的原始对象数组        @Override        public PicEntity[] newArray(int size) {            return new PicEntity[size];        }    };    //返回当前对象的内容描述    @Override    public int describeContents() {        return 0;    }    //序列化的过程    @Override    public void writeToParcel(Parcel dest, int flags) {        dest.writeString(picURL);        dest.writeString(middlePicURL);        dest.writeString(smallPicURL);    }}Intent、Bundle、Bitmap都是直接序列化的。List和Map也可序列化，里面的每个元素都是可序列化的。3、区别Serializable 是java序列化接口，将整个对象序列化，简单开销大，序列化和反序列化需要大量I/O操作。Parcelable是Android序列化方式，适合Android平台。将对象的每个部分序列化，效率高，使用麻烦。三、BinderBinder类，实现了IBinder接口。主要是AIDL（多线程，多并发访问）和Messenger（底层还是AIDL,单线程处理）作用：跨进程通信的一种方式（1）客户端和服务端进行通信的媒介，bindService时，服务端返回一个Binder对象，客户端客户获取数据。（2）ServiceManager连接 各种Manager（ActivityManager、WindowManager等）和对应ManagerService的桥梁。四、Messenger信使，可以在不同的进程中传递Message对象，在Message中放入要传递的数据特点：对AIDL做了封装，一次只能处理一个请求。流程图：使用步骤：1、服务端
public class MessengerService extends Service {    private static String TAG = "MessengerService";    private Messenger messenger = new Messenger(new MessageHandler());    @Override    public void onCreate() {        super.onCreate();    }    @Nullable    @Override    public IBinder onBind(Intent intent) {    //返回这个messenger对象底层的Binder        return messenger.getBinder();    }    //处理服务端发送来的数据    private static class MessageHandler extends Handler{        @Override        public void handleMessage(Message msg) {            String myText = msg.getData().getString("msg");            LogUtil.i(TAG,"收到的消息："+myText);            //回复消息            Messenger client = msg.replyTo;            Message replyMessage = Message.obtain(null,2);            Bundle bundle = new Bundle();            bundle.putString("reply","收到了消息了啊");            replyMessage.setData(bundle);            try {                //做出回复                client.send(replyMessage);            }catch (RemoteException e){                e.printStackTrace();            }        }    }}清单文件配置：
<service android:name=".service.MessengerService"    android:process=":remote"    ></service>2、客户端
/** * * 用户端 */public class MainActivity extends BaseActivity{    private Messenger messenger;    @Override    protected int getContentViewID() {        return R.layout.activity_main;    }    @Override    public void initView() {        super.initView();        Intent intent = new Intent(this, MessengerService.class);        bindService(intent,connection,BIND_AUTO_CREATE);    }    private Messenger replyMessenger = new Messenger(new MessageHandler());    private static class MessageHandler extends Handler {        @Override        public void handleMessage(Message msg) {            String myText = msg.getData().getString("reply");            LogUtil.i(TAG,"客户端收到的消息："+myText);        }    }    private ServiceConnection connection = new ServiceConnection() {        @Override        public void onServiceConnected(ComponentName name, IBinder service) {            //绑定成功后，用服务端返回的IBinder来创建一个Messenger            //通过这个Messenger向服务端发消息            messenger = new Messenger(service);            Message message = Message.obtain(null,1);            Bundle bundle = new Bundle();            bundle.putString("msg","ssssss");            message.setData(bundle);            //客户端接收到服务端回复的消息            message.replyTo = replyMessenger;            try {                //发送消息                messenger.send(message);            }catch (RemoteException e){                e.printStackTrace();            }        }        @Override        public void onServiceDisconnected(ComponentName name) {            LogUtil.i("链接断开");        }    };    @Override    protected void onDestroy() {        super.onDestroy();        unbindService(connection);    }}五、AIDL:1、创建实体类，实现Parcelable
public class Book implements Parcelable {    public int bookId;    public String bookName;    public Book(int bookId,String bookName){        this.bookId=bookId;        this.bookName = bookName;    }    protected Book(Parcel in) {        bookId = in.readInt();        bookName = in.readString();    }    @Override    public String toString() {        return "["+bookId+"---"+bookName+"]";    }    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 int describeContents() {        return 0;    }    @Override    public void writeToParcel(Parcel dest, int flags) {        dest.writeString(bookName);        dest.writeInt(bookId);    }}2、AIDL接口的实现：（1）AIDL文件支持的数据类型基本数据类型（int、long、char、boolean、double等）String和CharSequenceArrayList ： 里面的元素必须能被AIDL支持HashMapParcelable：实现了Parcelable接口的对象注：其中Parcelable对象和AIDL对象显式import进来创建一个AIDL文件，将需要给客户端调用的接口在AIDL文件中声明
// IBookManager.aidlpackage com.example.hejian.demo2.aidl;//导入所需要使用的非默认支持数据类型的包import com.example.hejian.demo2.aidl.Book;interface IBookManager{List<Book> getBookList();void add(in Book book);}（2）如果有自定义Parcelable对象，必须建一个同名的AIDL文件
