編輯：關於Android編程
一、前言
Android中的RPC參考了JAVA中的RMI(remote methord invocation)方案；Android中的RPC機制是為了實現進程間通信，即一個進程使用另一個進程中的遠程對象，Android用AIDL(android interface defined language，Android接口定義語言)來實現，使用戶可以很方便的定義一套接口，然後通過遠程Service為代理，客戶端在綁定該遠程Service時，獲得遠程對象，然後就可以使用該對象。
二、流程
1. 定義一個.aidl接口文件，ADT則會在gen目錄下，自動生成一個對應的.java文件(此文件為自動生成，不可修改)；
2. 自動生成的.java中，有一個抽象的Stub類，因此，創建一個基於Stub的子類，並實現在.aidl中定義的接口；
3. 創建一個Service子類，在onCreate中，創建步驟2中的實例對象，在onBind中，返回該實例對象；
4. 在Activity中，發送一個bindService(it, conn, BIND_AUTO_CREATE)，請求綁定遠程Service；
5. 若成功，則在ServiceConnection.onServiceConnected中獲得步驟3中的實例對象；
6. 在AndroidManifest.xml中，注冊遠程Service；
三、例子
按照流程中的步驟，實現該例子：
3.1 定義.aidl文件
[java]
package com.chris.rpc.aidl;
interface ITest {
void setCustomerName(String name);
String getCustomerName();
}
package com.chris.rpc.aidl;
interface ITest {
void setCustomerName(String name);
String getCustomerName();
}很簡單，定義了兩個接口，然後，ADT就會自動在gen目錄下生成ITest.java文件，我們來看看：
[java]
/*
* This file is auto-generated. DO NOT MODIFY.
* Original file: E:\\chris\\Android_Dev\\eclipse\\workspace\\RpcAidl\\src\\com\\chris\\rpc\\aidl\\ITest.aidl
*/
package com.chris.rpc.aidl;
public interface ITest extends android.os.IInterface
{
/** Local-side IPC implementation stub class. */
public static abstract class Stub extends android.os.Binder implements com.chris.rpc.aidl.ITest
{
private static final java.lang.String DESCRIPTOR = "com.chris.rpc.aidl.ITest";
/** Construct the stub at attach it to the interface. */
public Stub()
{
this.attachInterface(this, DESCRIPTOR);
}
/**
* Cast an IBinder object into an com.chris.rpc.aidl.ITest interface,
* generating a proxy if needed.
*/
public static com.chris.rpc.aidl.ITest asInterface(android.os.IBinder obj)
{
if ((obj==null)) {
return null;
}
android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
if (((iin!=null)&&(iin instanceof com.chris.rpc.aidl.ITest))) {
return ((com.chris.rpc.aidl.ITest)iin);
}
return new com.chris.rpc.aidl.ITest.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_setCustomerName:
{
data.enforceInterface(DESCRIPTOR);
java.lang.String _arg0;
_arg0 = data.readString();
this.setCustomerName(_arg0);
reply.writeNoException();
return true;
}
case TRANSACTION_getCustomerName:
{
data.enforceInterface(DESCRIPTOR);
java.lang.String _result = this.getCustomerName();
reply.writeNoException();
reply.writeString(_result);
return true;
}
}
return super.onTransact(code, data, reply, flags);
}
private static class Proxy implements com.chris.rpc.aidl.ITest
{
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 void setCustomerName(java.lang.String name) 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.writeString(name);
mRemote.transact(Stub.TRANSACTION_setCustomerName, _data, _reply, 0);
_reply.readException();
}
finally {
_reply.recycle();
_data.recycle();
}
}
@Override public java.lang.String getCustomerName() 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_getCustomerName, _data, _reply, 0);
_reply.readException();
_result = _reply.readString();
}
finally {
_reply.recycle();
_data.recycle();
}
return _result;
}
}
static final int TRANSACTION_setCustomerName = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
static final int TRANSACTION_getCustomerName = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1);
}
public void setCustomerName(java.lang.String name) throws android.os.RemoteException;
public java.lang.String getCustomerName() throws android.os.RemoteException;
}
/*
* This file is auto-generated. DO NOT MODIFY.
