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Android基础--使用AIDL实现进程间的通信之复杂类型传递

2014-05-29 21:11 1001 查看

上次讲到简单的AIDL进程间通信的操作,客户端向服务端发送一个String类型的参数,服务端也返回一个String类型的结果,看似已经可以完成基本的需要了。不过在有的时候,简单的数据类型并不能满足我们的需求,我们就需要考虑怎样向服务端传递复杂的数据类型。今天就来讲一下如何向服务端传递复杂类型的问题。

首先要了解一下AIDL对Java类型的支持。

1.AIDL支持Java原始数据类型。

2.AIDL支持String和CharSequence。

3.AIDL支持传递其他AIDL接口,但你引用的每个AIDL接口都需要一个import语句,即使位于同一个包中。

4.AIDL支持传递实现了android.os.Parcelable接口的复杂类型,同样在引用这些类型时也需要import语句。(Parcelable接口告诉Android运行时在封送(marshalling)和解封送(unmarshalling)过程中实现如何序列化和反序列化对象,你可以很容易联想到java.io.Serializable接口。有些朋友可能会有疑问,两种接口功能确实类似,但为什么Android不用内置的Java序列化机制,而偏偏要搞一套新东西呢?这是因为Android团队认为Java中的序列化太慢,难以满足Android的进程间通信需求,所以他们构建了Parcelable解决方案。Parcelable要求显示序列化类的成员,但最终序列化对象的速度将快很多。另外要注意的是,Android提供了两种机制来将数据传递给另一个进程,第一种是使用Intent将数据束(Bundle)传递给活动,第二种也就是Parcelable传递给服务。这两种机制不可互换,不要混淆。也就是说,Parcelable无法传递给活动,只能用作AIDL定义的一部分)。

5.AIDL支持java.util.List和java.util.Map,但是有一些限制。集合中项的允许数据类型包括Java原始类型、String、CharSequence或是android.os.Parcelable。无需为List和Map提供import语句,但需要为Parcelable提供import语句。

6.非原始类型中,除了String和CharSequence以外,其余均需要一个方向指示符。方向指示符包括in、out、和inout。in表示由客户端设置,out表示由服务端设置,inout表示客户端和服务端都设置了该值。

接下来就演示一下具体的流程:

我们先看一下服务端的结构:



其中,Person类是我们要在服务端和客户端中间进行传递的类型,代码如下:

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package com.scott.aidl; import android.os.Parcel; import android.os.Parcelable; public class Person implements Parcelable { private String name; private int sex; //必须提供一个名为CREATOR的static final属性 该属性需要实现android.os.Parcelable.Creator<T>接口 public static final Parcelable.Creator<Person> CREATOR = new Parcelable.Creator<Person>() { @Override public Person createFromParcel(Parcel source) { return new Person(source); } @Override public Person[] newArray(int size) { return new Person[size]; } }; public Person() { } private Person(Parcel source) { readFromParcel(source); } @Override public int describeContents() { return 0; } //注意写入变量和读取变量的顺序应该一致 不然得不到正确的结果 @Override public void writeToParcel(Parcel dest, int flags) { dest.writeString(name); dest.writeInt(sex); } //注意读取变量和写入变量的顺序应该一致 不然得不到正确的结果 public void readFromParcel(Parcel source) { name = source.readString(); sex = source.readInt(); } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getSex() { return sex; } public void setSex(int sex) { this.sex = sex; } }
package com.scott.aidl;

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

public class Person implements Parcelable {

private String name;
private int sex;

//必须提供一个名为CREATOR的static final属性 该属性需要实现android.os.Parcelable.Creator<T>接口
public static final Parcelable.Creator<Person> CREATOR = new Parcelable.Creator<Person>() {

@Override
public Person createFromParcel(Parcel source) {
return new Person(source);
}

@Override
public Person[] newArray(int size) {
return new Person[size];
}
};

public Person() {

}

private Person(Parcel source) {
readFromParcel(source);
}

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

//注意写入变量和读取变量的顺序应该一致 不然得不到正确的结果
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(name);
dest.writeInt(sex);
}

//注意读取变量和写入变量的顺序应该一致 不然得不到正确的结果
public void readFromParcel(Parcel source) {
name = source.readString();
sex = source.readInt();
}

public String getName() {
return name;
}

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

public int getSex() {
return sex;
}

public void setSex(int sex) {
this.sex = sex;
}

}


然后我们需要在同一包下建立一个与包含复杂类型的Person.java文件匹配的Person.aidl文件,代码如下:

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package com.scott.aidl; parcelable Person;

package com.scott.aidl;
parcelable Person;


这个Person.aidl文件很简单,就是定义了一个Parcelable类,告诉系统我们需要序列化和反序列化的类型。每一个实现了Parcelable的类型都需要对应的.aidl文件。AIDL编译器在编译AIDL文件时会自动查找此类文件。

