ANDROID: Services

Service Layanan adalah komponen yang berjalan di background untuk melakukan operasi yang berjalan lama tanpa perlu berinteraksi dengan pengguna dan berfungsi bahkan jika aplikasi destroyed. Sebuah service pada dasarnya ada dua state

State dari Service
Sr.No.	State	Description
1	Started	A service is started when an application component, such as an activity, starts it by calling startService(). Once started, a service can run in the background indefinitely, even if the component that started it is destroyed.
2	Bound	A service is bound when an application component binds to it by calling bindService(). A bound service offers a client-server interface that allows components to interact with the service, send requests, get results, and even do so across processes with interprocess communication (IPC).

A service has life cycle callback methods that you can implement to monitor changes in the service's state and you can perform work at the appropriate stage. The following diagram on the left shows the life cycle when the service is created with startService() and the diagram on the right shows the life cycle when the service is created with bindService(): (image courtesy : android.com )

Service memiliki method callback life cycle yang dapat kita terapkan untuk memantau perubahan dalam status service dan kita dapat melakukan pekerjaan pada tahap yang sesuai. Diagram di sebelah kiri berikut menunjukkan life cycle saat service dibuat dengan startService() dan diagram di sebelah kanan menunjukkan siklus hidup saat layanan dibuat dengan bindService(): (gambar milik: android.com )

Android Service lifecycle

To create an service, you create a Java class that extends the Service base class or one of its existing subclasses. The Service base class defines various callback methods and the most important are given below. You don't need to implement all the callbacks methods. However, it's important that you understand each one and implement those that ensure your app behaves the way users expect.

Untuk membuat layanan, Anda membuat kelas Java yang memperluas kelas dasar Layanan atau salah satu subkelasnya yang sudah ada. Kelas dasar Layanan mendefinisikan berbagai metode panggilan balik dan yang paling penting diberikan di bawah ini. Anda tidak perlu menerapkan semua metode callback. Namun, penting bagi Anda untuk memahami masing-masing dan menerapkannya yang memastikan aplikasi Anda berperilaku seperti yang diharapkan pengguna.

Caption text
Sr.No.	Callback	Description
1	onStartCommand()	The system calls this method when another component, such as an activity, requests that the service be started, by calling startService(). If you implement this method, it is your responsibility to stop the service when its work is done, by calling stopSelf() or stopService() methods.
2	onBind()	The system calls this method when another component wants to bind with the service by calling bindService(). If you implement this method, you must provide an interface that clients use to communicate with the service, by returning an IBinder object. You must always implement this method, but if you don't want to allow binding, then you should return null.
3	onUnbind()	The system calls this method when all clients have disconnected from a particular interface published by the service.
4	onRebind()	The system calls this method when new clients have connected to the service, after it had previously been notified that all had disconnected in its onUnbind(Intent).
5	onCreate()	The system calls this method when the service is first created using onStartCommand() or onBind(). This call is required to perform one-time set-up.
6	onDestroy()	The system calls this method when the service is no longer used and is being destroyed. Your service should implement this to clean up any resources such as threads, registered listeners, receivers, etc.

The following skeleton service demonstrates each of the life cycle methods −

Layanan kerangka berikut menunjukkan masing-masing metode siklus hidup

package com.tutorialspoint;

import android.app.Service;
import android.os.IBinder;
import android.content.Intent;
import android.os.Bundle;

public class HelloService extends Service {
   
   /** indicates how to behave if the service is killed */
   int mStartMode;
   
   /** interface for clients that bind */
   IBinder mBinder;     
   
   /** indicates whether onRebind should be used */
   boolean mAllowRebind;  

   /** Called when the service is being created. */
   @Override
   public void onCreate() {
     
   } 

   /** The service is starting, due to a call to startService() */
   @Override
   public int onStartCommand(Intent intent, int flags, int startId) {
      return mStartMode;
   } 

   /** A client is binding to the service with bindService() */
   @Override
   public IBinder onBind(Intent intent) {
      return mBinder;
   } 

   /** Called when all clients have unbound with unbindService() */
   @Override
   public boolean onUnbind(Intent intent) {
      return mAllowRebind;
   }

   /** Called when a client is binding to the service with bindService()*/
   @Override
   public void onRebind(Intent intent) {

   }

   /** Called when The service is no longer used and is being destroyed */
   @Override
   public void onDestroy() {

   }
}

Example

This example will take you through simple steps to show how to create your own Android Service. Follow the following steps to modify the Android application we created in Hello World Example chapter −

Contoh ini akan membawa Anda melalui langkah-langkah sederhana untuk menunjukkan cara membuat Layanan Android Anda sendiri. Ikuti langkah-langkah berikut untuk memodifikasi aplikasi Android yang kami buat di bab Contoh Hello World

Step Android Aplikasi
Step	Description
1	You will use Android StudioIDE to create an Android application and name it as My Application under a package com.example.tutorialspoint7.myapplication as explained in the Hello World Example chapter.
2	Modify main activity file MainActivity.java to add startService() and stopService() methods.
3	Create a new java file MyService.java under the package com.example.My Application. This file will have implementation of Android service related methods.
4	Define your service in AndroidManifest.xml file using <service.../> tag. An application can have one or more services without any restrictions.
5	Modify the default content of res/layout/activity_main.xml file to include two buttons in linear layout.
6	No need to change any constants in res/values/strings.xml file. Android studio take care of string values
7	Run the application to launch Android emulator and verify the result of the changes done in the application.

