自顶向下分析Binder【1】—— Binder实例篇
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一个Binder实例
我们Binder的学习将从以下的一个实例開始。依据Android文档中的描写叙述,创建一个Binder服务主要包含例如以下3步:
以下详细看一下在eclipse中是怎样开发一个Binder应用的。
第一步:在project文件夹下定义aidl文件。
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package com.zxh.ipc; import com.zxh.ipc.PermissionInfo; interface ITestManager{ int checkPermission(String
permName, String pkgName); int checkUidPermission(String
permName, int uid); boolean addPermission(in
PermissionInfo info); void removePermission(String
name); boolean isProtectedBroadcast(String
actionName); } |
第二步:在定义aidl后,eclipse在project文件夹的gen文件夹下会自己主动生成相应的接口,以下是有aidl自己主动生成的Java代码:
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package com.zxh.ipc; public interface ITestManager extends android.os.IInterface { /**
Local-side IPC implementation stub class. */ public static abstract class Stub extends android.os.Binder implements com.zxh.ipc.ITestManager { private static final java.lang.String
DESCRIPTOR = "com.zxh.ipc.ITestManager" ; /**
Construct the stub at attach it to the interface. */ public Stub() { this .attachInterface( this ,
DESCRIPTOR); } /** *
Cast an IBinder object into an com.zxh.ipc.ITestManager interface, generating a proxy if needed. */ public static com.zxh.ipc.ITestManager
asInterface(android.os.IBinder obj) { if ((obj
== null ))
{ return null ; } android.os.IInterface
iin = obj.queryLocalInterface(DESCRIPTOR); if (((iin
!= null )
&& (iin instanceof com.zxh.ipc.ITestManager)))
{ return ((com.zxh.ipc.ITestManager)
iin); } return new com.zxh.ipc.ITestManager.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_checkPermission:
{ data.enforceInterface(DESCRIPTOR); java.lang.String
_arg0; _arg0
= data.readString(); java.lang.String
_arg1; _arg1
= data.readString(); int _result
= this .checkPermission(_arg0,
_arg1); reply.writeNoException(); reply.writeInt(_result); return true ; } case TRANSACTION_checkUidPermission:
{ data.enforceInterface(DESCRIPTOR); java.lang.String
_arg0; _arg0
= data.readString(); int _arg1; _arg1
= data.readInt(); int _result
= this .checkUidPermission(_arg0,
_arg1); reply.writeNoException(); reply.writeInt(_result); return true ; } case TRANSACTION_addPermission:
{ data.enforceInterface(DESCRIPTOR); com.zxh.ipc.PermissionInfo
_arg0; if (( 0 !=
data.readInt())) { _arg0
= com.zxh.ipc.PermissionInfo.CREATOR.createFromParcel(data); } else { _arg0
= null ; } boolean _result
= this .addPermission(_arg0); reply.writeNoException(); reply.writeInt(((_result)
? ( 1 )
: ( 0 ))); return true ; } case TRANSACTION_removePermission:
{ data.enforceInterface(DESCRIPTOR); java.lang.String
_arg0; _arg0
= data.readString(); this .removePermission(_arg0); reply.writeNoException(); return true ; } case TRANSACTION_isProtectedBroadcast:
{ data.enforceInterface(DESCRIPTOR); java.lang.String
_arg0; _arg0
= data.readString(); boolean _result
= this .isProtectedBroadcast(_arg0); reply.writeNoException(); reply.writeInt(((_result)
? ( 1 )
: ( 0 ))); return true ; } } return super .onTransact(code,
data, reply, flags); } private static class Proxy implements com.zxh.ipc.ITestManager { 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; } @Override public int checkPermission(java.lang.String
permName, java.lang.String pkgName) throws android.os.RemoteException { android.os.Parcel
_data = android.os.Parcel.obtain(); android.os.Parcel
_reply = android.os.Parcel.obtain(); int _result; try { _data.writeInterfaceToken(DESCRIPTOR); _data.writeString(permName); _data.writeString(pkgName); mRemote.transact(Stub.TRANSACTION_checkPermission,