// Book.aidl//这个文件的作用是引入了一个序列化对象 Book 供其他的AIDL文件使用//注意：Book.aidl与Book.java的包名应当是一样的package com.example.hejian.demo2.aidl;parcelable Book;3、服务端创建一个Service，在Service中实现这个AIDL接口。注：AIDL方法是在服务端的Binder线程池中执行，可能出现并发访问的情况（可使用CopyOnWriteArrayList进行并发访问）4、绑定服务端的Service，通过服务器返回的Binder对象转成AIDL接口所需类型。5、专门删除跨进程的listener的接口RemoteCallbackList。客户端进程终止，自动移除客户端注册的listener原理：内部有一个map专门保存所有的AIDL回调，map的key时IBinder类型，value是Callback类型（真正的远程listener）他们底层的Binder对象是同一个，将相同的key的listener删除掉就可。
// IOnNewBookArrivedListener.aidlpackage com.example.hejian.aidldemo;// Declare any non-default types here with import statementsimport com.example.hejian.aidldemo.Book;//新书到了的监听interface IOnNewBookArrivedListener {    void onNewBookArrived(in Book newBook);}服务端Service:
/** * 服务端 */public class AIDLService extends Service {    private CopyOnWriteArrayList<Book> mBooks = new CopyOnWriteArrayList<>();    public final String TAG = this.getClass().getSimpleName();    private RemoteCallbackList<IOnNewBookArrivedListener> backListener = new RemoteCallbackList<>();    @Override    public void onCreate() {        super.onCreate();        mBooks.add(new Book(13,"思维"));        mBooks.add(new Book(23,"思维1"));    }    private Binder binder= new IBookManager.Stub(){        @Override        public List<Book> getBookList() throws RemoteException {            Log.e(TAG, "获取到服务端list : " + mBooks.toString());            return mBooks;        }        @Override        public void add(Book book) throws RemoteException {            mBooks.add(book);            //通过监听通知所有的客户端            final int N = backListener.beginBroadcast();            for (int i=0;i<N;i++){                IOnNewBookArrivedListener listener = backListener.getBroadcastItem(i);                listener.onNewBookArrived(book);            }            backListener.finishBroadcast();            Log.e(TAG, "增加一本以后，服务端list : " + mBooks.toString());        }        @Override        public void registListener(IOnNewBookArrivedListener listener) throws RemoteException {            backListener.register(listener);        }        @Override        public void unregistListener(IOnNewBookArrivedListener listener) throws RemoteException {            backListener.unregister(listener);        }    };    @Nullable    @Override    public IBinder onBind(Intent intent) {        return binder;    }}用户端：
public class MainActivity extends AppCompatActivity {    //由AIDL文件生成的Java类    private IBookManager mBookManager = null;    //包含Book对象的list    private List<Book> mBooks = new ArrayList<>();    private static String TAG = "MainActivity";    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Button button = (Button)findViewById(R.id.button);        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                try {                    if (mBookManager!=null){                        mBooks.add(new Book(23,"新增的"));                        mBookManager.add(new Book(23,"新增的"));                    }                } catch (RemoteException e) {                    e.printStackTrace();                }                Log.e(TAG, "增加一本以后，客户端list : "+mBooks.toString());            }        });    }    @Override    protected void onResume() {        super.onResume();        Intent intent = new Intent(this, AIDLService.class);        bindService(intent, mServiceConnection, Context.BIND_AUTO_CREATE);    }    private final ServiceConnection mServiceConnection = new ServiceConnection() {        @Override        public void onServiceConnected(ComponentName name, IBinder service) {            Log.e(TAG, "service connected");            //将服务端返回的Binder对象转成AIDL接口，然后通过接口掉方法            mBookManager = IBookManager.Stub.asInterface(service);            if (mBookManager != null) {                try {                    mBookManager.registListener(listener);                    mBooks = mBookManager.getBookList();                    Log.e(TAG, "获取客户端list："+mBooks.toString());                } catch (RemoteException e) {                    e.printStackTrace();                }            }        }        @Override        public void onServiceDisconnected(ComponentName name) {            Log.e(TAG, "service disconnected");        }    };    private IOnNewBookArrivedListener listener = new IOnNewBookArrivedListener.Stub() {        @Override        public void onNewBookArrived(Book newBook) throws RemoteException {            Log.e(TAG,"监听到服务器加了一个书："+newBook.toString());        }    };    @Override    protected void onDestroy() {        super.onDestroy();        unbindService(mServiceConnection);    }}6、Binder死亡监听（1）设置DeathRecipient监听，在binderDied方法中重连远程服务（在Binder线程池中被回调）（2）在onServiceDisconnected中重连远程服务7、远程服务的权限验证（1）例如在清单文件声明权限，在Service的onBind方法中做权限验证（2）在服务端onTransact方法验证（3）获取Uid和Pid，验证客户端包名等注意：由于客户端onServiceConnected和onServiceDisConnected方法运行在UI线程，不能直接进行耗时操作服务端本身运行在Binder线程池中，可以执行大量的耗时操作。注：开发艺术探索笔记整理