Android Inter-App Communication

이번 튜토리얼에서는 두 개의 Process 사이에서  하나가 다른 Process의 Service을 호출하는 방법에 대하여 설명하고 있습니다.

본 문서에서는 다음 내용을 다룹니다.

• Invocation Handler을 작성하는 방법

• Remote Service을 Bind 하는 방법

• Invocation을 호출한 Process에게 Value Return 하는 방법

Step 1: Create the Service

Invocation될 Service을 만듭니다. Service에는반드시 IBinder 객체를 Return하는 onBind Method을 Override해야 합니다.

Service에서는 Messenger 컴포넌트를 사용합니다. 이 Messenger 컴포넌트는 내부 Process 간 Communication 이 가능하게 해줍니다.

public class RemoteService extends Service { private Messenger messenger; //receives remote invocations @Override public IBinder onBind(Intent intent) { if(this.messenger == null) { synchronized(RemoteService.class) { if(this.messenger == null) { this.messenger = new Messenger(new IncomingHandler()); } } } //Return the proper IBinder instance return this.messenger.getBinder(); }

Step 2: Implement the Handler

Handler는 Messenger을 등록할수 있는 컴포넌트 입니다. 이 컴포넌트는 Remote Invocation을 받을 수 있는 컴포너트 중 하나 입니다.

Handler는 들어온 요청의 Messenger에 따라 요청을 처리하고 응답을 보내게 되어있습니다.

private class IncomingHandler extends Handler { @Override                public void handleMessage(Message msg) { System.out.println("*****************************************"); System.out.println("Remote Service successfully invoked!!!!!!"); System.out.println("*****************************************"); int what = msg.what; Toast.makeText(RemoteService.this.getApplicationContext(), "Remote Service invoked-("+what+")", Toast.LENGTH_LONG).show(); //Setup the reply message Message message = Message.obtain(null, 2, 0, 0); try { //make the RPC invocation Messenger replyTo = msg.replyTo; replyTo.send(message); } catch(RemoteException rme) { //Show an Error Message Toast.makeText(RemoteService.this, "Invocation Failed!!", Toast.LENGTH_LONG).show(); }    } }

아래는 RemoterService Application의 Full Source입니다.

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"      package="org.openmobster.remote.service.android.app"      android:versionCode="1"      android:versionName="1.0">    <application android:label="@string/app_name" android:icon="@drawable/icon">        <activity android:name="org.openmobster.app.MainActivity"                  android:label="@string/app_name">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>            <intent-filter>                <action android:name="android.intent.action.VIEW" />            </intent-filter>        </activity>                <service android:name="org.openmobster.app.RemoteService" android:exported="true">        </service>    </application>    <uses-permission android:name="android.permission.INTERNET" /> </manifest>

“org.openmobster.app.MainActivity”는 Hello world 수준으로 만들어 줍니다.

RemoteService

package org.openmobster.app; import android.app.Service; import android.content.Intent; import android.os.IBinder; import android.os.Handler; import android.os.Message; import android.os.Messenger; import android.os.RemoteException; import android.widget.Toast; public class RemoteService extends Service { private Messenger messenger; //receives remote invocations @Override public IBinder onBind(Intent intent) { if(this.messenger == null) { synchronized(RemoteService.class) { if(this.messenger == null) { this.messenger = new Messenger(new IncomingHandler()); } } } //Return the proper IBinder instance return this.messenger.getBinder(); } private class IncomingHandler extends Handler { @Override        public void handleMessage(Message msg) { System.out.println("*****************************************"); System.out.println("Remote Service successfully invoked!!!!!!"); System.out.println("*****************************************"); int what = msg.what; Toast.makeText(RemoteService.this.getApplicationContext(), "Remote Service invoked-("+what+")", Toast.LENGTH_LONG).show(); //Setup the reply message Message message = Message.obtain(null, 2, 0, 0); try { //make the RPC invocation Messenger replyTo = msg.replyTo; replyTo.send(message); } catch(RemoteException rme) { //Show an Error Message Toast.makeText(RemoteService.this, "Invocation Failed!!", Toast.LENGTH_LONG).show(); }        } } }

Step 3: Create a Client ServiceConnection Object

Client가 Service에 바인딩하는 경우 이 호출은 비동기 방식입니다. 시스템은 클라이언트에게 ServiceConnection 같은 Callback 메커니즘을 제공하고 있습니다.

