Android多进程之手动编写Binder类

Android多进程系列

• Android 多进程通信之几个基本问题
• Android多进程之Binder的使用

分析系统生成的Binder类

package com.xxq2dream.aidl; public interface IBookManager extends android.os.IInterface { /** * Local-side IPC implementation stub class. */ public static abstract class Stub extends android.os.Binder implements com.xxq2dream.aidl.IBookManager { private static final java.lang.String DESCRIPTOR = "com.xxq2dream.aidl.IBookManager"; /** * Construct the stub at attach it to the interface. */ public Stub() { this.attachInterface(this, DESCRIPTOR); } /** * 用于将服务端的Binder对象转换成客户端所需要的AIDL接口类型的对象 */ public static com.xxq2dream.aidl.IBookManager asInterface(android.os.IBinder obj) { if ((obj == null)) { return null; } android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR); //这里通过instanceof方法判断是否是跨进程，如果客户端和服务端位于同一进程，则返回的是服务端的Stub对象本身，不会调用跨进程的transact方法 if (((iin != null) && (iin instanceof com.xxq2dream.aidl.IBookManager))) { return ((com.xxq2dream.aidl.IBookManager) iin); } //如果客户端和服务端不在同一个进程中，那么返回的是系统封装好的Stub.Proxy代理对象，客户端调用会走transact方法发起跨进程请求 return new com.xxq2dream.aidl.IBookManager.Stub.Proxy(obj); } //返回当前Binder对象 @Override public android.os.IBinder asBinder() { return this; } /** * 运行在服务端的Binder线程池中 * * @param code 要运行的方法标识 * @param data 客户端传递过来的参数 * @param reply 回传给客户端的数据 * @param flags * @return true 表示执行成功；false，执行失败，客户端的请求失败 * @throws RemoteException */ @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_getBookList: { data.enforceInterface(DESCRIPTOR); java.util.List<com.xxq2dream.aidl.Book> _result = this.getBookList(); reply.writeNoException(); //将结果写入reply返回 reply.writeTypedList(_result); return true; } case TRANSACTION_addBook: { data.enforceInterface(DESCRIPTOR); com.xxq2dream.aidl.Book _arg0; if ((0 != data.readInt())) { _arg0 = com.xxq2dream.aidl.Book.CREATOR.createFromParcel(data); } else { _arg0 = null; } this.addBook(_arg0); reply.writeNoException(); return true; } } return super.onTransact(code, data, reply, flags); } private static class Proxy implements com.xxq2dream.aidl.IBookManager { 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; } /** * 运行在客户端的Binder线程池中 * 当客户端和服务端不在同一个进程中时，通过上面的asInterface方法返回的就是这个Proxy对象 * 调用服务端的方法就是调用这里对应的方法，最终走的是transact方法发起远程过程调用 * * @return * @throws RemoteException */ @Override public java.util.List<com.xxq2dream.aidl.Book> getBookList() throws android.os.RemoteException { //用于向服务端传递参数 android.os.Parcel _data = android.os.Parcel.obtain(); //用于接收服务端传回来的结果 android.os.Parcel _reply = android.os.Parcel.obtain(); java.util.List<com.xxq2dream.aidl.Book> _result; try { _data.writeInterfaceToken(DESCRIPTOR); //发起远程过程调用请求，同时当前线程挂起，服务端的onTransact方法会被调用 mRemote.transact(Stub.TRANSACTION_getBookList, _data, _reply, 0); //上述调用过程返回后，当前线程继续执行，从reply中取出结果返回 _reply.readException(); _result = _reply.createTypedArrayList(com.xxq2dream.aidl.Book.CREATOR); } finally { _reply.recycle(); _data.recycle(); } return _result; } @Override public void addBook(com.xxq2dream.aidl.Book book) throws android.os.RemoteException { android.os.Parcel _data = android.os.Parcel.obtain(); android.os.Parcel _reply = android.os.Parcel.obtain(); try { _data.writeInterfaceToken(DESCRIPTOR); if ((book != null)) { _data.writeInt(1); book.writeToParcel(_data, 0); } else { _data.writeInt(0); } mRemote.transact(Stub.TRANSACTION_addBook, _data, _reply, 0); _reply.readException(); } finally { _reply.recycle(); _data.recycle(); } } } //接口的标识 static final int TRANSACTION_getBookList = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0); static final int TRANSACTION_addBook = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1); } //提供的接口 public java.util.List<com.xxq2dream.aidl.Book> getBookList() throws android.os.RemoteException; public void addBook(com.xxq2dream.aidl.Book book) throws android.os.RemoteException; } 

