App.javaAndroidManifest.xmlactivity_main.xmlExampleService.javaMainActivity.java
package com.codinginflow.foregroundserviceexample;

import android.app.Application;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.os.Build;


public class App extends Application {
    public static final String CHANNEL_ID = "exampleServiceChannel";

    @Override
    public void onCreate() {
        super.onCreate();

        createNotificationChannel();
    }

    private void createNotificationChannel() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel serviceChannel = new NotificationChannel(
                    CHANNEL_ID,
                    "Example Service Channel",
                    NotificationManager.IMPORTANCE_DEFAULT
            );

            NotificationManager manager = getSystemService(NotificationManager.class);
            manager.createNotificationChannel(serviceChannel);
        }
    }
}

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

    <application
        android:name=".App"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        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=".ExampleService" />
    </application>

</manifest>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:gravity="center"
    android:orientation="vertical"
    android:padding="16dp"
    tools:context="com.codinginflow.foregroundserviceexample.MainActivity">

    <EditText
        android:id="@+id/edit_text_input"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Input" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="startService"
        android:text="Start Service" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="stopService"
        android:text="Stop Service" />

</LinearLayout>

package com.codinginflow.foregroundserviceexample;

import android.app.Notification;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.support.v4.app.NotificationCompat;

import static com.codinginflow.foregroundserviceexample.App.CHANNEL_ID;


public class ExampleService extends Service {

    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        String input = intent.getStringExtra("inputExtra");

        Intent notificationIntent = new Intent(this, MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this,
                0, notificationIntent, 0);

        Notification notification = new NotificationCompat.Builder(this, CHANNEL_ID)
                .setContentTitle("Example Service")
                .setContentText(input)
                .setSmallIcon(R.drawable.ic_android)
                .setContentIntent(pendingIntent)
                .build();

        startForeground(1, notification);

        //do heavy work on a background thread
        //stopSelf();

        return START_NOT_STICKY;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
}

package com.codinginflow.foregroundserviceexample;

import android.content.Intent;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity {
    private EditText editTextInput;

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

        editTextInput = findViewById(R.id.edit_text_input);
    }

    public void startService(View v) {
        String input = editTextInput.getText().toString();

        Intent serviceIntent = new Intent(this, ExampleService.class);
        serviceIntent.putExtra("inputExtra", input);

        ContextCompat.startForegroundService(this, serviceIntent);
    }

    public void stopService(View v) {
        Intent serviceIntent = new Intent(this, ExampleService.class);
        stopService(serviceIntent);
    }
}