接下来,我们需要创建一个IGreetService.aidl文件,以接收类型为Person的输入参数,以便客户端可以将Person传递给服务。

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package com.scott.aidl;
import com.scott.aidl.Person;

interface IGreetService {
String greet(in Person person);
}

package com.scott.aidl;
import com.scott.aidl.Person;

interface IGreetService {
String greet(in Person person);
}


注意,我们需要在参数上加入方向指示符in,代表参数由客户端设置,我们还需要为Person提供一个import语句(虽然说在同一个包下)。

此时,在eclipse插件的帮助下,AIDL编译器会自动编译生成一个IGreetService.java文件,格式化后的代码如下:

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package com.scott.aidl;

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

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

/**
* Cast an IBinder object into an com.scott.aidl.IGreetService
* interface, generating a proxy if needed.
*/
public static com.scott.aidl.IGreetService 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.scott.aidl.IGreetService))) {
return ((com.scott.aidl.IGreetService) iin);
}
return new com.scott.aidl.IGreetService.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_greet: {
data.enforceInterface(DESCRIPTOR);
com.scott.aidl.Person _arg0;
if ((0 != data.readInt())) {
_arg0 = com.scott.aidl.Person.CREATOR.createFromParcel(data);
} else {
_arg0 = null;
}
java.lang.String _result = this.greet(_arg0);
reply.writeNoException();
reply.writeString(_result);
return true;
}
}
return super.onTransact(code, data, reply, flags);
}

private static class Proxy implements com.scott.aidl.IGreetService {
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 java.lang.String greet(com.scott.aidl.Person person) 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);
if ((person != null)) {
_data.writeInt(1);
person.writeToParcel(_data, 0);
} else {
_data.writeInt(0);
}
mRemote.transact(Stub.TRANSACTION_greet, _data, _reply, 0);
_reply.readException();
_result = _reply.readString();
} finally {
_reply.recycle();
_data.recycle();
}
return _result;
}
}

static final int TRANSACTION_greet = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
}

public java.lang.String greet(com.scott.aidl.Person person) throws android.os.RemoteException;
}

package com.scott.aidl;

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

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

/**
* Cast an IBinder object into an com.scott.aidl.IGreetService
* interface, generating a proxy if needed.
*/
public static com.scott.aidl.IGreetService 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.scott.aidl.IGreetService))) {
return ((com.scott.aidl.IGreetService) iin);
}
return new com.scott.aidl.IGreetService.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_greet: {
data.enforceInterface(DESCRIPTOR);
com.scott.aidl.Person _arg0;
if ((0 != data.readInt())) {
_arg0 = com.scott.aidl.Person.CREATOR.createFromParcel(data);
} else {
_arg0 = null;
}
java.lang.String _result = this.greet(_arg0);
reply.writeNoException();
reply.writeString(_result);
return true;
}
}
return super.onTransact(code, data, reply, flags);
}

private static class Proxy implements com.scott.aidl.IGreetService {
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 java.lang.String greet(com.scott.aidl.Person person) 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);
if ((person != null)) {
_data.writeInt(1);
person.writeToParcel(_data, 0);
} else {
_data.writeInt(0);
}
mRemote.transact(Stub.TRANSACTION_greet, _data, _reply, 0);
_reply.readException();
_result = _reply.readString();
} finally {
_reply.recycle();
_data.recycle();
}
return _result;
}
}

static final int TRANSACTION_greet = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
}

public java.lang.String greet(com.scott.aidl.Person person) throws android.os.RemoteException;
}


该文件的大纲视图如下:



接下来,就该完成我们的AIDLService逻辑部分了,AIDLService.java代码如下:

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package com.scott.server;

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

import com.scott.aidl.IGreetService;
import com.scott.aidl.Person;

public class AIDLService extends Service {

private static final String TAG = "AIDLService";

IGreetService.Stub stub = new IGreetService.Stub() {
@Override
public String greet(Person person) throws RemoteException {
Log.i(TAG, "greet(Person person) called");

String greeting = "hello, " + person.getName();
switch (person.getSex()) {
case 0:
greeting = greeting + ", you're handsome.";
break;
case 1:
greeting = greeting + ", you're beautiful.";
break;
}
return greeting;
}
};

@Override
public IBinder onBind(Intent intent) {
Log.i(TAG, "onBind() called");
return stub;
}

@Override
public boolean onUnbind(Intent intent) {
Log.i(TAG, "onUnbind() called");
return true;
}

@Override
public void onDestroy() {
super.onDestroy();
Log.i(TAG, "onDestroy() called");
}
}

package com.scott.server;

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

import com.scott.aidl.IGreetService;
import com.scott.aidl.Person;

public class AIDLService extends Service {

private static final String TAG = "AIDLService";

IGreetService.Stub stub = new IGreetService.Stub() {
@Override
public String greet(Person person) throws RemoteException {
Log.i(TAG, "greet(Person person) called");