动手编写Binder类

• 从上面的分析可以看出Binder类主要可以分为2个部分，一个是Stub类，也就是真正的Binder类；另一个就是AIDL接口

抽取出AIDL接口

public interface IBookManager extends IInterface { static final String DESCRIPTOR = "com.xxq2dream.manualbinder.IBookManager"; static final int TRANSACTION_getBookList = IBinder.FIRST_CALL_TRANSACTION + 0; static final int TRANSACTION_addBook = IBinder.FIRST_CALL_TRANSACTION + 1; <!--注释1--> <!--static final int TRANSACTION_registerListener= IBinder.FIRST_CALL_TRANSACTION + 2;--> <!--static final int TRANSACTION_unRegisterListener= IBinder.FIRST_CALL_TRANSACTION + 3;--> public List<Book> getBookList() throws RemoteException; public void addBook(Book book) throws RemoteException; <!--注释2--> <!--void registerListener(IOnNewBookArrivedListener listener) throws RemoteException;--> <!--void unRegisterListener(IOnNewBookArrivedListener listener) throws RemoteException;--> }

实现Stub类和Stub类的代理类

• 这个和上面自动生成的代码大部分都是一样的

public class BookManagerImpl extends Binder implements IBookManager { private static final String TAG = "BookManagerImpl"; public BookManagerImpl() { Log.e(TAG, "attachInterface-->"+ System.currentTimeMillis()); this.attachInterface(this,DESCRIPTOR); } /** * Cast an IBinder object into an com.xxq2dream.IBookManager interface, * generating a proxy if needed. */ public static IBookManager asInterface(IBinder obj) { if ((obj == null)) { return null; } android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR); if (((iin != null) && (iin instanceof IBookManager))) { Log.e(TAG, "asInterface"); return ((IBookManager) iin); } Log.e(TAG, "asInterface Proxy-->"+ System.currentTimeMillis()); return new BookManagerImpl.Proxy(obj); } /** * 运行在服务端的Binder线程池中 * * @param code 要运行的方法标识 * @param data 客户端传递过来的参数 * @param reply 回传给客户端的数据 * @param flags * @return true 表示执行成功；false，执行失败，客户端的请求失败 * @throws RemoteException */ @Override public boolean onTransact(int code, Parcel data, Parcel reply, int flags) throws RemoteException { Log.e(TAG, "onTransact-->"+System.currentTimeMillis()); switch (code) { case INTERFACE_TRANSACTION: { Log.e(TAG, "INTERFACE_TRANSACTION-->"+ System.currentTimeMillis()); reply.writeString(DESCRIPTOR); return true; } case TRANSACTION_getBookList: { Log.e(TAG, "TRANSACTION_getBookList-->"+ System.currentTimeMillis()); data.enforceInterface(DESCRIPTOR); List<Book> result = this.getBookList(); reply.writeNoException(); reply.writeTypedList(result); return true; } case TRANSACTION_addBook: { Log.e(TAG, "TRANSACTION_addBook-->"+ System.currentTimeMillis()); data.enforceInterface(DESCRIPTOR); Book arg0; if (0 != data.readInt()) { arg0 = Book.CREATOR.createFromParcel(data); }else { arg0 = null; } this.addBook(arg0); reply.writeNoException(); return true; } <!--注释6--> <!--case TRANSACTION_registerListener: {--> <!-- Log.e(TAG, "TRANSACTION_registerListener-->" +System.currentTimeMillis());--> <!-- data.enforceInterface(DESCRIPTOR);--> <!-- IOnNewBookArrivedListener arg0;--> <!-- arg0 = OnNewBookArrivedListenerImpl.asInterface(data.readStrongBinder());--> <!-- this.registerListener(arg0);--> <!-- reply.writeNoException();--> <!-- return true;--> <!--}--> <!--case TRANSACTION_unRegisterListener: {--> <!-- Log.e(TAG, "TRANSACTION_unRegisterListener-->" +System.currentTimeMillis());--> <!-- data.enforceInterface(DESCRIPTOR);--> <!-- IOnNewBookArrivedListener arg0;--> <!-- arg0 = OnNewBookArrivedListenerImpl.asInterface(data.readStrongBinder());--> <!-- this.unRegisterListener(arg0);--> <!-- reply.writeNoException();--> <!-- return true;--> <!