android进程间通信:AIDL

srp 2013-05-04

  欢迎阅读本文,你能关注本文,你知道你需要进程间通信、需要AIDL(以及Binder),那么可以默认你对这些概念已经有了一些了解,你(大致)知道它们是什么,它们有什么用,所以为了节约大家的眼力和时间,在此我不复制粘贴网上泛滥的博客或者翻译冗长的android文档。

      关于AIDL的介绍在文档:docs/guide/developing/tools/aidl.html

      关于IBinder的介绍在文档:docs/reference/android/os/IBinder.html

      以及Binder:docs/reference/android/os/Binder.html

      在后文中,我将以我自己的理解向你介绍相关的概念。以我目前粗浅的经验,应用程序使用AIDL的地方,几乎都和Service有关,所以你也需要知道一些关于Service的知识。日后得闲我也会继续写一些关于Service的贴。

      本文将以一个例子来和你分享使用AIDL的基础技能,这个例子里有:

1、一个类mAIDLActivity,继承Activity。里面有三个按钮,text分别为StartService,StopService,CallbackTest。

2、一个类mAIDLService,继承Service。为了充分展示ADIL的功能,它做以下工作:当用户点击CallbackTest按钮时,从mAIDLActivity调用mAIDLService中的Stub 对象的一个方法invokCallBack(),而这个方法又会调用mAIDLActivity中Stub 对象的一个方法performAction(),这个方法在屏幕上显示一个toast。没什么意义,只是展示一下AIDL如何使用。

3、两个AIDL文件:forService.aidl和forActivity.aidl。对应名字,在Service和Activity中分别有对象需要用到它们定义的接口。

4、相关XML文件,略过。关于manifest中Service的语法,见docs/guide/topics/manifest/service-element.html。你也可以简单地在<application></application>中加入

     <service android:name=".mAIDLService" android:process=":remote"> </service>

开发环境为Eclipse。

拣重要的先说,来看看aidl文件的内容:

文件:forActivity.aidl

package com.styleflying.AIDL;  

interface forActivity {  


    void performAction();  

    }  

package com.styleflying.AIDL;interface forActivity { void performAction(); }  

文件:forService.aidl

package com.styleflying.AIDL;  

import com.styleflying.AIDL.forActivity;  


interface forService {  


    void registerTestCall(forActivity cb);  


    void invokCallBack();  

}  

package com.styleflying.AIDL;import com.styleflying.AIDL.forActivity;interface forService { void registerTestCall(forActivity cb); void invokCallBack();}  

这两个文件和Java文件放置的地方一样,看包名。

在Eclipse中它们将被自动编译为forActivity.java和forService.java,它们存放在gen目录下。为了方便手头无法演练的读者,代码贴上,不用细看。

文件forActivity.java:

/* 
 * This file is auto-generated.  DO NOT MODIFY. 
 * Original file: D://workspace//AIDLTest//src//com//styleflying//AIDL//forActivity.aidl 
 */  

package com.styleflying.AIDL;  


import java.lang.String;  


import android.os.RemoteException;  


import android.os.IBinder;  


import android.os.IInterface;  


import android.os.Binder;  


import android.os.Parcel;  


public interface forActivity extends android.os.IInterface  

{  

/** Local-side IPC implementation stub class. */  


public static abstract class Stub extends android.os.Binder implements com.styleflying.AIDL.forActivity  

{  

private static final java.lang.String DESCRIPTOR = "com.styleflying.AIDL.forActivity";  


/** Construct the stub at attach it to the interface. */  


public Stub()  

{  

this.attachInterface(this, DESCRIPTOR);  

}  

/** 
 * Cast an IBinder object into an forActivity interface, 
 * generating a proxy if needed. 
 */  

public static com.styleflying.AIDL.forActivity asInterface(android.os.IBinder obj)  

{  

if ((obj==null)) {  


return null;  

}  
android.os.IInterface iin = (android.os.IInterface)obj.queryLocalInterface(DESCRIPTOR);  

if (((iin!=null)&&(iin instanceof com.styleflying.AIDL.forActivity))) {  


return ((com.styleflying.AIDL.forActivity)iin);  

