Hướng dẫn sử dụng Service trong Android

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button_play"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="28dp"
        android:text="Play"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button_stop"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="37dp"
        android:text="Stop"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button_play" />
</androidx.constraintlayout.widget.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.o7planning.playsongservice">

    <application ...>

        <service
            android:name=".PlaySongService"
            android:enabled="true"
            android:exported="true"></service>

            ....

    </application>

</manifest>

package org.o7planning.playsongservice;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.media.MediaPlayer;

public class PlaySongService extends Service {

    private MediaPlayer mediaPlayer;

    public PlaySongService() {
    }

    // Return the communication channel to the service.
    @Override
    public IBinder onBind(Intent intent){
        // This service is unbounded
        // So this method is never called.
        return null;
    }


    @Override
    public void onCreate(){
        super.onCreate();
        // Create MediaPlayer object, to play your song.
        mediaPlayer = MediaPlayer.create(getApplicationContext(), R.raw.mysong);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId){
        // Play song.
        mediaPlayer.start();

        return START_STICKY;
    }

    // Destroy
    @Override
    public void onDestroy() {
        // Release the resources
        mediaPlayer.release();
        super.onDestroy();
    }
}

package org.o7planning.playsongservice;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.content.Intent;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

    private Button buttonPlay;
    private Button buttonStop;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        this.buttonPlay = (Button) this.findViewById(R.id.button_play);
        this.buttonStop = (Button) this.findViewById(R.id.button_stop);

        this.buttonPlay.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                playSong();
            }
        });

        this.buttonStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                stopSong();
            }
        });
    }

    // This method is called when users click on the Play button.
    public void playSong()  {
        // Create Intent object for PlaySongService.
        Intent myIntent = new Intent(MainActivity.this, PlaySongService.class);

        // Call startService with Intent parameter.
        this.startService(myIntent);
    }

    // This method is called when users click on the Stop button.
    public void stopSong( )  {
        
        // Create Intent object
        Intent myIntent = new Intent(MainActivity.this, PlaySongService.class);
        this.stopService(myIntent);
    }

}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="38dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="17dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Location:"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editText_location"
        android:layout_width="0dp"
        android:layout_height="47dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="23dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:ems="10"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <TextView
        android:id="@+id/textView_weather"
        android:layout_width="0dp"
        android:layout_height="45dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="59dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText_location" />

    <Button
        android:id="@+id/button_weather"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="35dp"
        android:text="Show Weather"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView_weather" />
</androidx.constraintlayout.widget.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.o7planning.weatherservice">

    <application ...>
        <service
            android:name=".WeatherService"
            android:enabled="true"
            android:exported="true"></service>

        ...

    </application>

</manifest>

package org.o7planning.weatherservice;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.Binder;
import android.util.Log;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;


public class WeatherService extends Service {

    private static String LOG_TAG = "WeatherService";

    // Store the weather data.
    private static final Map<String, String> weatherData = new HashMap<String,String>();

    private final IBinder binder = new LocalWeatherBinder();

    public class LocalWeatherBinder extends Binder {

        public WeatherService getService()  {
            return WeatherService.this;
        }
    }

    public WeatherService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        Log.i(LOG_TAG,"onBind");
        return this.binder;
    }

    @Override
    public void onRebind(Intent intent) {
        Log.i(LOG_TAG, "onRebind");
        super.onRebind(intent);
    }

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

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

    // Returns the weather information corresponding to the location of the current date.
    public String getWeatherToday(String location) {
        Date now= new Date();
        DateFormat df= new SimpleDateFormat("dd-MM-yyyy");

        String dayString = df.format(now);
        String keyLocAndDay = location + "$"+ dayString;

        String weather=  weatherData.get(keyLocAndDay);
        //
        if(weather != null)  {
            return weather;
        }

        //
        String[] weathers = new String[]{"Rainy", "Hot", "Cool", "Warm" ,"Snowy"};

        // Random value from 0 to 4
        int i= new Random().nextInt(5);

        weather =weathers[i];
        weatherData.put(keyLocAndDay, weather);
        //
        return weather;
    }

}

package org.o7planning.weatherservice;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.IBinder;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private boolean binded = false;
    private WeatherService weatherService;

    private TextView textViewWeather;
    private EditText editTextLocation;
    private Button buttonWeather;

    ServiceConnection weatherServiceConnection = new ServiceConnection() {

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            WeatherService.LocalWeatherBinder binder = (WeatherService.LocalWeatherBinder) service;
            weatherService = binder.getService();
            binded = true;
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            binded = false;
        }
    };

    // When the Activity creating its interface.
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        this.textViewWeather = (TextView) this.findViewById(R.id.textView_weather);
        this.editTextLocation = (EditText) this.findViewById(R.id.editText_location);
        this.buttonWeather = (Button) this.findViewById(R.id.button_weather);

        this.buttonWeather.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                 showWeather();
            }
        });
    }

    // When Activity starting.
    @Override
    protected void onStart() {
        super.onStart();