--}--> } return super.onTransact(code, data, reply, flags); } @Override public List<Book> getBookList() throws RemoteException { return null; } @Override public void addBook(Book book) throws RemoteException { } <!--注释5--> <!--@Override--> <!--public void registerListener(IOnNewBookArrivedListener listener) {--> <!--}--> <!--@Override--> <!--public void unRegisterListener(IOnNewBookArrivedListener listener) {--> <!--}--> /** * Retrieve the Binder object associated with this interface. * You must use this instead of a plain cast, so that proxy objects * can return the correct result. */ @Override public IBinder asBinder() { Log.e(TAG, "asBinder-->"+ System.currentTimeMillis()); return this; } private static class Proxy implements IBookManager { private IBinder mRemote; Proxy(IBinder remote) { mRemote = remote; } public String getInterfaceDescriptor() { return DESCRIPTOR; } /** * 运行在客户端的Binder线程池中 * * @return * @throws RemoteException */ @Override public List<Book> getBookList() throws RemoteException { Log.e(TAG, "Proxy-->getBookList-->"+ System.currentTimeMillis()); //用于向服务端传递参数 Parcel data = Parcel.obtain(); //用于接收服务端传回来的结果 Parcel reply = Parcel.obtain(); List<Book> result; try { data.writeInterfaceToken(DESCRIPTOR); //发起远程过程调用请求，同时当前线程挂起，服务端的onTransact方法会被调用 mRemote.transact(TRANSACTION_getBookList, data, reply, 0); //上述调用过程返回后，当前线程继续执行，从reply中取出结果返回 reply.readException(); result = reply.createTypedArrayList(Book.CREATOR); } finally { reply.recycle(); data.recycle(); } return result; } @Override public void addBook(Book book) throws RemoteException { Log.e(TAG, "Proxy-->addBook-->"+ System.currentTimeMillis()); //用于向服务端传递参数 Parcel data = Parcel.obtain(); //用于接收服务端传回来的结果 Parcel reply = Parcel.obtain(); try { data.writeInterfaceToken(DESCRIPTOR); if (book != null) { data.writeInt(1); book.writeToParcel(data,0); }else { data.writeInt(0); } mRemote.transact(TRANSACTION_addBook, data, reply, 0); reply.readException(); }finally { reply.recycle(); data.recycle(); } } <!--注释3--> <!--@Override--> <!--public void registerListener(IOnNewBookArrivedListener listener) throws RemoteException{--> <!-- Log.e(TAG, "Proxy-->registerListener-->"+ System.currentTimeMillis());--> <!-- //用于向服务端传递参数--> <!-- Parcel data = Parcel.obtain();--> <!-- //用于接收服务端传回来的结果--> <!-- Parcel reply = Parcel.obtain();--> <!-- try {--> <!-- data.writeInterfaceToken(DESCRIPTOR);--> <!-- data.writeStrongBinder((listener != null)?(listener.asBinder()) : (null));--> <!-- mRemote.transact(TRANSACTION_registerListener, data, reply, 0);--> <!-- reply.readException();--> <!-- }finally {--> <!-- reply.recycle();--> <!-- data.recycle();--> <!-- }--> <!--}--> <!--注释4--> <!--@Override--> <!--public void unRegisterListener(IOnNewBookArrivedListener listener) throws RemoteException{--> <!-- Log.e(TAG, "Proxy-->unRegisterListener-->"+ System.currentTimeMillis());--> <!-- //用于向服务端传递参数--> <!-- Parcel data = Parcel.obtain();--> <!-- //用于接收服务端传回来的结果--> <!-- Parcel reply = Parcel.obtain();--> <!-- try {--> <!-- data.writeInterfaceToken(DESCRIPTOR);--> <!-- data.writeStrongBinder((listener != null)?(listener.asBinder()) : (null));--> <!-- mRemote.transact(TRANSACTION_unRegisterListener, data, reply, 0);--> <!-- reply.readException();--> <!-- }finally {--> <!-- reply.recycle();--> <!-- data.recycle();--> <!-- }--> <!--}--> /** * Retrieve the Binder object associated with this interface. * You must use this instead of a plain cast, so that proxy objects * can return the correct result. */ @Override public IBinder asBinder() { Log.e(TAG, "Proxy-->asBinder-->"+ System.currentTimeMillis()); return mRemote; } } }

