Service与BroadcastReceiver——（5）跨进程调用Service

我们都知道在Android中的每一个应用是一个进程，其实每一个应用就相当于Linux系统里面的一个用户，进程和进程之间的通信其实就相当于用户和用户之间的通信，为了实现这种跨进程通信，Android提供了AIDL Service (Android Interface definition language).

与邦等本地Service不同的是，本地Service的onBind()方法会直接把IBinder对象本身传给客户端的ServiceConnection的onServiceConnected方法的第二个参数。但远程Service的onBind()方法只是将IBinder对象的代理传给客户端的ServiceConnection的onService Connected方法的第二个参数。

ALDL定义的特点：

1、AIDL定义接口的源码必须以.aidl结尾。

2、AIDL接口中用到数据类型，除了基本类型、String、List、Map、CharSequence之外，其他类型全部都需要导包，即使它们在同一个包中也需要导包。

下面来具体实现一个示例：

（1）定义AIDL接口(和Java接口非常类似)

package com.example.testservice;

interface ICat {
	String getColor();
	double getWeight();
}

（2）定以好上面接口后保存，ADT工具会自动在gen.com.example.service目录下生成一个ICat.jar接口，在该接口中包含一个Stub内部类，该内部类实现了IBinder、ICat两个接口，这个Stub类将会作为远程Service的回调类——它实现了IBuilder接口，因此可作为Service的onBind()方法的返回值。这个Stub类就是一个代理类，同样可以实现IBinder的功能，并且还额外实现了ICat远程访问的功能。

自动生成的ICat.java接口

/*
 * This file is auto-generated.  DO NOT MODIFY.
 * Original file: D:\\adt-bundle-windows-x86-20130729\\eclipse\\workspace\\TestService\\src\\com\\example\\testservice\\ICat.aidl
 */
package com.example.testservice;

public interface ICat extends android.os.IInterface {
	/** Local-side IPC implementation stub class. */
	public static abstract class Stub extends android.os.Binder implements
			com.example.testservice.ICat {
		private static final java.lang.String DESCRIPTOR = "com.example.testservice.ICat";

		/** Construct the stub at attach it to the interface. */
		public Stub() {
			this.attachInterface(this, DESCRIPTOR);
		}

		/**
		 * Cast an IBinder object into an com.example.testservice.ICat
		 * interface, generating a proxy if needed.
		 */
		public static com.example.testservice.ICat asInterface(
				android.os.IBinder obj) {
			if ((obj == null)) {
				return null;
			}
			android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
			if (((iin != null) && (iin instanceof com.example.testservice.ICat))) {
				return ((com.example.testservice.ICat) iin);
			}
			return new com.example.testservice.ICat.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_getColor: {
				data.enforceInterface(DESCRIPTOR);
				java.lang.String _result = this.getColor();
				reply.writeNoException();
				reply.writeString(_result);
				return true;
			}
			case TRANSACTION_getWeight: {
				data.enforceInterface(DESCRIPTOR);
				double _result = this.getWeight();
				reply.writeNoException();
				reply.writeDouble(_result);
				return true;
			}
			}
			return super.onTransact(code, data, reply, flags);
		}

		private static class Proxy implements com.example.testservice.ICat {
			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 java.lang.String getColor()
					throws android.os.RemoteException {
				android.os.Parcel _data = android.os.Parcel.obtain();
				android.os.Parcel _reply = android.os.Parcel.obtain();
				java.lang.String _result;
				try {
					_data.writeInterfaceToken(DESCRIPTOR);
					mRemote.transact(Stub.TRANSACTION_getColor, _data, _reply,
							0);
					_reply.readException();
					_result = _reply.readString();
				} finally {
					_reply.recycle();
					_data.recycle();
				}
				return _result;
			}