* Original file: E:\\chris\\Android_Dev\\eclipse\\workspace\\RpcAidl\\src\\com\\chris\\rpc\\aidl\\ITest.aidl
*/
package com.chris.rpc.aidl;
public interface ITest extends android.os.IInterface
{
/** Local-side IPC implementation stub class. */
public static abstract class Stub extends android.os.Binder implements com.chris.rpc.aidl.ITest
{
private static final java.lang.String DESCRIPTOR = "com.chris.rpc.aidl.ITest";
/** Construct the stub at attach it to the interface. */
public Stub()
{
this.attachInterface(this, DESCRIPTOR);
}
/**
* Cast an IBinder object into an com.chris.rpc.aidl.ITest interface,
* generating a proxy if needed.
*/
public static com.chris.rpc.aidl.ITest asInterface(android.os.IBinder obj)
{
if ((obj==null)) {
return null;
}
android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
if (((iin!=null)&&(iin instanceof com.chris.rpc.aidl.ITest))) {
return ((com.chris.rpc.aidl.ITest)iin);
}
return new com.chris.rpc.aidl.ITest.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_setCustomerName:
{
data.enforceInterface(DESCRIPTOR);
java.lang.String _arg0;
_arg0 = data.readString();
this.setCustomerName(_arg0);
reply.writeNoException();
return true;
}
case TRANSACTION_getCustomerName:
{
data.enforceInterface(DESCRIPTOR);
java.lang.String _result = this.getCustomerName();
reply.writeNoException();
reply.writeString(_result);
return true;
}
}
return super.onTransact(code, data, reply, flags);
}
private static class Proxy implements com.chris.rpc.aidl.ITest
{
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 void setCustomerName(java.lang.String name) 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.writeString(name);
mRemote.transact(Stub.TRANSACTION_setCustomerName, _data, _reply, 0);
_reply.readException();
}
finally {
_reply.recycle();
_data.recycle();
}
}
@Override public java.lang.String getCustomerName() 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_getCustomerName, _data, _reply, 0);
_reply.readException();
_result = _reply.readString();
}
finally {
_reply.recycle();
_data.recycle();
}
return _result;
}
}
static final int TRANSACTION_setCustomerName = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
static final int TRANSACTION_getCustomerName = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1);
}
public void setCustomerName(java.lang.String name) throws android.os.RemoteException;
public java.lang.String getCustomerName() throws android.os.RemoteException;
}
3.2 創建Stub子類，並實現接口：
[java]
package com.chris.rpc.aidl;
import android.os.RemoteException;
import android.util.Log;
import com.chris.rpc.aidl.ITest.Stub;
public class MyTest extends Stub {
private final static String TAG = "ChrisRpcAidl";
private String strName = "";
@Override
public void setCustomerName(String name) throws RemoteException {
Log.d(TAG, "[MyTest] setCustomerName name = " + name);
strName = name;
}
@Override
public String getCustomerName() throws RemoteException {
Log.d(TAG, "[MyTest] getCustomerName name = " + strName);
return strName;
}
}
package com.chris.rpc.aidl;
import android.os.RemoteException;
import android.util.Log;
import com.chris.rpc.aidl.ITest.Stub;
public class MyTest extends Stub {
private final static String TAG = "ChrisRpcAidl";
private String strName = "";
@Override
public void setCustomerName(String name) throws RemoteException {
Log.d(TAG, "[MyTest] setCustomerName name = " + name);
strName = name;
}
@Override
public String getCustomerName() throws RemoteException {
Log.d(TAG, "[MyTest] getCustomerName name = " + strName);
return strName;
}
}
3.3 創建遠程Service類：
[java]
package com.chris.rpc.aidl;
import com.chris.rpc.aidl.ITest.Stub;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
public class MyService extends Service {
private final static String TAG = "ChrisRpcAidl";
private Stub mTest = null;
@Override
public IBinder onBind(Intent arg0) {
Log.d(TAG, "onBind ...");