String greeting = "hello, " + person.getName();
switch (person.getSex()) {
case 0:
greeting = greeting + ", you're handsome.";
break;
case 1:
greeting = greeting + ", you're beautiful.";
break;
}
return greeting;
}
};

@Override
public IBinder onBind(Intent intent) {
Log.i(TAG, "onBind() called");
return stub;
}

@Override
public boolean onUnbind(Intent intent) {
Log.i(TAG, "onUnbind() called");
return true;
}

@Override
public void onDestroy() {
super.onDestroy();
Log.i(TAG, "onDestroy() called");
}
}


最后,在AndroidManifest.xml中配置该服务:

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<service android:name=".AIDLService"> <intent-filter> <action android:name="android.intent.action.AIDLService" /> <category android:name="android.intent.category.DEFAULT" /> </intent-filter> </service>

<service android:name=".AIDLService">
<intent-filter>
<action android:name="android.intent.action.AIDLService" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</service>


服务端就已经完成了。接下来我们来看一下客户端的结构:



我们需要把服务端的Person.java、Person.aidl和IGreetService.aidl拷到对应的包下。我们主要来看看MainActivity.java代码:

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package com.scott.client; 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.Toast; import com.scott.aidl.IGreetService; import com.scott.aidl.Person; public class MainActivity extends Activity { private Button bindBtn; private Button greetBtn; private Button unbindBtn; private IGreetService greetService; private ServiceConnection conn = new ServiceConnection() { @Override public void onServiceConnected(ComponentName name, IBinder service) { Log.i("ServiceConnection", "onServiceConnected() called"); greetService = IGreetService.Stub.asInterface(service); } @Override public void onServiceDisconnected(ComponentName name) { //This is called when the connection with the service has been unexpectedly disconnected, //that is, its process crashed. Because it is running in our same process, we should never see this happen. Log.i("ServiceConnection", "onServiceDisconnected() called"); } }; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); bindBtn = (Button) findViewById(R.id.bindBtn); bindBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent intent = new Intent("android.intent.action.AIDLService"); bindService(intent, conn, Context.BIND_AUTO_CREATE); bindBtn.setEnabled(false); greetBtn.setEnabled(true); unbindBtn.setEnabled(true); } }); greetBtn = (Button) findViewById(R.id.greetBtn); greetBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { try { Person person = new Person(); person.setName("scott"); person.setSex(0); String retVal = greetService.greet(person); Toast.makeText(MainActivity.this, retVal, Toast.LENGTH_SHORT).show(); } catch (RemoteException e) { Toast.makeText(MainActivity.this, "error", Toast.LENGTH_SHORT).show(); } } }); unbindBtn = (Button) findViewById(R.id.unbindBtn); unbindBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { unbindService(conn); bindBtn.setEnabled(true); greetBtn.setEnabled(false); unbindBtn.setEnabled(false); } }); } }

package com.scott.client;

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.Toast;

import com.scott.aidl.IGreetService;
import com.scott.aidl.Person;

public class MainActivity extends Activity {

private Button bindBtn;
private Button greetBtn;
private Button unbindBtn;

private IGreetService greetService;
private ServiceConnection conn = new ServiceConnection() {

@Override
public void onServiceConnected(ComponentName name, IBinder service) {
Log.i("ServiceConnection", "onServiceConnected() called");
greetService = IGreetService.Stub.asInterface(service);
}

@Override
public void onServiceDisconnected(ComponentName name) {
//This is called when the connection with the service has been unexpectedly disconnected,
//that is, its process crashed. Because it is running in our same process, we should never see this happen.
Log.i("ServiceConnection", "onServiceDisconnected() called");
}
};

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

bindBtn = (Button) findViewById(R.id.bindBtn);
bindBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent("android.intent.action.AIDLService");
bindService(intent, conn, Context.BIND_AUTO_CREATE);

bindBtn.setEnabled(false);
greetBtn.setEnabled(true);
unbindBtn.setEnabled(true);
}
});

greetBtn = (Button) findViewById(R.id.greetBtn);
greetBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {
Person person = new Person();
person.setName("scott");
person.setSex(0);
String retVal = greetService.greet(person);
Toast.makeText(MainActivity.this, retVal, Toast.LENGTH_SHORT).show();
} catch (RemoteException e) {
Toast.makeText(MainActivity.this, "error", Toast.LENGTH_SHORT).show();
}
}
});

unbindBtn = (Button) findViewById(R.id.unbindBtn);
unbindBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
unbindService(conn);

bindBtn.setEnabled(true);
greetBtn.setEnabled(false);
unbindBtn.setEnabled(false);
}
});
}
}


通过这种方式,就可以将Person类型的对象传递到服务端,实现复杂类型的通信传递。

当点击greetBtn时,截图如下:



然后看一下整个过程的日志信息。点击bindBtn、greetBtn、unbindBtn的整个过程日志如下:

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