}  

return new com.styleflying.AIDL.forActivity.Stub.Proxy(obj);  

}  

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_performAction:  

{  
data.enforceInterface(DESCRIPTOR);  

this.performAction();  

reply.writeNoException();  

return true;  

}  
}  

return super.onTransact(code, data, reply, flags);  

}  

private static class Proxy implements com.styleflying.AIDL.forActivity  

{  

private android.os.IBinder mRemote;  

Proxy(android.os.IBinder remote)  
{  
mRemote = remote;  
}  

public android.os.IBinder asBinder()  

{  

return mRemote;  

}  

public java.lang.String getInterfaceDescriptor()  

{  

return DESCRIPTOR;  

}  

public void performAction() throws android.os.RemoteException  

{  
android.os.Parcel _data = android.os.Parcel.obtain();  
android.os.Parcel _reply = android.os.Parcel.obtain();  

try {  

_data.writeInterfaceToken(DESCRIPTOR);  

mRemote.transact(Stub.TRANSACTION_performAction, _data, _reply, 0);  

_reply.readException();  
}  

finally {  

_reply.recycle();  
_data.recycle();  
}  
}  
}  

static final int TRANSACTION_performAction = (IBinder.FIRST_CALL_TRANSACTION + 0);  

}  

public void performAction() throws android.os.RemoteException;  

}  

/* * This file is auto-generated. DO NOT MODIFY. * Original file: D://workspace//AIDLTest//src//com//styleflying//AIDL//forActivity.aidl */package com.styleflying.AIDL;import java.lang.String;import android.os.RemoteException;import android.os.IBinder;import android.os.IInterface;import android.os.Binder;import android.os.Parcel;public interface forActivity extends android.os.IInterface{/** Local-side IPC implementation stub class. */public static abstract class Stub extends android.os.Binder implements com.styleflying.AIDL.forActivity{private static final java.lang.String DESCRIPTOR = "com.styleflying.AIDL.forActivity";/** Construct the stub at attach it to the interface. */public Stub(){this.attachInterface(this, DESCRIPTOR);}/** * Cast an IBinder object into an forActivity interface, * generating a proxy if needed. */public static com.styleflying.AIDL.forActivity asInterface(android.os.IBinder obj){if ((obj==null)) {return null;}android.os.IInterface iin = (android.os.IInterface)obj.queryLocalInterface(DESCRIPTOR);if (((iin!=null)&&(iin instanceof com.styleflying.AIDL.forActivity))) {return ((com.styleflying.AIDL.forActivity)iin);}return new com.styleflying.AIDL.forActivity.Stub.Proxy(obj);}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_performAction:{data.enforceInterface(DESCRIPTOR);this.performAction();reply.writeNoException();return true;}}return super.onTransact(code, data, reply, flags);}private static class Proxy implements com.styleflying.AIDL.forActivity{private android.os.IBinder mRemote;Proxy(android.os.IBinder remote){mRemote = remote;}public android.os.IBinder asBinder(){return mRemote;}public java.lang.String getInterfaceDescriptor(){return DESCRIPTOR;}public void performAction() throws android.os.RemoteException{android.os.Parcel _data = android.os.Parcel.obtain();android.os.Parcel _reply = android.os.Parcel.obtain();try {_data.writeInterfaceToken(DESCRIPTOR);mRemote.transact(Stub.TRANSACTION_performAction, _data, _reply, 0);_reply.readException();}finally {_reply.recycle();_data.recycle();}}}static final int TRANSACTION_performAction = (IBinder.FIRST_CALL_TRANSACTION + 0);}public void performAction() throws android.os.RemoteException;}

文件forService.java:

/* 
 * This file is auto-generated.  DO NOT MODIFY. 
 * Original file: D://workspace//AIDLTest//src//com//styleflying//AIDL//forService.aidl 
 */  

package com.styleflying.AIDL;  


import java.lang.String;  


import android.os.RemoteException;  


import android.os.IBinder;  


import android.os.IInterface;  


import android.os.Binder;  


import android.os.Parcel;  


public interface forService extends android.os.IInterface  

{  

/** Local-side IPC implementation stub class. */  


public static abstract class Stub extends android.os.Binder implements com.styleflying.AIDL.forService  