• 以上就是我们自己动手写的Binder类，没有使用系统的方法，也不用编写AIDL文件

扩展我们的Binder类

• 比如我们要实现当服务端有新书时就通知客户端，也就是观察者模式。我们需要在客户端绑定服务端后绑定监听的接口，还要提供解绑的接口，上面的代码中标记的注释1-6就是扩展Binder类的步骤
• 当然，由于AIDL中不支持普通的接口，只支持AIDL接口，我们要增加服务端的AIDL接口服务，像上面的代码里那样传递的接口肯定就是AIDL实现的接口，也就是
• 所以我们还得增加AIDL接口，同样的我们可以通过编写AIDL文件然后由系统自动生成，也可以手动编写。这里我们还是以手动的方式编写
• AIDL接口IOnNewBookArrivedListener

public interface IOnNewBookArrivedListener extends IInterface { static final String DESCRIPTOR = "com.xxq2dream.aidl.IOnNewBookArrivedListener"; static final int TRANSACTION_onNewBookArrived = IBinder.FIRST_CALL_TRANSACTION + 0; void onNewBookArrived(Book book) throws RemoteException; }

• 对应的Binder类

public class OnNewBookArrivedListenerImpl extends Binder implements IOnNewBookArrivedListener { private static final String TAG = "NewBookArrivedListener"; public OnNewBookArrivedListenerImpl() { Log.e(TAG, "attachInterface-->"+ System.currentTimeMillis()); this.attachInterface(this,DESCRIPTOR); } public static IOnNewBookArrivedListener asInterface (IBinder obj) { if ((obj == null)) { return null; } android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR); if (((iin != null) && (iin instanceof IOnNewBookArrivedListener))) { Log.e(TAG, "asInterface"); return ((IOnNewBookArrivedListener) iin); } Log.e(TAG, "asInterface Proxy-->"+ System.currentTimeMillis()); return new OnNewBookArrivedListenerImpl.Proxy(obj); } /** * 运行在服务端的Binder线程池中 * * @param code 要运行的方法标识 * @param data 客户端传递过来的参数 * @param reply 回传给客户端的数据 * @param flags * @return true 表示执行成功；false，执行失败，客户端的请求失败 * @throws RemoteException */ @Override public boolean onTransact(int code, Parcel data, Parcel reply, int flags) throws RemoteException { Log.e(TAG, "onTransact-->"+System.currentTimeMillis()); switch (code) { case INTERFACE_TRANSACTION: { Log.e(TAG, "INTERFACE_TRANSACTION-->"+ System.currentTimeMillis()); reply.writeString(DESCRIPTOR); return true; } case TRANSACTION_onNewBookArrived: { Log.e(TAG, "TRANSACTION_onNewBookArrived-->"+ System.currentTimeMillis()); data.enforceInterface(DESCRIPTOR); Book _arg0; if ((0 != data.readInt())) { _arg0 = Book.CREATOR.createFromParcel(data); } else { _arg0 = null; } this.onNewBookArrived(_arg0); reply.writeNoException(); return true; } } return super.onTransact(code, data, reply, flags); } @Override public void onNewBookArrived(Book book) { } /** * Retrieve the Binder object associated with this interface. * You must use this instead of a plain cast, so that proxy objects * can return the correct result. */ @Override public IBinder asBinder() { return this; } private static class Proxy implements IOnNewBookArrivedListener { private IBinder mRemote; Proxy(IBinder remote) { mRemote = remote; } public String getInterfaceDescriptor() { return DESCRIPTOR; } /** * Retrieve the Binder object associated with this interface. * You must use this instead of a plain cast, so that proxy objects * can return the correct result. */ @Override public IBinder asBinder() { Log.e(TAG, "Proxy-->asBinder-->"+ System.currentTimeMillis()); return mRemote; } @Override public void onNewBookArrived(Book newBook) throws RemoteException{ Log.e(TAG, "onNewBookArrived-->" + System.currentTimeMillis()); android.os.Parcel _data = android.os.Parcel.obtain(); android.os.Parcel _reply = android.os.Parcel.obtain(); try { _data.writeInterfaceToken(DESCRIPTOR); if ((newBook != null)) { _data.writeInt(1); newBook.writeToParcel(_data, 0); } else { _data.writeInt(0); } mRemote.transact(TRANSACTION_onNewBookArrived, _data, _reply, 0); _reply.readException(); } finally { _reply.recycle(); _data.recycle(); } } } }

Binder传递AIDL接口

• 通过上面的代码我们可以看到，和传递普通的Parcelable序列化对象不同的是，在Proxy类中要通过writeStrongBinder方法将AIDL接口加入到参数中去
• 在服务端的onTransact方法中要通过对应的Binder类的asInterface方法获得传递过来的接口参数

IOnNewBookArrivedListener arg0; arg0 = OnNewBookArrivedListenerImpl.asInterface(data.readStrongBinder());

结语

• 通过手动编写Binder类，可以让我们更好地理解Binder的工作机制
• 扩展了Binder类以后，下一步我们还需要相应的改造客户端和服务端，以便增加注册监听的功能

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