Android Binder的实战与原理
服务端编写
用AIDL生成一个Binder类
package com.example.myapplication; public interface BookAIDL extends android.os.IInterface { /** Local-side IPC implementation stub class. */ public static abstract class Stub extends android.os.Binder implements BookAIDL { private static final String DESCRIPTOR = "com.example.server.aidl.BookAIDL"; /** Construct the stub at attach it to the interface. */ public Stub() { this.attachInterface(this, DESCRIPTOR); } /** * Cast an IBinder object into an com.example.server.aidl.BookAIDL interface, * generating a proxy if needed. */ public static BookAIDL asInterface(android.os.IBinder obj) { if ((obj==null)) { return null; } android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR); if (((iin!=null)&&(iin instanceof BookAIDL))) { return ((BookAIDL)iin); } return new BookAIDL.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_getBookName: { data.enforceInterface(DESCRIPTOR); String _result = this.getBookName(); reply.writeNoException(); reply.writeString(_result); return true; } } return super.onTransact(code, data, reply, flags); } private static class Proxy implements BookAIDL { private android.os.IBinder mRemote; Proxy(android.os.IBinder remote) { mRemote = remote; } @Override public android.os.IBinder asBinder() { return mRemote; } public String getInterfaceDescriptor() { return DESCRIPTOR; } @Override public String getBookName() throws android.os.RemoteException { android.os.Parcel _data = android.os.Parcel.obtain(); android.os.Parcel _reply = android.os.Parcel.obtain(); String _result; try { _data.writeInterfaceToken(DESCRIPTOR); mRemote.transact(BookAIDL.Stub.TRANSACTION_getBookName, _data, _reply, 0); _reply.readException(); _result = _reply.readString(); } finally { _reply.recycle(); _data.recycle(); } return _result; } } static final int TRANSACTION_getBookName = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0); } public String getBookName() throws android.os.RemoteException; }
编写Service代码
package com.example.server; import android.app.Service; import android.content.Intent; import android.os.IBinder; import android.os.RemoteException; import com.example.server.aidl.BookAIDL; public class BookService extends Service { public BookService() {} @Override public IBinder onBind(Intent intent) { return binder; } private final BookAIDL.Stub binder = new BookAIDL.Stub() { @Override public String getBookName() { return "Android源代码情景分析"; } }; }
然后你必须在你的模拟器里安装这个server app
客户端编写
然后BookAIDL也需要拷贝到客户端
客户端调用
package com.example.myapplication; import android.app.Activity; 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.util.Log; public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Intent intent = new Intent(); intent.setComponent(new ComponentName("com.example.server", "com.example.server.BookService")); bindService(intent, connection, Context.BIND_AUTO_CREATE); } private static final String TAG = "xbh"; private ServiceConnection connection = new ServiceConnection() { @Override public void onServiceConnected(ComponentName name, IBinder service) { BookAIDL aidl = BookAIDL.Stub.asInterface(service); try { Log.i(TAG, aidl.getBookName()); } catch (RemoteException e) { e.printStackTrace(); } } @Override public void onServiceDisconnected(ComponentName name) { } }; @Override protected void onDestroy() { super.onDestroy(); unbindService(connection); } }
成功输出
其实简单的理解:ServiceManager管理所有的服务端,客户端从ServiceManager中去找服务端。
分析那个Binder类
public static BookAIDL asInterface(android.os.IBinder obj) { if ((obj == null)) { return null; } android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR); if (((iin != null) && (iin instanceof BookAIDL))) { return ((BookAIDL) iin); } return new BookAIDL.Stub.Proxy(obj); }
如果是同进程,我们直接返回服务端的对象。如果是异进程,需要封装一下。
@Override public boolean onTransact(int code, @NonNull 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_getBookName: { data.enforceInterface(DESCRIPTOR); String _result = this.getBookName(); reply.writeNoException(); reply.writeString(_result); return true; } } return super.onTransact(code, data, reply, flags); }
@Override public boolean onTransact(int code, @NonNull 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_getBookName: { data.enforceInterface(DESCRIPTOR); String _result = this.getBookName(); reply.writeNoException(); reply.writeString(_result); return true; } } return super.onTransact(code, data, reply, flags); }
这个方法运行在服务端的Binder线程池。
_data用来存放方法的输入参数,_reply是返回值