_data, _reply, 0 ); _reply.readException(); _result
= _reply.readInt(); } finally { _reply.recycle(); _data.recycle(); } return _result; } @Override public int checkUidPermission(java.lang.String
permName, int uid) throws android.os.RemoteException { android.os.Parcel
_data = android.os.Parcel.obtain(); android.os.Parcel
_reply = android.os.Parcel.obtain(); int _result; try { _data.writeInterfaceToken(DESCRIPTOR); _data.writeString(permName); _data.writeInt(uid); mRemote.transact(Stub.TRANSACTION_checkUidPermission,
_data, _reply, 0 ); _reply.readException(); _result
= _reply.readInt(); } finally { _reply.recycle(); _data.recycle(); } return _result; } @Override public boolean addPermission(com.zxh.ipc.PermissionInfo
info) throws android.os.RemoteException { android.os.Parcel
_data = android.os.Parcel.obtain(); android.os.Parcel
_reply = android.os.Parcel.obtain(); boolean _result; try { _data.writeInterfaceToken(DESCRIPTOR); if ((info
!= null ))
{ _data.writeInt( 1 ); info.writeToParcel(_data, 0 ); } else { _data.writeInt( 0 ); } mRemote.transact(Stub.TRANSACTION_addPermission,
_data, _reply, 0 ); _reply.readException(); _result
= ( 0 !=
_reply.readInt()); } finally { _reply.recycle(); _data.recycle(); } return _result; } @Override public void removePermission(java.lang.String
name) throws android.os.RemoteException { android.os.Parcel
_data = android.os.Parcel.obtain(); android.os.Parcel
_reply = android.os.Parcel.obtain(); try { _data.writeInterfaceToken(DESCRIPTOR); _data.writeString(name); mRemote.transact(Stub.TRANSACTION_removePermission,
_data, _reply, 0 ); _reply.readException(); } finally { _reply.recycle(); _data.recycle(); } } @Override public boolean isProtectedBroadcast(java.lang.String
actionName) throws android.os.RemoteException { android.os.Parcel
_data = android.os.Parcel.obtain(); android.os.Parcel
_reply = android.os.Parcel.obtain(); boolean _result; try { _data.writeInterfaceToken(DESCRIPTOR); _data.writeString(actionName); mRemote.transact(Stub.TRANSACTION_isProtectedBroadcast,
_data, _reply, 0 ); _reply.readException(); _result
= ( 0 !=
_reply.readInt()); } finally { _reply.recycle(); _data.recycle(); } return _result; } } static final int TRANSACTION_checkPermission
= (android.os.IBinder.FIRST_CALL_TRANSACTION + 0 ); static final int TRANSACTION_checkUidPermission
= (android.os.IBinder.FIRST_CALL_TRANSACTION + 1 ); static final int TRANSACTION_addPermission
= (android.os.IBinder.FIRST_CALL_TRANSACTION + 2 ); static final int TRANSACTION_removePermission
= (android.os.IBinder.FIRST_CALL_TRANSACTION + 3 ); static final int TRANSACTION_isProtectedBroadcast
= (android.os.IBinder.FIRST_CALL_TRANSACTION + 4 ); } public int checkPermission(java.lang.String
permName, java.lang.String pkgName) throws android.os.RemoteException; public int checkUidPermission(java.lang.String
permName, int uid) throws android.os.RemoteException; public boolean addPermission(com.zxh.ipc.PermissionInfo
info) throws android.os.RemoteException; public void removePermission(java.lang.String
name) throws android.os.RemoteException; public boolean isProtectedBroadcast(java.lang.String
actionName) throws android.os.RemoteException; } |
第三步:继承上一步生成的接口,实现自己的Service类:
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package com.zxh.server; import android.app.Service; import android.content.Intent; import android.content.ServiceConnection; import android.os.IBinder; import android.os.RemoteException; import android.util.Log; import com.zxh.ipc.ITestManager; import com.zxh.ipc.PermissionInfo; public class TestService extends Service{ private final static String