{  

private static final java.lang.String DESCRIPTOR = "com.styleflying.AIDL.forService";  


/** Construct the stub at attach it to the interface. */  


public Stub()  

{  

this.attachInterface(this, DESCRIPTOR);  

}  

/** 
 * Cast an IBinder object into an forService interface, 
 * generating a proxy if needed. 
 */  

public static com.styleflying.AIDL.forService asInterface(android.os.IBinder obj)  

{  

if ((obj==null)) {  


return null;  

}  
android.os.IInterface iin = (android.os.IInterface)obj.queryLocalInterface(DESCRIPTOR);  

if (((iin!=null)&&(iin instanceof com.styleflying.AIDL.forService))) {  


return ((com.styleflying.AIDL.forService)iin);  

}  

return new com.styleflying.AIDL.forService.Stub.Proxy(obj);  

}  

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_registerTestCall:  

{  
data.enforceInterface(DESCRIPTOR);  
com.styleflying.AIDL.forActivity _arg0;  
_arg0 = com.styleflying.AIDL.forActivity.Stub.asInterface(data.readStrongBinder());  

this.registerTestCall(_arg0);  

reply.writeNoException();  

return true;  

}  

case TRANSACTION_invokCallBack:  

{  
data.enforceInterface(DESCRIPTOR);  

this.invokCallBack();  

reply.writeNoException();  

return true;  

}  
}  

return super.onTransact(code, data, reply, flags);  

}  

private static class Proxy implements com.styleflying.AIDL.forService  

{  

private android.os.IBinder mRemote;  

Proxy(android.os.IBinder remote)  
{  
mRemote = remote;  
}  

public android.os.IBinder asBinder()  

{  

return mRemote;  

}  

public java.lang.String getInterfaceDescriptor()  

{  

return DESCRIPTOR;  

}  

public void registerTestCall(com.styleflying.AIDL.forActivity cb) 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.writeStrongBinder((((cb!=null))?(cb.asBinder()):(null)));  


mRemote.transact(Stub.TRANSACTION_registerTestCall, _data, _reply, 0);  

_reply.readException();  
}  

finally {  

_reply.recycle();  
_data.recycle();  
}  
}  

public void invokCallBack() throws android.os.RemoteException  

{  
android.os.Parcel _data = android.os.Parcel.obtain();  
android.os.Parcel _reply = android.os.Parcel.obtain();  

try {  

_data.writeInterfaceToken(DESCRIPTOR);  

mRemote.transact(Stub.TRANSACTION_invokCallBack, _data, _reply, 0);  

_reply.readException();  
}  

finally {  

_reply.recycle();  
_data.recycle();  
}  
}  
}  

static final int TRANSACTION_registerTestCall = (IBinder.FIRST_CALL_TRANSACTION + 0);  


static final int TRANSACTION_invokCallBack = (IBinder.FIRST_CALL_TRANSACTION + 1);  

}  

public void registerTestCall(com.styleflying.AIDL.forActivity cb) throws android.os.RemoteException;  


public void invokCallBack() throws android.os.RemoteException;  

