本文提供了一个关于AIDL使用的简单易懂的例子,分为客户端和服务端两部分,分别为客户端和服务端新建一个eclipse工程,实现了从客户端向服务端发送请求,服务端打印log的功能。
我的理解: 进程间的通信 ,让服务器作出反应(大概就是这个意思)
客户端和服务端的源码结构如下:
注意,由于客户端和服务端的aidl文件所在包名必须一样,而两个包名一样的程序在安装时会产生冲突,所以这里用了一个技巧,在客户端工程的AndroidManifest.xml里把包名指定为com.styleflying,所以大家就会看到gen目录下的R.java所在的包是com.styleflying而不是com.styleflying.AIDL
正文
现在客户端和服务端工程分别新建一个aidl接口,所在包和文件名必须一样。两个aidl接口是一样的,内容如下:
[java] view plain copy
1. package com.styleflying.AIDL;
2. interface mInterface{
3. void invokTest();
4. }
自动编译生成.java文件如下:
[java] view plain copy
1. /*
2. * This file is auto-generated. DO NOT MODIFY.
3. * Original file: G://workspace//AidlDemo_client//src//com//styleflying//AIDL//mInterface.aidl
4. */
5. package com.styleflying.AIDL;
6. public interface mInterface extends android.os.IInterface
7. {
8. /** Local-side IPC implementation stub class. */
9. public static abstract class Stub extends android.os.Binder implements com.styleflying.AIDL.mInterface
10. {
11. private static final java.lang.String DESCRIPTOR = "com.styleflying.AIDL.mInterface";
12. /** Construct the stub at attach it to the interface. */
13. public Stub()
14. {
15. this.attachInterface(this, DESCRIPTOR);
16. }
17. /**
18. * Cast an IBinder object into an com.styleflying.AIDL.mInterface interface,
19. * generating a proxy if needed.
20. */
21. public static com.styleflying.AIDL.mInterface asInterface(android.os.IBinder obj)
22. {
23. if ((obj==null)) {
24. return null;
25. }
26. android.os.IInterface iin = (android.os.IInterface)obj.queryLocalInterface(DESCRIPTOR);
27. if (((iin!=null)&&(iin instanceof com.styleflying.AIDL.mInterface))) {
28. return ((com.styleflying.AIDL.mInterface)iin);
29. }
30. return new com.styleflying.AIDL.mInterface.Stub.Proxy(obj);
31. }
32. public android.os.IBinder asBinder()
33. {
34. return this;
35. }
36. @Override public boolean onTransact(int code, android.os.Parcel data, android.os.Parcel reply, int flags) throws android.os.RemoteException
37. {
38. switch (code)
39. {
40. case INTERFACE_TRANSACTION:
41. {
42. reply.writeString(DESCRIPTOR);
43. return true;
44. }
45. case TRANSACTION_invokTest:
46. {
47. data.enforceInterface(DESCRIPTOR);
48. this.invokTest();
49. reply.writeNoException();
50. return true;
51. }
52. }
53. return super.onTransact(code, data, reply, flags);
54. }
55. private static class Proxy implements com.styleflying.AIDL.mInterface
56. {
57. private android.os.IBinder mRemote;
58. Proxy(android.os.IBinder remote)
59. {
60. mRemote = remote;
61. }
62. public android.os.IBinder asBinder()
63. {
64. return mRemote;
65. }
66. public java.lang.String getInterfaceDescriptor()
67. {
68. return DESCRIPTOR;
69. }
70. public void invokTest() throws android.os.RemoteException
71. {
72. android.os.Parcel _data = android.os.Parcel.obtain();
73. android.os.Parcel _reply = android.os.Parcel.obtain();
74. try {
75. _data.writeInterfaceToken(DESCRIPTOR);
76. 0);
77. _reply.readException();
78. }
79. finally {
80. _reply.recycle();
81. _data.recycle();
82. }
83. }
84. }
85. static final int TRANSACTION_invokTest = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
86. }
87. public void invokTest() throws android.os.RemoteException;
88. }
客户端的mAIDLActivity.java如下:
[java] view plain copy
1. package com.styleflying.AIDL;
2. import android.app.Activity;
3. import android.content.ComponentName;
4. import android.content.Context;
5. import android.content.Intent;
6. import android.content.ServiceConnection;
7. import android.os.Bundle;
8. import android.os.IBinder;
9. import android.os.RemoteException;
10. import android.util.Log;
11. import android.view.View;
12. import android.view.View.OnClickListener;
13. import android.widget.Button;
14. import android.widget.Toast;
15. import com.styleflying.R;
16. public class mAIDLActivity extends Activity {
17.
18. private static final String TAG = "AIDLActivity";
19. private Button btnOk;
20. private Button btnCancel;
21. private Button btnCallBack;
22.
23. private void Log(String str){
24. "----------" + str + "----------");
25. }
26.
27.
28. mInterface mService;
29. private ServiceConnection mConnection = new ServiceConnection(){
30. public void onServiceConnected(ComponentName className,
31. IBinder service){
32. "connect service");
33. mService = mInterface.Stub.asInterface(service);
34. }
35.
36. public void onServiceDisconnected(ComponentName className){
37. "disconnect service");
38. null;
39. }
40. };
41.
42.
43.
44. /** Called when the activity is first created. */
45. @Override
46. public void onCreate(Bundle savedInstanceState) {
47. super.onCreate(savedInstanceState);
48. setContentView(R.layout.main);
49.
