android进程间通信(AIDL)开发

Home / Android MrLee 2015-5-29 2945

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。你也可以简单地在中加入

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();
	}
文件:forService.aidl
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;
}
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;
}
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();
				}
			}
		});
        }
}
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;
			
		}
        
    };
}
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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