return mTest;
}
@Override
public void onCreate() {
Log.d(TAG, "onCreate ...");
mTest = new MyTest();
super.onCreate();
}
}
package com.chris.rpc.aidl;
import com.chris.rpc.aidl.ITest.Stub;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
public class MyService extends Service {
private final static String TAG = "ChrisRpcAidl";
private Stub mTest = null;
@Override
public IBinder onBind(Intent arg0) {
Log.d(TAG, "onBind ...");
return mTest;
}
@Override
public void onCreate() {
Log.d(TAG, "onCreate ...");
mTest = new MyTest();
super.onCreate();
}
}
3.4 在Activity中請求綁定該遠程Service，並獲取實例：
[java]
package com.chris.rpc.aidl;
import android.os.Bundle;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
public class MainActivity extends Activity {
private final static String TAG = "ChrisRpcAidl";
private final static String SERVICE_ACTION = "com.chris.rpc.aidl.action.MYSERVICE";
private ITest mTest = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent it = new Intent();
it.setAction(SERVICE_ACTION);
// 發送綁定Service請求，如果成功，則會調用ServiceConnection
bindService(it, conn, BIND_AUTO_CREATE);
}
private ServiceConnection conn = new ServiceConnection(){
// 綁定成功，返回的對象是IBinder接口，通過asInterface轉換為定義的ITest接口
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
Log.d(TAG, "onServiceConnected ...");
mTest = ITest.Stub.asInterface(service);
if(mTest != null){
try {
mTest.setCustomerName("chris");
Log.d(TAG, "-------------------");
Log.d(TAG, "get name = " + mTest.getCustomerName());
} catch (RemoteException e) {
e.printStackTrace();
}
}
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
}
package com.chris.rpc.aidl;
import android.os.Bundle;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
public class MainActivity extends Activity {
private final static String TAG = "ChrisRpcAidl";
private final static String SERVICE_ACTION = "com.chris.rpc.aidl.action.MYSERVICE";
private ITest mTest = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent it = new Intent();
it.setAction(SERVICE_ACTION);
// 發送綁定Service請求，如果成功，則會調用ServiceConnection
bindService(it, conn, BIND_AUTO_CREATE);
}
private ServiceConnection conn = new ServiceConnection(){
// 綁定成功，返回的對象是IBinder接口，通過asInterface轉換為定義的ITest接口
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
Log.d(TAG, "onServiceConnected ...");
mTest = ITest.Stub.asInterface(service);
if(mTest != null){
try {
mTest.setCustomerName("chris");
Log.d(TAG, "-------------------");
Log.d(TAG, "get name = " + mTest.getCustomerName());
} catch (RemoteException e) {
e.printStackTrace();
}
}
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
}
3.5 在AndroidManifest.xml中，注冊遠程Service：
[html]
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.chris.rpc.aidl"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="10"
android:targetSdkVersion="10" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.chris.rpc.aidl.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:name="com.chris.rpc.aidl.MyService">
<intent-filter>
<action android:name="com.chris.rpc.aidl.action.MYSERVICE" />
</intent-filter>
</service>
</application>
</manifest>
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.chris.rpc.aidl"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="10"
android:targetSdkVersion="10" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.chris.rpc.aidl.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:name="com.chris.rpc.aidl.MyService">
<intent-filter>
<action android:name="com.chris.rpc.aidl.action.MYSERVICE" />
</intent-filter>
</service>
</application>
</manifest>3.6 運行截圖：
四、小結
本篇文章是讓大家了解AIDL的過程，特別是大家需要理解一個自動生成的接口類的中Stub, asInterface, onTransact方法，這些方法在Android Java Framework中有對應的實現，並最終通過native來完成。然後就是大家要了解這個遠程Service的用法就可以了。AIDL通常用在如手機播放器這類應用中，各個activity與service綁定後，可以控制播放器的各個狀態。
（之後要是有空，我會繼續寫androd java framework中關於binder的理解）
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