50. btnOk = (Button)findViewById(R.id.btn_ok);
51. btnCancel = (Button)findViewById(R.id.btn_cancel);
52. btnCallBack = (Button)findViewById(R.id.btn_callback);
53.
54. new OnClickListener(){
55. public void onClick(View v){
56. new Bundle();
57. new Intent("com.styleflying.AIDL.service");
58. intent.putExtras(args);
59. bindService(intent,mConnection,Context.BIND_AUTO_CREATE);
60. }
61. });
62.
63. new OnClickListener(){
64. public void onClick(View v){
65. unbindService(mConnection);
66. }
67. });
68. new OnClickListener(){
69. public void onClick(View v){
70. try{
71. "current Thread id = " + Thread.currentThread().getId());
72. mService.invokTest();
73. }
74. catch(RemoteException e){
75.
76. }
77. }
78. });
79.
80.
81. }
82. }
客户端在执行bindService的时候,成功绑定服务之后,会回调mConnection的onServiceConnected(),并且传回了服务端的通信接口IBinder,此IBinder即服务onBind()时返回的IBinder,详见mAIDLService.java。
在onServiceConnected(),客户端成功获取了服务端通信接口,实际上是本地代理对象,该对象存在于客户端进程空间,客户端只和代理对象交互,真正的IPC通信是本地代理对象和服务端的通信。
mAIDLService.java如下:
[c-sharp] view plain copy
1. package com.styleflying.AIDL;
2. import android.app.Service;
3. import android.content.Intent;
4. import android.os.IBinder;
5. import android.os.Looper;
6. import android.os.RemoteException;
7. import android.util.Log;
8. import android.widget.Toast;
9. public class mAIDLService extends Service{
10. private static final String TAG = "AIDLService";
11.
12. private void Log(String str){
13. "----------" + str + "----------");
14. }
15.
16. public void onCreate(){
17. "service created");
18. }
19.
20. public void onStart(Intent intent, int startId){
21. "service started id = " + startId);
22. }
23.
24. public IBinder onBind(Intent t){
25. "service on bind");
26. return mBinder;
27. }
28.
29. public void onDestroy(){
30. "service on destroy");
31. super.onDestroy();
32. }
33.
34. public boolean onUnbind(Intent intent){
35. "service on unbind");
36. return super.onUnbind(intent);
37. }
38.
39. public void onRebind(Intent intent){
40. "service on rebind");
41. super.onRebind(intent);
42. }
43.
44.
45. private final mInterface.Stub mBinder = new mInterface.Stub() {
46. public void invokTest() throws RemoteException {
47. // TODO Auto-generated method stub
48. "remote call from client! current thread id = " + Thread.currentThread().getId());
49. }
50. };
51. }
注意onBind()函数,返回了mBinder,而mBinder实现了mInterface.Stub,实现了mInterface接口,执行了打印log的操作。
整个交互流程如下:
1.客户端通过绑定服务,获取了服务的句柄(本地代理对象);
2.客户端执行onClick(),调用本地代理对象的invokTest()函数,本地代理对象调用mRemote.transact()发出远程调用请求(见 mInterface.java);
3.服务端响应onTransact()执行this.invokTest(),并将执行结果返回;
由于客户端只和本地代理对象即服务句柄通信,由代理对象进行真正的IPC操作,所以对客户端来说,IPC过程是透明的,调用远程操作如同调用本地操作一样。在客户端调用transact()时,会将服务描述DSCRIPTION写入到data里,在客户端onTransact时会验证,如果两个不一样,则不能通信。而DSCRIPTION是根据mInterface包名和接口名自动生成的,这就是为什么两个工程里的mInterface.aidl要在同一个包的原因。
在这个过程中,mInterface.aidl起到了桥梁的作用,规定统一了客户端和服务端的通信接口,使得客户端和服务端得以成功的通信。
具体的通信transact和onTransact的过程也就是利用Binder驱动通信的过程,在这里就不多叙述。
最后补上两个工程的AndroidManifest.xml
[xhtml] view plain copy
1. <?xml version="1.0" encoding="utf-8"?>
2. <manifest xmlns:android="http://schemas.android.com/apk/res/android"
3. package="com.styleflying"
4. android:versionCode="1"
5. android:versionName="1.0">
6. <application android:icon="@drawable/icon" android:label="@string/app_name">
7. <activity android:name=".AIDL.mAIDLActivity"
8. android:label="@string/app_name">
9. <intent-filter>
10. <action android:name="android.intent.action.MAIN" />
11. <category android:name="android.intent.category.LAUNCHER" />
12. </intent-filter>
13. </activity>
14. </application>
15. <uses-sdk android:minSdkVersion="8" />
16. </manifest>
[xhtml] view plain copy
1. <?xml version="1.0" encoding="utf-8"?>
2. <manifest xmlns:android="http://schemas.android.com/apk/res/android"
3. package="com.styleflying.AIDL"
4. android:versionCode="1"
5. android:versionName="1.0">
6. <application android:icon="@drawable/icon" android:label="@string/app_name">
7. <service android:name=".mAIDLService">
8. <intent-filter>
9. <action android:name="com.styleflying.AIDL.service" />
10. <category android:name="android.intent.category.DEFAULT" />
11. </intent-filter>
12. </service>
13. </application>
14. <uses-sdk android:minSdkVersion="8" />
15. </manifest>