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自顶向下分析Binder【1】—— Binder实例篇

2024-07-25 05:30:38   223人阅读

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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 = http://www.mamicode.com/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 = http://www.mamicode.com/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 = http://www.mamicode.com/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 = http://www.mamicode.com/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 = http://www.mamicode.com/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。

自顶向下分析Binder【1】—— Binder实例篇


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