AIDL Service，跨进程调用Services

一、AIDL Service简介

Android系统中，各个应用都运行在自己的进程中，进程之间一般无法直接进行通信，为了实现进程通信，Android提供了AIDL Service；

二、与本地Service不同
本地Service：直接把IBinder对象本身传递给客户端的ServiceConnection的onServiceConnected方法的第二个参数；

远程Service：只将IBinder对象的代理传给客户端的ServiceConnection的onServiceConnected方法的第二个参数；

三、AIDL文件

Android需要AIDL（Android Interface Definition Language）来定义远程接口，这种接口定义语言并不是一种真正的变成语言，只是定义两个进程之间的通信接口；

与Java接口相似，但是存在如下几点差异：

AIDL定义接口的源代码必须以.aidl结尾；

AIDL用到的数据类型，除了基本类型、String、List、Map、CharSequence之外，其它类型全部都需要导包，即使它们在同一个包中也需要导包；

四、例子：

1. 创建AIDL文件,定义好的AIDL文件后，ADT工具会自动在gen目录下生成一个AIDL.java接口，该类内部包含一个Stub内部类，实现了IBinder，AIDL里面的接口，这个Stub类会作为远程Service回调类：

IMyService.aidl
package com.juno.serviceaidltest;

import com.juno.serviceaidltest.Product;
interface IMyService
{
String getValue();
Map getMap(in String country, in Product product);
Product getProduct();
}

Product.aidl
parcelable Product;

Product.java
package com.juno.serviceaidltest;

import android.os.Parcel;
import android.os.Parcelable;

public class Product implements Parcelable {
private int id;
private String name;
private float price;
public static final Parcelable.Creator<Product> CREATOR = new Parcelable.Creator<Product>() {
public Product createFromParcel(Parcel in) {
return new Product(in);
}

public Product[] newArray(int size) {
return new Product[size];
}
};

public Product() {

}

private Product(Parcel in) {
readFromParcel(in);
}

@Override
public int describeContents() {
return 0;
}

public void readFromParcel(Parcel in) {
id = in.readInt();
name = in.readString();
price = in.readFloat();

}

@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(id);
dest.writeString(name);
dest.writeFloat(price);

}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public float getPrice() {
return price;
}

public void setPrice(float price) {
this.price = price;
}

}

2. 将接口暴露给客户端

MyService.java
package com.juno.serviceaidltest;

import java.util.HashMap;
import java.util.Map;

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

public class MyService extends Service {
/**
* 继承Stub,也就是实现了IMyService接口，并实现了IBinder接口
*/
public class MyServiceImpl extends IMyService.Stub {

@Override
public String getValue() throws RemoteException {
return "Test Value";
}

@Override
public Map<String, Object> getMap(String country, Product product)
throws RemoteException {
Map<String, Object> map = new HashMap<String, Object>();
map.put("country", country);
map.put("id", product.getId());
map.put("name", product.getName());
map.put("price", product.getPrice());
map.put("product", product);
return map;
}

@Override
public Product getProduct() throws RemoteException {
Product product = new Product();
product.setId(1234);
product.setName("汽车");
product.setPrice(31000);
return product;
}

}

@Override
public IBinder onBind(Intent intent) {
/**
* 返回MyServiceImpl对象，在绑定本地Service情况下，该MyServiceImpl会直接传给客户端的ServiceConnected对象的ServiceConnected()方法的第二个参数；在绑定远程Service的情况下，只将MyServiceImpl对象的代理传给客户端的ServiceConnected对象的ServiceConnected()方法的第二个参数
*/
return new MyServiceImpl();
}

}

3. 在AndroidManifext.xml文件中配置该Service:

<service android:name=".MyService" >
<intent-filter>
<action android:name="com.juno.serviceaidltest.IService" />
</intent-filter>
</service>

4. 在Activity里访问AIDLService,如果不在同一个App下面访问，需要将Service端的AIDL文件复制到客户端中，并在相同的包名下：

MainActivity.java
package com.juno.serviceanotheraidltest;

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.widget.Button;
import android.widget.TextView;

import com.juno.serviceaidltest.IMyService;

public class MainActivity extends Activity implements View.OnClickListener {

private final static String ACTION = "com.juno.serviceaidltest.IService";
private IMyService myService = null;
private Button mBtnInvokeAIDLService;
private Button mBtnBindAIDLService;
private TextView mTextView;
private ServiceConnection mServiceConnection = new ServiceConnection() {

@Override
public void onServiceConnected(ComponentName name, IBinder service) {
//获取远程Service的onBinder方法返回的对象代理
myService = IMyService.Stub.asInterface(service);
mBtnInvokeAIDLService.setEnabled(true);

try {
Log.v("juno", myService.getValue());
} catch (RemoteException e) {
e.printStackTrace();
}
}

@Override
public void onServiceDisconnected(ComponentName name) {
myService = null;
}
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}

private void initView() {
mBtnInvokeAIDLService = (Button) findViewById(R.id.btnInvokeAIDLService);
mBtnBindAIDLService = (Button) findViewById(R.id.btnBindAIDLService);
mBtnInvokeAIDLService.setEnabled(false);
mTextView = (TextView) findViewById(R.id.textView1);
mBtnInvokeAIDLService.setOnClickListener(this);
mBtnBindAIDLService.setOnClickListener(this);
}

@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.btnBindAIDLService:
//创建所需要绑定的Service的Intent，绑定远程的服务
bindService(new Intent(ACTION), mServiceConnection, Context.BIND_AUTO_CREATE);
break;

case R.id.btnInvokeAIDLService:
try {
String s = myService.getValue();
s = "Product.id = " + myService.getProduct().getId() + "\n";
s += "Product.name = " + myService.getProduct().getName()
+ "\n";
s += "Product.price = " + myService.getProduct().getPrice()
+ "\n";

s += myService.getMap("China", myService.getProduct()).toString();
mTextView.setText(myService.asBinder().isBinderAlive() + "  " + s);
} catch (Exception e) {

}
break;
}

}

@Override
protected void onDestroy() {
super.onDestroy();
if (myService != null) {
//解除绑定
unbindService(mServiceConnection);
}
}

}

布局文件

activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >

<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />

<Button
android:id="@+id/btnBindAIDLService"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/textView1"
android:text="btnBindAIDLService" />

<Button
android:id="@+id/btnInvokeAIDLService"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/btnBindAIDLService"
android:text="btnInvokeAIDLService" />

</RelativeLayout>