클라이언트는 제공된 IBinder 인스턴스를 사용하여 Messenger 객체를 설정합니다.

private class RemoteServiceConnection implements ServiceConnection { @Override public void onServiceConnected(ComponentName component, IBinder binder) { MainActivity.this.messenger = new Messenger(binder); MainActivity.this.isBound = true; } @Override public void onServiceDisconnected(ComponentName component) { MainActivity.this.messenger = null; MainActivity.this.isBound = false; } }

Step 4: Bind to the Remote Service

Intent을 생성하고 Invoke될 Service을 가리키는 ClassName을 지정합니다.

@Override protected void onStart() { super.onStart(); //Bind to the remote service Intent intent = new Intent(); intent.setClassName("org.openmobster.remote.service.android.app", "org.openmobster.app.RemoteService"); this.bindService(intent, this.connection, Context.BIND_AUTO_CREATE); }

Step 5: Make the Remote Invocation

Message.obtain을 이용하여 Message 객체를 생성합니다. message.replyTo에 Local Messenger를 담습니다. Messenger에 Message을 담아 Send합니다.

//Setup the message for invocation Message message = Message.obtain(null, 1, 0, 0); try { //Set the ReplyTo Messenger for processing the invocation response message.replyTo = MainActivity.this.replyTo; //Make the invocation MainActivity.this.messenger.send(message); } catch(RemoteException rme) { //Show an Error Message Toast.makeText(MainActivity.this, "Invocation Failed!!", Toast.LENGTH_LONG).show(); }

아래는 RemoteClient Full Source입니다.

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"      package="org.openmobster.app"      android:versionCode="1"      android:versionName="1.0">    <application android:label="@string/app_name" android:icon="@drawable/icon">        <activity android:name=".MainActivity"                  android:label="@string/app_name">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>            <intent-filter>                <action android:name="android.intent.action.VIEW" />            </intent-filter>        </activity>    </application>    <uses-permission android:name="android.permission.INTERNET" /> </manifest>

/layout/main.xml

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <Button android:id="@+id/invoke"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="Invoke Remote Service" />                                                                            </LinearLayout>

MainActivity

package org.openmobster.app; import java.lang.reflect.Field; 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.Handler; import android.os.IBinder; import android.os.Message; import android.os.Messenger; import android.os.RemoteException; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.Toast; public class MainActivity extends Activity { private Messenger messenger = null; //used to make an RPC invocation private boolean isBound = false; private ServiceConnection connection;//receives callbacks from bind and unbind invocations private Messenger replyTo = null; //invocation replies are processed by this Messenger public MainActivity() { } @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); this.connection = new RemoteServiceConnection(); this.replyTo = new Messenger(new IncomingHandler()); } @Override protected void onStart() { super.onStart(); //Bind to the remote service Intent intent = new Intent(); intent.setClassName("org.openmobster.remote.service.android.app", "org.openmobster.app.RemoteService"); this.bindService(intent, this.connection, Context.BIND_AUTO_CREATE); } @Override protected void onStop() { super.onStop(); //Unbind if it is bound to the service if(this.isBound) { this.unbindService(connection); this.isBound = false; } } @Override protected void onResume() { try { super.onResume(); //render the main screen String layoutClass = this.getPackageName()+".R$layout"; String main = "main"; Class clazz = Class.forName(layoutClass); Field field = clazz.getField(main); int screenId = field.getInt(clazz); this.setContentView(screenId); //Invoke Remote button Button invokeButton = (Button)findViewById(R.id.invoke); invokeButton.setOnClickListener(new onClickListener(){ @Override public void onClick(View button) { if(MainActivity.this.isBound) { //Setup the message for invocation Message message = Message.obtain(null, 1, 0, 0); try { //Set the ReplyTo Messenger for processing the invocation response message.replyTo = MainActivity.this.replyTo; //Make the invocation MainActivity.this.messenger.send(message); } catch(RemoteException rme) { //Show an Error Message Toast.makeText(MainActivity.this, "Invocation Failed!!", Toast.LENGTH_LONG).show(); } } else { Toast.makeText(MainActivity.this, "Service is Not Bound!!", Toast.LENGTH_LONG).show(); } }  } ); } catch(Exception e) { e.printStackTrace(System.out); } } private class RemoteServiceConnection implements ServiceConnection { @Override public void onServiceConnected(ComponentName component, IBinder binder) { MainActivity.this.messenger = new Messenger(binder); MainActivity.this.isBound = true; } @Override public void onServiceDisconnected(ComponentName component) { MainActivity.this.messenger = null; MainActivity.this.isBound = false; } } private class IncomingHandler extends Handler { @Override        public void handleMessage(Message msg) { System.out.println("*****************************************"); System.out.println("Return successfully received!!!!!!"); System.out.println("*****************************************"); int what = msg.what; Toast.makeText(MainActivity.this.getApplicationContext(), "Remote Service replied-("+what+")", Toast.LENGTH_LONG).show();        } } }