Android 进程间通信工具 AIDL

热度 ℃

在使用Binder进行进程间通信，服务端和客户端进行数据传递时，数据的传递(请求、响应)需要将数据打包成Parcel数据包，Parcel数据包写入和读取都需要按相同的顺序，给编码工作造成额外的工作量。而AIDL作为一个工具，可以将符合规范的aidl文件转换为java文件，将数据打包，解包成Parcel的工作给我们实现了，让我们专注于核心业务。

aidl文件

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// IAidlEx.aidl
package com.ccflying;
// Declare any non-default types here with import statements
interface IAidlEx {
    int getAge(String name);
    boolean setNameAndAge(String name, int age);
}

上面的aidl文件中，定义了两个接口，编译器会自动生成IAidlEx.java文件。

IAidlEx.java

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public interface IAidlEx extends android.os.IInterface
{
    /** Local-side IPC implementation stub class. */
    public static abstract class Stub extends android.os.Binder implements com.ccflying.IAidlEx {
    
        private static class Proxy implements com.ccflying.IAidlEx {
        
        }
        // ...
    }
    // ...
}

编译工具生成的IAidlEx文件中，定义了三个类，分别是:

  • IAidlEx: 接口定义，该类里面包含了aidl文件中定义的两个方法。
  • IAidlEx.Stub: 内部类Stub，继承自Binder，并且实现了IAidlEx接口，具体业务实现，由Stub子类实现，服务端需要继承此类，实现接口中定义的方法。
  • IAidlEx.Stub.Proxy: 内部类Stub.Proxy，在客户端中使用，用于向服务端发起请求，主要工作是将数据打包，调用mRemote.transact发起请求，获取服务端的响应结果。

IAidlEx

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public interface IAidlEx extends android.os.IInterface
{
    public int getAge(java.lang.String name) throws android.os.RemoteException;
    public boolean setNameAndAge(java.lang.String name, int age) throws android.os.RemoteException;
}

IAidlEx.Stub

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public static abstract class Stub extends android.os.Binder implements com.ccflying.IAidlEx {
     private static final java.lang.String DESCRIPTOR = "com.ccflying.IAidlEx";
     /** Construct the stub at attach it to the interface. */
     public Stub() {
         this.attachInterface(this, DESCRIPTOR);
     }
     /**
      * Cast an IBinder object into an com.ccflying.IAidlEx interface,
      * generating a proxy if needed.
      */
     public static com.ccflying.IAidlEx asInterface(android.os.IBinder obj) {
         if ((obj==null)) {
             return null;
         }
         android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
         if (((iin!=null)&&(iin instanceof com.ccflying.IAidlEx))) {
             return ((com.ccflying.IAidlEx)iin);
         }
         return new com.ccflying.IAidlEx.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_getAge:
             {
                 data.enforceInterface(DESCRIPTOR);
                 java.lang.String _arg0;
                 _arg0 = data.readString();
                 int _result = this.getAge(_arg0);
                 reply.writeNoException();
                 reply.writeInt(_result);
                 return true;
             }
             case TRANSACTION_setNameAndAge:
             {
                 data.enforceInterface(DESCRIPTOR);
                 java.lang.String _arg0;
                 _arg0 = data.readString();
                 int _arg1;
                 _arg1 = data.readInt();
                 boolean _result = this.setNameAndAge(_arg0, _arg1);
                 reply.writeNoException();
                 reply.writeInt(((_result)?(1):(0)));
                 return true;
             }
         }
         return super.onTransact(code, data, reply, flags);
     }
     static final int TRANSACTION_getAge = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1);
     static final int TRANSACTION_setNameAndAge = (android.os.IBinder.FIRST_CALL_TRANSACTION + 2);
 }

onTransact方法中，根据请求标识，解包数据包 -> 调用业务方法 -> 打包数据包返回。

IAidlEx.Stub.Proxy

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private static class Proxy implements com.ccflying.IAidlEx {
    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 getAge(java.lang.String name) 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(name);
            mRemote.transact(Stub.TRANSACTION_getAge, _data, _reply, 0);
            _reply.readException();
            _result = _reply.readInt();
        }
        finally {
            _reply.recycle();
            _data.recycle();
        }
        return _result;
    }
    @Override public boolean setNameAndAge(java.lang.String name, int age) 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(name);
            _data.writeInt(age);
            mRemote.transact(Stub.TRANSACTION_setNameAndAge, _data, _reply, 0);
            _reply.readException();
            _result = (0!=_reply.readInt());
        }
        finally {
            _reply.recycle();
            _data.recycle();
        }
        return _result;
    }
}

实现了IAidlEx接口，调用mRemote.transact向远程服务端发起请求。

实现Service服务

继承IAidlEx.Stub类，实现远程服务Binder业务。

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public class AidlExServiceImpl extends IAidlEx.Stub {
    final String TAG = "AidlExServiceImpl";
    private HashMap<String, Integer> users;
    public AidlExServiceImpl() {
        users = new HashMap<>();
    }
    @Override
    public int getAge(String name) throws RemoteException {
        Log.e(TAG, "getAge: " + name);
        Integer it = users.get(name);
        if (null == it)
            return -1;
        return it.intValue();
    }
    @Override
    public boolean setNameAndAge(String name, int age) throws RemoteException {
        Log.e(TAG, "setNameAndAge: " + name + ", " + age);
        users.put(name, age);
        return true;
    }
}

继承Service类，实现远程服务AidlExService。

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public class AidlExService extends Service {
    private final String TAG = "AidlExService";
    private AidlExServiceImpl serviceImpl;
    @Override
    public void onCreate() {
        super.onCreate();
        Log.e(TAG, "onCreate: ");
        serviceImpl = new AidlExServiceImpl();
    }
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        Log.e(TAG, "onBind: " + serviceImpl.hashCode());
        return serviceImpl;
    }
    @Override
    public boolean onUnbind(Intent intent) {
        Log.e(TAG, "onUnbind: ");
        return super.onUnbind(intent);
    }
}

发布服务

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<service android:name="com.ccflying.AidlExService"
         android:process=":remote" />

跨进程调用Service

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conn = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        // service : android.os.BinderProxy@6fb8e95
        mAidlExService = IAidlEx.Stub.asInterface(service);
        // mAidlExService: com.ccflying.IAidlEx$Stub$Proxy
    }
    @Override
    public void onServiceDisconnected(ComponentName name) {
        conn = null;
    }
};
bindService(new Intent(this, AidlExService.class), conn, Service.BIND_AUTO_CREATE);
// 请求setNameAndAge
boolean rs = mAidlExService.setNameAndAge("ccf", 27);
// 请求getAge
int age = mAidlExService.getAge("ccf");