TAG = "zxh" ; class TestManagerService extends ITestManager.Stub{ @Override public int checkPermission(String
permName, String pkgName) throws RemoteException
{ Log.i(TAG, "checkPermission
server" ); return 0 ; } @Override public int checkUidPermission(String
permName, int uid) throws RemoteException
{ Log.i(TAG, "checkUidPermission
server" ); return 0 ; } @Override public boolean addPermission(PermissionInfo
info) throws RemoteException
{ Log.i(TAG, "addPermission
server" ); return false ; } @Override public void removePermission(String
name) throws RemoteException
{ Log.i(TAG, "removePermission
server" ); } @Override public boolean isProtectedBroadcast(String
actionName) throws RemoteException
{ Log.i(TAG, "isProtectedBroadcast
server" ); return false ; } } private TestManagerService
mService = new TestManagerService(); @Override public IBinder
onBind(Intent intent) { Log.i( "zxh" , "unbindService" ); return mService; } @Override public void unbindService(ServiceConnection
conn) { super .unbindService(conn); Log.i( "zxh" , "unbindService" ); } } |
第四步:实现client代码:
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package com.zxh.server; import android.app.Activity; import android.app.Service; import android.content.ComponentName; import android.content.Intent; import android.content.ServiceConnection; import android.os.Bundle; import android.os.IBinder; import android.os.RemoteException; import android.util.Log; import android.view.View; import android.view.View.OnClickListener; import com.zxh.ipc.ITestManager; public class MainActivity extends Activity
{ private ITestManager
manager = null ; ServiceConnection
connection = new ServiceConnection()
{ @Override public void onServiceDisconnected(ComponentName
name) { Log.i( "binder" , "onServiceDisconnected" ); } @Override public void onServiceConnected(ComponentName
name, IBinder service) { manager
= ITestManager.Stub.asInterface(service); } }; @Override protected void onCreate(Bundle
savedInstanceState) { super .onCreate(savedInstanceState); setContentView(R.layout.activity_main); findViewById(R.id.startServer).setOnClickListener( new OnClickListener()
{ @Override public void onClick(View
v) { bindService( new Intent(MainActivity. this ,
TestService. class ),
connection, Service.BIND_AUTO_CREATE); } }); findViewById(R.id.stop).setOnClickListener( new OnClickListener()
{ @Override public void onClick(View
v) { unbindService(connection); } }); findViewById(R.id.check).setOnClickListener( new OnClickListener()
{ @Override public void onClick(View
v) { try { manager.checkPermission( "permName" , "pkgName" ); } catch (RemoteException
e) { e.printStackTrace(); } } }); } } |
到这里我们就实现了一个完整的Binder实例,以下是project文件夹的截图:
完整代码能够查看后面的附件。以下来介绍一下这个实例中涉及到的一些知识点。
AIDL
除了eclipse,也能够使用Android开发包中提供的aidl命令工具来生成,例如以下是adil命令:
关于adil的具体介绍能够查看Android官方文档,地址为:http://developer.android.com/intl/zh-cn/guide/components/aidl.html
想要了解aidl处理过程的朋友也能够自己查看aidl的源码,位于@/frameworks/base/tools/adil。
AIDL编译产生的类
以下我们来分析一下aidl编译产生的ITestManager类。
从ITestManager中能够看出,ITestManager实现了IInterface接口。在ITestManager类中共包括了三部分内容,各自是:
-
我们在ITestManager.adil中定义的接口。
-
Stub类:主要由Server端实现,Server端通过继承本类,来提供详细的处理逻辑。
-
Proxy类:client代理,通过mRemote成员变量訪问远程Binder服务。
为了实现我们在ITestManager自定义接口的跨进程通信,Stub类和Proxy都实现了ITestManager接口。Stub自己继承了Binder类来实现Binder机制,Proxy则以引用的方式实现Binder机制。
client和服务端的通信主要通过onTransact方法实现,client和服务端的数据传递通过Parcel类完毕。这里须要注意一个问题:就是在client写入数据的顺序与在服务端读取数据的顺序必须是一致的。
尽管在上面的实现中,我们定义了一个Service类TestService,但这里要说明的是Service甚至adil都不是必须的,使用者全然能够自定义。