			@Override
			public double getWeight() throws android.os.RemoteException {
				android.os.Parcel _data = android.os.Parcel.obtain();
				android.os.Parcel _reply = android.os.Parcel.obtain();
				double _result;
				try {
					_data.writeInterfaceToken(DESCRIPTOR);
					mRemote.transact(Stub.TRANSACTION_getWeight, _data, _reply,
							0);
					_reply.readException();
					_result = _reply.readDouble();
				} finally {
					_reply.recycle();
					_data.recycle();
				}
				return _result;
			}
		}

		static final int TRANSACTION_getColor = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
		static final int TRANSACTION_getWeight = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1);
	}

	public java.lang.String getColor() throws android.os.RemoteException;

	public double getWeight() throws android.os.RemoteException;
}

（3）定义一个Service实现类，该Service的onBind()方法所返回的IBinder对象应该是ADT所生成的ICat.Stub的子类的实例。这一步的主要作用是将上面创建的接口暴漏给客户端。

package com.example.testservice;

import java.util.Timer;
import java.util.TimerTask;

import com.example.testservice.ICat.Stub;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.RemoteException;

public class AidlService extends Service{
	
	private CatBinder catBinder;
	Timer timer = new Timer();
	String[] colors = new String[]{
			"红色",
			"黄色",
			"黑色"
	};
	double[] weights = new double[]{
			2.3,
			3.1,
			1.58
	};
	
	private String color;
	private double weight;

	
	@Override
	public IBinder onBind(Intent intent) {	
		/*
		 * 返回catBinder对象
		 * 在绑定本地Service的情况下，该catBinder对象会直接传给客户端的
		 * ServiceConnection对象的onServiceConnected方法的第二个参数；
		 * 在绑定远程Service的情况下，只将catBinder对象的代理传给客户端的
		 * ServiceConnection对象的onServiceConnected方法的第二个参数；
		 */
		return catBinder;
	}
	
	//继承Stub，也就是实现了ICat接口，并实现了IBinder接口
	public class CatBinder extends Stub{

		@Override
		public String getColor() throws RemoteException {
			// TODO Auto-generated method stub
			return color;
		}

		@Override
		public double getWeight() throws RemoteException {
			// TODO Auto-generated method stub
			return weight;
		}
		
	}
	
	@Override
	public void onCreate() {
		super.onCreate();
		catBinder = new CatBinder();
		timer.schedule(new TimerTask() {
			
			@Override
			public void run() {
				int rand = (int)(Math.random() * 3);
				color = colors[rand];
				weight = weights[rand];
				System.out.println("---------" + rand);
			}
		}, 0, 800);
	}

}

（4）在AndroidMainfest.xml文件中配置该Service

        <service android:name=".AidlService">
            <intent-filter>
                <action android:name="com.example.testservice.action.AIDL_SERVICE"/>
            </intent-filter>
        </service>

（5）客户端访问AIDL Service

上面说过AIDL是定义在两个进程之间通信的一个接口，既然是一个通信协议，客户端同样需要前面定义的AIDL接口，所以第一步就是将AIDL文件复制到客户端应用中。

package com.example.testservice;

import android.app.Activity;
import android.app.Service;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.IBinder;
import android.os.RemoteException;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class AidlClient extends Activity{
	private ICat catService;
	private Button get;
	EditText color, weight;
	private ServiceConnection conn = new ServiceConnection() {
		
		@Override
		public void onServiceDisconnected(ComponentName name) {
			
		}
		
		@Override
		public void onServiceConnected(ComponentName name, IBinder service) {
			//获取远程Service的onBind方法返回的对象的代理
			catService = ICat.Stub.asInterface(service);
		}
	};
	
	protected void onCreate(android.os.Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		get = (Button)findViewById(R.id.get);
		color = (EditText)findViewById(R.id.color);
		weight = (EditText)findViewById(R.id.weight);
		//创建所需绑定的Service的Intent
		Intent intent = new Intent();
		intent.setAction("com.example.testservice.action.AIDL_SERVICE");
		bindService(intent, conn, Service.BIND_AUTO_CREATE);
		get.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View arg0) {
				try {
					color.setText(catService.getColor());
					weight.setText(catService.getWeight() + "");
				} catch (RemoteException e) {
					e.printStackTrace();
				}
			}
		});
	};
	
	@Override
	protected void onDestroy() {
		super.onDestroy();
		//解除绑定
		this.unbindService(conn);
	}
}

下一篇将介绍如何在进程之间传递复杂数据