}  

/* * This file is auto-generated. DO NOT MODIFY. * Original file: D://workspace//AIDLTest//src//com//styleflying//AIDL//forService.aidl */package com.styleflying.AIDL;import java.lang.String;import android.os.RemoteException;import android.os.IBinder;import android.os.IInterface;import android.os.Binder;import android.os.Parcel;public interface forService extends android.os.IInterface{/** Local-side IPC implementation stub class. */public static abstract class Stub extends android.os.Binder implements com.styleflying.AIDL.forService{private static final java.lang.String DESCRIPTOR = "com.styleflying.AIDL.forService";/** Construct the stub at attach it to the interface. */public Stub(){this.attachInterface(this, DESCRIPTOR);}/** * Cast an IBinder object into an forService interface, * generating a proxy if needed. */public static com.styleflying.AIDL.forService asInterface(android.os.IBinder obj){if ((obj==null)) {return null;}android.os.IInterface iin = (android.os.IInterface)obj.queryLocalInterface(DESCRIPTOR);if (((iin!=null)&&(iin instanceof com.styleflying.AIDL.forService))) {return ((com.styleflying.AIDL.forService)iin);}return new com.styleflying.AIDL.forService.Stub.Proxy(obj);}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_registerTestCall:{data.enforceInterface(DESCRIPTOR);com.styleflying.AIDL.forActivity _arg0;_arg0 = com.styleflying.AIDL.forActivity.Stub.asInterface(data.readStrongBinder());this.registerTestCall(_arg0);reply.writeNoException();return true;}case TRANSACTION_invokCallBack:{data.enforceInterface(DESCRIPTOR);this.invokCallBack();reply.writeNoException();return true;}}return super.onTransact(code, data, reply, flags);}private static class Proxy implements com.styleflying.AIDL.forService{private android.os.IBinder mRemote;Proxy(android.os.IBinder remote){mRemote = remote;}public android.os.IBinder asBinder(){return mRemote;}public java.lang.String getInterfaceDescriptor(){return DESCRIPTOR;}public void registerTestCall(com.styleflying.AIDL.forActivity cb) 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.writeStrongBinder((((cb!=null))?(cb.asBinder()):(null)));mRemote.transact(Stub.TRANSACTION_registerTestCall, _data, _reply, 0);_reply.readException();}finally {_reply.recycle();_data.recycle();}}public void invokCallBack() throws android.os.RemoteException{android.os.Parcel _data = android.os.Parcel.obtain();android.os.Parcel _reply = android.os.Parcel.obtain();try {_data.writeInterfaceToken(DESCRIPTOR);mRemote.transact(Stub.TRANSACTION_invokCallBack, _data, _reply, 0);_reply.readException();}finally {_reply.recycle();_data.recycle();}}}static final int TRANSACTION_registerTestCall = (IBinder.FIRST_CALL_TRANSACTION + 0);static final int TRANSACTION_invokCallBack = (IBinder.FIRST_CALL_TRANSACTION + 1);}public void registerTestCall(com.styleflying.AIDL.forActivity cb) throws android.os.RemoteException;public void invokCallBack() throws android.os.RemoteException;}

两段代码差不多,前面基本一样,从后面看,最后跟着我们在AIDL中自定义的方法,没有实现。两个文件各定义一个了接口,这两个接口分别会在Activity和Service中使用,在那里我们将实现自定义的方法。两个接口中都定义了一个抽象类Stub,实现所在的接口。Stub中又有一个类Proxy。Stub中有一个static的asInterface()方法,里面有很多return语句,在mAIDLActivity中调用它时,它返回一个新创建的内部类Proxy对象。

这个Stub对我们来说很有用,它继承了Binder。Binder有什么用呢?一个类,继承了Binder,那么它的对象就可以被远程的进程使用了(前提是远程进程获取了这个类的对象【对象的引用】,至于如如何获得看下文),在本例中就是说,如果一个Service中有一个继承了Stub的类的对象,那么这个对象中的方法就可以在Activity中使用,对Activity也是这样。至于Binder的细节,网上有很多贴介绍,看不明白也不影响我们完成这个例子。

再看mAIDLActivity.java:

package com.styleflying.AIDL;  

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.util.Log;  


import android.view.View;  


import android.view.View.OnClickListener;  


import android.widget.Button;  


import android.widget.Toast;  


public class mAIDLActivity extends Activity {  


    private static final String TAG = "AIDLActivity";  


    private Button btnOk;  


    private Button btnCancel;  


    private Button btnCallBack;  

      

    private void Log(String str) {  


        Log.d(TAG, "------ " + str + "------");  

        }  
      

    private forActivity mCallback = new forActivity.Stub() {  


        public void performAction() throws RemoteException  

        {  

            Toast.makeText(mAIDLActivity.this, "this toast is called from service", 1).show();  

        }  
        };  
          
    forService mService;  

    private ServiceConnection mConnection = new ServiceConnection() {  


        public void onServiceConnected(ComponentName className,  

                IBinder service) {  
            mService = forService.Stub.asInterface(service);  

            try {  

                mService.registerTestCall(mCallback);}  

            catch (RemoteException e) {  

                  
            }  
            }  

        public void onServiceDisconnected(ComponentName className) {  


            Log("disconnect service");  


            mService = null;  

