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*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。