        // Create Intent object for WeatherService.
        Intent intent = new Intent(this, WeatherService.class);

        // Call bindService(..) method to bind service with UI.
        this.bindService(intent, weatherServiceConnection, Context.BIND_AUTO_CREATE);
    }

    // Activity stop
    @Override
    protected void onStop() {
        super.onStop();
        if (binded) {
            // Unbind Service
            this.unbindService(weatherServiceConnection);
            binded = false;
        }
    }

    // When user click on 'Show weather' button.
    public void showWeather()  {
        String location = this.editTextLocation.getText().toString();

        String weather= this.weatherService.getWeatherToday(location);

        this.textViewWeather.setText(weather);
    }

}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="0dp"
        android:layout_height="25dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="28dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView_percent"
        android:layout_width="0dp"
        android:layout_height="22dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="28dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:gravity="center"
        android:text="(Percent)"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/progressBar" />

    <Button
        android:id="@+id/button_start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="27dp"
        android:text="Start"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView_percent" />

    <Button
        android:id="@+id/button_stop"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="26dp"
        android:text="Stop"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button_start" />
</androidx.constraintlayout.widget.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.o7planning.simpleintentservice">

    <application ...>
        <service
            android:name=".SimpleIntentService"
            android:exported="false"></service>

        ...
    </application>

</manifest>

package org.o7planning.simpleintentservice;

import android.app.IntentService;
import android.content.Intent;
import android.os.SystemClock;

public class SimpleIntentService extends IntentService {

    public static volatile boolean shouldStop = false;

    public static final String ACTION_1 ="MY_ACTION_1";

    public static final String PARAM_PERCENT = "percent";

    public SimpleIntentService() {
        super("SimpleIntentService");
    }

    @Override
    protected void onHandleIntent(Intent intent) {

        // Create Intent object (to broadcast).
        Intent broadcastIntent = new Intent();

        // Set Action name for this Intent.
        // A Intent can perform many different actions.
        broadcastIntent.setAction(SimpleIntentService.ACTION_1);

        // Loop 100 times broadcast of Intent.
        for (int i = 0; i <= 100; i++) {

            // Set data
            // (Percent of work)
            broadcastIntent.putExtra(PARAM_PERCENT, i);

            // Send broadcast
            sendBroadcast(broadcastIntent);

            // Sleep 100 Milliseconds.
            SystemClock.sleep(100);

            if(shouldStop) {
                stopSelf();
                return;
            }
        }

    }
}

package org.o7planning.simpleintentservice;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.AsyncTask;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private Button buttonStart;
    private Button buttonStop;
    private TextView textViewPercent;

    private ProgressBar progressBar;

    private Intent serviceIntent;

    private ResponseReceiver receiver = new ResponseReceiver();


    // Broadcast component
    public class ResponseReceiver extends BroadcastReceiver {

        // On broadcast received
        @Override
        public void onReceive(Context context, Intent intent) {

            // Check action name.
            if(intent.getAction().equals(SimpleIntentService.ACTION_1)) {
                int value = intent.getIntExtra(SimpleIntentService.PARAM_PERCENT, 0);

                new ShowProgressBarTask().execute(value);
            }
        }
    }

    // Display value for the ProgressBar.
    class ShowProgressBarTask extends AsyncTask<Integer, Integer, Integer> {

        @Override
        protected Integer doInBackground(Integer... args) {

            return args[0];
        }

        @Override
        protected void onPostExecute(Integer result) {
            super.onPostExecute(result);

            progressBar.setProgress(result);

            textViewPercent.setText(result + " % Loaded");

            if (result == 100) {
                textViewPercent.setText("Completed");
                buttonStart.setEnabled(true);
            }

        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        this.textViewPercent = (TextView) this.findViewById(R.id.textView_percent);
        this.progressBar = (ProgressBar) this.findViewById(R.id.progressBar);
        this.buttonStart = (Button) this.findViewById(R.id.button_start);
        this.buttonStop = (Button)this.findViewById(R.id.button_stop);

        this.buttonStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                buttonStartClicked();
            }
        });

        this.buttonStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                buttonStopClicked();
            }
        });
    }


    // On Resume of MainActivity
    @Override
    protected void onResume() {
        super.onResume();

        // Register receiver with Activity.
        registerReceiver(receiver, new IntentFilter(
                SimpleIntentService.ACTION_1));
    }

    // On Stop of MainActivity
    @Override
    protected void onStop() {
        super.onStop();

        // Unregister receiver with Activity.
        unregisterReceiver(receiver);
    }

    // Method is called when the user clicks on the Start button.
    public void buttonStartClicked( )  {
        this.buttonStart.setEnabled(false);

        this.serviceIntent = new Intent(this, SimpleIntentService.class);

        startService(this.serviceIntent);
    }


    public void buttonStopClicked( )  {
        if(this.serviceIntent!= null)  {
            // stopService(this.serviceIntent) does not work with IntentService(s).

            // Mandatory stopping of an IntentService is not recommended.
            SimpleIntentService.shouldStop = true;
        }
    }

}