            }  
        };  

    @Override  


    public void onCreate(Bundle icicle) {  


        super.onCreate(icicle);  

        setContentView(R.layout.main);  
        btnOk = (Button)findViewById(R.id.btn_ok);  
        btnCancel = (Button)findViewById(R.id.btn_cancel);  
        btnCallBack = (Button)findViewById(R.id.btn_callback);  

        btnOk.setOnClickListener(new OnClickListener() {  


            public void onClick(View v) {  


                Bundle args = new Bundle();  


                Intent intent = new Intent(mAIDLActivity.this, mAIDLService.class);  

                intent.putExtras(args);  
                bindService(intent, mConnection, Context.BIND_AUTO_CREATE);  
                startService(intent);  
                }  
            });  

        btnCancel.setOnClickListener(new OnClickListener() {  


            public void onClick(View v) {  

                unbindService(mConnection);  

                //stopService(intent);   

                }  
            });  

        btnCallBack.setOnClickListener(new OnClickListener() {  

              

            @Override  


            public void onClick(View v)  

            {  

                try  

                {  
                    mService.invokCallBack();  

                } catch (RemoteException e)  

                {  

                    // TODO Auto-generated catch block   

                    e.printStackTrace();  
                }  
            }  
        });  
        }  
}  

package com.styleflying.AIDL;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.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.Toast;public class mAIDLActivity extends Activity { private static final String TAG = "AIDLActivity"; private Button btnOk; private Button btnCancel; private Button btnCallBack; private void Log(String str) { Log.d(TAG, "------ " + str + "------"); } private forActivity mCallback = new forActivity.Stub() { public void performAction() throws RemoteException { Toast.makeText(mAIDLActivity.this, "this toast is called from service", 1).show(); } }; forService mService; private ServiceConnection mConnection = new ServiceConnection() { public void onServiceConnected(ComponentName className, IBinder service) { mService = forService.Stub.asInterface(service); try { mService.registerTestCall(mCallback);} catch (RemoteException e) { } } public void onServiceDisconnected(ComponentName className) { Log("disconnect service"); mService = null; } }; @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.main); btnOk = (Button)findViewById(R.id.btn_ok); btnCancel = (Button)findViewById(R.id.btn_cancel); btnCallBack = (Button)findViewById(R.id.btn_callback); btnOk.setOnClickListener(new OnClickListener() { public void onClick(View v) { Bundle args = new Bundle(); Intent intent = new Intent(mAIDLActivity.this, mAIDLService.class); intent.putExtras(args); bindService(intent, mConnection, Context.BIND_AUTO_CREATE); startService(intent); } }); btnCancel.setOnClickListener(new OnClickListener() { public void onClick(View v) { unbindService(mConnection); //stopService(intent); } }); btnCallBack.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { try { mService.invokCallBack(); } catch (RemoteException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }); }}

很短,相信大家很容易看明白。注意mConnection,它的onServiceConnected()中有一句mService = forService.Stub.asInterface(service);给mService赋值了,这个mService是一个forService,而service是onServiceConnected()传进来的参数,onServiceConnected()会在连接Service的时候被系统调用,这个service参数的值来自哪里呢?看mAIDLService.java:

package com.styleflying.AIDL;  

import android.app.Service;  


import android.content.Intent;  


import android.os.IBinder;  


import android.os.RemoteCallbackList;  


import android.os.RemoteException;  


import android.util.Log;  


public class mAIDLService extends Service {  


    private static final String TAG = "AIDLService";    


    private forActivity callback;  


    private void Log(String str) {  


        Log.d(TAG, "------ " + str + "------");  

    }  

    @Override  


    public void onCreate() {  


        Log("service create");  

    }  

    @Override  


    public void onStart(Intent intent, int startId) {  


        Log("service start id=" + startId);  

    }  
      

    @Override  


    public IBinder onBind(Intent t) {  


        Log("service on bind");  


        return mBinder;  