Following is the content of the modified main activity file MainActivity.java. This file can include each of the fundamental life cycle methods. We have added startService() and stopService() methods to start and stop the service.

Berikut adalah isi dari file aktivitas utama MainActivity.java yang dimodifikasi. File ini dapat menyertakan setiap metode siklus hidup dasar. Kami telah menambahkan metode startService() dan stopService() untuk memulai dan menghentikan layanan.

package com.example.tutorialspoint7.myapplication;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.View;

public class MainActivity extends Activity {
   String msg = "Android : ";  

   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      Log.d(msg, "The onCreate() event");
   }

   public void startService(View view) {
      startService(new Intent(getBaseContext(), MyService.class));
   } 

   // Method to stop the service
   public void stopService(View view) {
      stopService(new Intent(getBaseContext(), MyService.class));
   }
}

Following is the content of MyService.java. This file can have implementation of one or more methods associated with Service based on requirements. For now we are going to implement only two methods onStartCommand() and onDestroy() −

Berikut adalah isi dari MyService.java. File ini dapat memiliki implementasi satu atau lebih metode yang terkait dengan Layanan berdasarkan persyaratan. Untuk saat ini kita hanya akan mengimplementasikan dua metode onStartCommand() dan onDestroy()

package com.example.tutorialspoint7.myapplication;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.widget.Toast;

/**
   * Created by TutorialsPoint7 on 8/23/2016.
*/

public class MyService extends Service {
   @Nullable
   @Override
   public IBinder onBind(Intent intent) {
      return null;
   }
	
   @Override
   public int onStartCommand(Intent intent, int flags, int startId) {
      // Let it continue running until it is stopped.
      Toast.makeText(this, "Service Started", Toast.LENGTH_LONG).show();
      return START_STICKY;
   }

   @Override
   public void onDestroy() {
      super.onDestroy();
      Toast.makeText(this, "Service Destroyed", Toast.LENGTH_LONG).show();
   }
}

Following will the modified content of AndroidManifest.xml file. Here we have added <service.../> tag to include our service − Berikut ini adalah konten yang dimodifikasi dari file AndroidManifest.xml. Di sini kami telah menambahkan tag <service.../> untuk menyertakan layanan kami

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.tutorialspoint7.myapplication">

   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">

      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
		
      <service android:name=".MyService" />
   </application>

</manifest>

Following will be the content of res/layout/activity_main.xml file to include two buttons −

Berikut ini adalah isi dari file res/layout/activity_main.xml untuk menyertakan dua tombol

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
   android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
   android:paddingRight="@dimen/activity_horizontal_margin"
   android:paddingTop="@dimen/activity_vertical_margin"
   android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">
   
   <TextView
      android:id="@+id/textView1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Example of services"
      android:layout_alignParentTop="true"
      android:layout_centerHorizontal="true"
      android:textSize="30dp" />
      
   <TextView
      android:id="@+id/textView2"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Tutorials point "
      android:textColor="#ff87ff09"
      android:textSize="30dp"
      android:layout_above="@+id/imageButton"
      android:layout_centerHorizontal="true"
      android:layout_marginBottom="40dp" /> 

   <ImageButton
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/imageButton"
      android:src="@drawable/abc"
      android:layout_centerVertical="true"
      android:layout_centerHorizontal="true" />

   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/button2"
      android:text="Start Services"
      android:onClick="startService"
      android:layout_below="@+id/imageButton"
      android:layout_centerHorizontal="true" />

   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Stop Services"
      android:id="@+id/button"
      android:onClick="stopService"
      android:layout_below="@+id/button2"
      android:layout_alignLeft="@+id/button2"
      android:layout_alignStart="@+id/button2"
      android:layout_alignRight="@+id/button2"
      android:layout_alignEnd="@+id/button2" />

</RelativeLayout>

Let's try to run our modified Hello World! application we just modified. I assume you had created your AVD while doing environment setup. To run the app from Android studio, open one of your project's activity files and click Run Android StudioRun Icon icon from the tool bar. Android Studio installs the app on your AVD and starts it and if everything is fine with your set-up and application, it will display following Emulator window −

Mari kita coba menjalankan Hello World yang telah dimodifikasi! aplikasi yang baru saja kami modifikasi. Saya berasumsi Anda telah membuat AVD Anda saat melakukan pengaturan lingkungan. Untuk menjalankan aplikasi dari Android studio, buka salah satu file aktivitas proyek Anda dan klik ikon Run Android StudioRun Icon dari bilah alat. Android Studio menginstal aplikasi pada AVD Anda dan memulainya dan jika semuanya baik-baik saja dengan pengaturan dan aplikasi Anda, itu akan menampilkan jendela Emulator berikut

Android Service Demo

Now to start your service, let's click on Start Service button, this will start the service and as per our programming in onStartCommand() method, a message Service Started will appear on the bottom of the the simulator as follows −

Sekarang untuk memulai layanan Anda, mari klik tombol Mulai Layanan, ini akan memulai layanan dan sesuai pemrograman kami dalam metode onStartCommand(), pesan Layanan Dimulai akan muncul di bagian bawah simulator sebagai berikut