MyWorker.java

package com.manoj.workmanager;

import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.content.Context;
import android.os.Build;
import androidx.annotation.NonNull;
import androidx.core.app.NotificationCompat;
import androidx.work.Worker;
import androidx.work.WorkerParameters;

/**
 * This is Worker class where we define our background Task.
 * For this class we need dependency that is 'androidx.work:work-runtime:2.2.0'
 * or higher( Which is alpha version and not recommended )
 *
 * */

public class MyWorker extends Worker {

    public MyWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
        super(context, workerParams);
    }

    @NonNull
    @Override
    public Result doWork() {
        //here we define background task
        displayNotification("WorkManager","Background task has been completed");
        return Result.success();
    }


    //Sample notification for testing purpose
    private void displayNotification(String task, String desp){
        NotificationManager manager = (NotificationManager) getApplicationContext()
                .getSystemService(Context.NOTIFICATION_SERVICE);

        if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.O){
            NotificationChannel channel = new NotificationChannel("Test","Test",NotificationManager.IMPORTANCE_DEFAULT);
            manager.createNotificationChannel(channel);
        }
        NotificationCompat.Builder builder = new NotificationCompat.Builder(getApplicationContext(), "Test")
                .setContentTitle(task)
                .setContentText(desp)
                .setSmallIcon(R.mipmap.ic_launcher);

        manager.notify(1, builder.build());
    }
}