    }  

    @Override  


    public void onDestroy() {  


        Log("service on destroy");  


        super.onDestroy();  

    }  

    @Override  


    public boolean onUnbind(Intent intent) {  


        Log("service on unbind");  


        return super.onUnbind(intent);  

    }  

    public void onRebind(Intent intent) {  


        Log("service on rebind");  


        super.onRebind(intent);  

    }  

    private final forService.Stub mBinder = new forService.Stub() {  


        @Override  


        public void invokCallBack() throws RemoteException  

        {  
            callback.performAction();  
              
        }  

        @Override  


        public void registerTestCall(forActivity cb) throws RemoteException  

        {  
            callback = cb;  
              
        }  
          
    };  
}  

package com.styleflying.AIDL;import android.app.Service;import android.content.Intent;import android.os.IBinder;import android.os.RemoteCallbackList;import android.os.RemoteException;import android.util.Log;public class mAIDLService extends Service { private static final String TAG = "AIDLService"; private forActivity callback; private void Log(String str) { Log.d(TAG, "------ " + str + "------"); } @Override public void onCreate() { Log("service create"); } @Override public void onStart(Intent intent, int startId) { Log("service start id=" + startId); } @Override public IBinder onBind(Intent t) { Log("service on bind"); return mBinder; } @Override public void onDestroy() { Log("service on destroy"); super.onDestroy(); } @Override public boolean onUnbind(Intent intent) { Log("service on unbind"); return super.onUnbind(intent); } public void onRebind(Intent intent) { Log("service on rebind"); super.onRebind(intent); } private final forService.Stub mBinder = new forService.Stub() { @Override public void invokCallBack() throws RemoteException { callback.performAction(); } @Override public void registerTestCall(forActivity cb) throws RemoteException { callback = cb; } };}

注意onBind(),它的返回类型为IBinder,返回了一个mBinder,看看mBinder的定义:

    private final forService.Stub mBinder = new forService.Stub() {

        @Override
        public void invokCallBack() throws RemoteException
        {
            callback.performAction();
         }

        @Override
        public void registerTestCall(forActivity cb) throws RemoteException
        {
            callback = cb;

        }

       };

它是实现了我们在AIDL中定义的方法,这个mBinder最终返回给了mAIDLActivity中的mService,于是在mAIDLActivity中可以使用mBinder中的方法了。在mAIDLActivity中也有一个类似mBinder的对象,看看定义:   

        private forActivity mCallback = new forActivity.Stub()

    {
        public void performAction() throws RemoteException
        {
            Toast.makeText(mAIDLActivity.this, "this toast is called from service", 1).show();
        }
      };

我们要在界面上显示一个toast,就是在这里实现的。这个对象,在mConnection的onServiceConnected()被调用时,通过调用mService(也就是远程的mAIDLService中的mBinder)的registerTestCall(),传递给了mAIDLService,于是在mAIDLService中可以调用performAction()了。

很啰嗦,只为了能把这个细节说清楚。请大家认真看,我尽量避免错别字、混乱的大小写和逻辑不清的语法,相信你会看明白。是不是很简单?再啰嗦一下,做一个大致总结,我们使用AIDL是要做什么呢:

让Acticity(或者说一个进程/一个类?)和Service(或者说远端进程/远端类/对象?)获取对方的一个Stub对象,这个对象在定义时实现了我们在AIDL中定义的方法,于是这些远程对象中的方法可以在本地使用了。如果这种使用(通信)是单向的,比如只是Activity需要通知Service做什么,那么只要Service中有一个Stub对象,并且传给Acticity就够了。

至于如何获得远程的Stub,参看上面的代码,看mConnection、registerTestCall、onRebind,它们展示了一种方法。

另外,有时候我们可能在一个类中有多个Stub对象,它们都要给远程交互的类的实例,这个时候可以考虑使用RemoteCallbackList<>(docs/reference/android/os/RemoteCallbackList.html)。

欢迎阅读、收藏本文。例子随手写的,功能只在演示AIDL的使用。您可以转载本文,但请勿盲目乱贴。不是我小气,我不权威,我怕它被贴到泛滥,以讹传讹,害了人。

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