Android IPC 系列（1）：Service

来源：互联网发布：mac系统照片处理软件编辑：程序博客网时间：2024/06/03 17:44

原文地址：http://blog.csdn.net/chenfeng0104/article/details/6989178

使用Service的场合：

1.一个或多个Activity需要向同一应用中的Service发出执行某一操作的命令。

PS：不需要绑定

2.某个Activity需要同一应用中的Service为其单独服务，当此Activity消毁时，也将为其服务的Service一并消毁。

PS：需要绑定

3.多个Activity绑定到同一个Service，仅当所有Activity取消了绑定，Service才消毁。

PS：只有第一个Activity绑定时才调用onBind()方法，第二个、第三个....第N个直接取得第一个Activity绑定时onBind()方法返回的IBinder对象

4.即使退出当前应用时，仍希望Service继续运行（如：上传或下载任务）；或者此Service为其他应用提供服务。

PS：需要跨进程通信（IPC）

4.1当远程服务不需要支持多线程时，使用Messager.

Server端应用代码

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public class RemoteServiceProxy extends Service {
public static final int GET_RESULT = 1;
private final Messenger> new Messenger(new Handler() {
private int status = 0;
@Override
public void handleMessage(Message msg) {
if (msg.what == GET_RESULT) {
try {
msg.replyTo.send(Message.obtain(null, GET_RESULT, status++, 0));
} catch (RemoteException e) {
e.printStackTrace();
}
} else {
super.handleMessage(msg);
}
}
});
@Override
public IBinder onBind(Intent intent) {
return mMessenger.getBinder();
}
}

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<service android:name=".module.photo.RemoteServiceProxy"
android:process=":remote" />

Client端应用代码

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//开启一个服务
bindService(new Intent(this, RemoteServiceProxy.class), mConnection, BIND_AUTO_CREATE);
private Messenger mService;
private ServiceConnection> new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName> new Messenger(service);
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};

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private Messenger> new Messenger(new Handler() {
@Override
public void handleMessage(Message msg) {
if (msg.what == RemoteServiceProxy.GET_RESULT) {
Log.i("M", "From Remote Service "+msg.arg1);
} else {
super.handleMessage(msg);
}
}
});
Message message = Message.obtain(null, RemoteServiceProxy.GET_RESULT);
message.replyTo = mMessenger;
try {
mService.send(message);
} catch (RemoteException e) {
e.printStackTrace();
}

4.2当远程服务需要同时响应多个Client的请求，使用AIDL.

注意：一般我们应用中是不需要使用AIDL的，这里仅仅是为了学习和深入理解Android的IPC机制。

Server端应用代码

在Server端应用新建IRemoteService.aidl和IRemoteCallback.aidl文件，编辑内容如下

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package com.example.aidl;
interface IRemoteCallback {
void executeCallback(String msg);
}

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package com.example.aidl;
import com.example.aidl.IRemoteCallback;
interface IRemoteService {
//注册回调
void register(IRemoteCallback callback);
//取消注册回调
void unregister(IRemoteCallback callback);
//执行回调
void execute();
//获取状态
int getStatus(String flag);
}

创建Service类为客户端提供服务

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package com.example.server.service;
import com.example.aidl.IRemoteCallback;
import com.example.aidl.IRemoteService;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.RemoteCallbackList;
import android.os.RemoteException;
import android.util.Log;
public class RemoteService extends Service {
@Override
public IBinder onBind(Intent intent) {
return iBinder;
}
private final RemoteCallbackList<IRemoteCallback>> new RemoteCallbackList<IRemoteCallback>();
private IRemoteService.Stub> new IRemoteService.Stub() {
@Override
public void register(IRemoteCallback cb) throws RemoteException {
if (cb != null) remoteCallbackList.register(cb);
}
@Override
public void unregister(IRemoteCallback cb) throws RemoteException {
if (cb != null) remoteCallbackList.unregister(cb);
}
@Override
public void execute() throws RemoteException {
int size = remoteCallbackList.beginBroadcast();
while (size > 0) {
size--;
remoteCallbackList.getBroadcastItem(size).executeCallback("Hello, Client.");
}
remoteCallbackList.finishBroadcast();
Log.i("RS", "RemoteService.execute() has done.");
}
int status;
@Override
public int getStatus(String flag) throws RemoteException {
Log.i("RS", "RemoteService.getStatus(flag) flag is "+flag);
if ("reset".equals(flag))> 0;
return status++;
}
};
}

在AndroidManifast.xml中配置Service，必需设置Action过滤

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<service android:name=".server.service.RemoteService" android:process=":remote">
<intent-filter>
<action android:name="test.remote.service"/>
</intent-filter>
</service>

Client端应用代码

将Server端创建的IRemoteService.aidl和IRemoteCallback.aidl文件copy到Client端应用中

在Client端获取Server端的RemoteService对象的引用

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package com.example;
import com.example.aidl.IRemoteCallback;
import com.example.aidl.IRemoteService;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.os.RemoteException;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Toast;
public class ClientActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.client_activity);
/*
绑定远程服务，与其他进程Service通信。
注意：Client需要通过Action与RemoteService绑定，因为Client端是没有RemoteService.class的
*/
this.bindService(new Intent("test.remote.service"), sConnection, BIND_AUTO_CREATE);
this.findViewById(R.id.execute_callback).setOnClickListener(mOnClickListener);
this.findViewById(R.id.get_status).setOnClickListener(mOnClickListener);
}
private OnClickListener> new OnClickListener() {
@Override
public void onClick(View button) {
try {
if (button.getId() == R.id.execute_callback) remoteService.execute();
else {
int remoteStatus = remoteService.getStatus("set");
Toast.makeText(getApplicationContext(), "Status: "+remoteStatus+" is from RemoteService", Toast.LENGTH_LONG).show();
}
} catch (RemoteException e) {
e.printStackTrace();
}
}
};
private IRemoteService remoteService;//远程服务
private ServiceConnection> new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName>
//注册回调
try {
remoteService.register(remoteCallback);
} catch (RemoteException e) {
e.printStackTrace();
}
}
@Override
public void onServiceDisconnected(ComponentName name) {
//意外断开连接时回调
remoteService = null;
}
};
private IRemoteCallback.Stub> new IRemoteCallback.Stub() {
@Override
public void executeCallback(String msg) throws RemoteException {
Toast.makeText(getApplicationContext(), "ClientActivity: "+msg, Toast.LENGTH_LONG).show();
}
};
}

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