How to Create a Medicine Tracker Android App with Firebase?

class MedicineAlarmReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        // Create the notification channel (required for Android 8.0 and higher)
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            // unique id for the channel
            val channelId = "medicine_reminders"
          
            // name of the channel
            val channelName = "Medicine Reminders"
          
            // importance level of the channel
            val importance = NotificationManager.IMPORTANCE_HIGH 
          
            // creating channel
            val channel =
                NotificationChannel(channelId, channelName, importance) 
                
            // enabling lights for the channel
            channel.enableLights(true) 
            
            // setting light color for the channel
            channel.lightColor = Color.RED 
          
            // enabling vibration for the channel
            channel.enableVibration(true) 
            val notificationManager = context.getSystemService(NotificationManager::class.java)
            notificationManager?.createNotificationChannel(
                channel
            ) // registering the channel with the system
        }

        // Create the notification
        
        // unique id for the notification
        val notificationId = 1 
      
        // title of the notification
        val title = "Medicine Reminder" 
      
        // text of the notification
        val text = "It's time to take your medicine." 
        val intent =
            Intent(
                context,
                MainActivity::class.java
            ) // intent to launch when the notification is clicked
        val pendingIntent =
            PendingIntent.getActivity(
                context,
                0,
                intent,
                0
            ) // creating a pending intent to wrap the intent
            
        // creating the builder object
        val builder =
            NotificationCompat.Builder(context, "medicine_reminders") 
                .setSmallIcon(
                    R.drawable.ic_baseline_mediation_24
                ) // setting the small icon for the notification
                .setContentTitle(title) // setting the title for the notification
                .setContentText(text) // setting the text for the notification
                .setContentIntent(pendingIntent) // attaching the pending intent to the notification
                .setAutoCancel(
                    true
                ) // setting the notification to be automatically cancelled when clicked
                .setPriority(
                    NotificationCompat.PRIORITY_HIGH
                ) // setting the priority level of the notification

        // Display the notification
        
        // getting the notification manager
        val notificationManager =
            NotificationManagerCompat.from(context) 
            
        // displaying the notification
        notificationManager.notify(notificationId, builder.build()) 
    }
}

data class User (
    val medicineName : String ,
    val time : String
        )

class UserAdapter(private val list: ArrayList<User>) :
    RecyclerView.Adapter<UserAdapter.ViewHolder>() {

    // ViewHolder to hold reference to each item of the recycler view
    class ViewHolder(val binding: MedicineLayoutBinding) : RecyclerView.ViewHolder(binding.root) {}

    // inflating the layout and creating the ViewHolder when needed
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder(
            MedicineLayoutBinding.inflate(
                LayoutInflater.from(parent.context),
                parent,
                false
            )
        )
    }

    // binding data to the view in the viewholder
    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.binding.name.text = list[position].medicineName
        holder.binding.time.text = list[position].time
    }

    // returning the size of the data set
    override fun getItemCount(): Int {
        return list.size
    }
}

class MedicineAddActivity : AppCompatActivity(), TimePickerDialog.OnTimeSetListener {
    // reference to the database 
    private lateinit var database : DatabaseReference
    // reference to the layout binding object
    private lateinit var binding: ActivityMedicineAddBinding
    // variables to store the current time
    var hours = 0
    var minutes = 0
    // variables to store the selected time
    var myHours : Int = 0
    var myMinutes : Int= 0
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // inflating the layout and binding it to the binding object
        binding = ActivityMedicineAddBinding.inflate(layoutInflater)
        setContentView(binding.root)
        // setting a click listener on the select time button 
        binding.selectTime.setOnClickListener{
            val cal = Calendar.getInstance()
            // getting the current time 
            hours = cal.get(Calendar.HOUR)
            minutes = cal.get(Calendar.MINUTE)
            // creating a new time picker dialog 
            val timePickerDialog = TimePickerDialog(this,this,hours,minutes,true)
            timePickerDialog.show()
        }
    }
    // method called when the user sets the time on the time picker dialog
    override fun onTimeSet(view: TimePicker?, hourOfDay: Int, minute: Int) {
        myHours = hourOfDay
        myMinutes = minute
        // updating the text view that displays the selected time
        binding.etMedicineTime.text = "$myHours:$myMinutes"
        // setting a click listener on the save button
        binding.save.setOnClickListener{
            saveData()
        }
    }
}

private fun saveData() {
    // Reference to the "Users" node in the Firebase Database
    database = FirebaseDatabase.getInstance().getReference("Users")
    // Retrieve the value of the text from the "etMedicineName" TextView
    val medicineName = binding.etMedicineName.text.toString().trim()
    // Create a string with the selected time in the format "hours:minutes"
    val time = "$myHours:$myMinutes"
    // check if the medicineName is not empty
    if (medicineName.isNotEmpty()){
        // create a new User object with the 
        // entered medicine name and selected time
        val user = User(medicineName,time)
        // save the user object to the Firebase Database
        // under the "medicineName" key
        database.child(medicineName).setValue(user).addOnSuccessListener {
            // Clearing the EditText after saving the data
            binding.etMedicineName.text.clear()
            binding.etMedicineTime.text = "Select Time"
            Toast.makeText(this, "Success: Data saved to Firebase", Toast.LENGTH_SHORT).show()
        }.addOnFailureListener{
            Toast.makeText(this, "Error: Failed to save data to Firebase", Toast.LENGTH_SHORT).show()
        }
    }
    // call the setAlarm method to
    // set the alarm based on the selected time
    setAlarm()
}

 private fun setAlarm() {
        val alarmManager = getSystemService(Context.ALARM_SERVICE) as AlarmManager
        val intent = Intent(this, MedicineAlarmReceiver::class.java)
        val pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0)

        // Set the alarm to trigger at the specified time
        val calendar = Calendar.getInstance()
        calendar.timeInMillis = System.currentTimeMillis()
        calendar.set(Calendar.HOUR_OF_DAY, myHours)
        calendar.set(Calendar.MINUTE, myMinutes)

        alarmManager.setRepeating(
            AlarmManager.RTC_WAKEUP,
            calendar.timeInMillis,
            AlarmManager.INTERVAL_DAY,
            pendingIntent
        )
    }

package com.example.medicinetracker

import android.content.Intent
import android.os.Bundle
import android.util.Log
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.medicinetracker.databinding.ActivityMainBinding
import com.google.firebase.database.DatabaseError
import com.google.firebase.database.DatabaseReference
import com.google.firebase.database.FirebaseDatabase

class MainActivity : AppCompatActivity() {

    private lateinit var binding: ActivityMainBinding
    private lateinit var database: DatabaseReference
    private lateinit var userAdapter: UserAdapter
    private val medicineList = mutableListOf<User>()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        // Initialize Firebase Database
        database = FirebaseDatabase.getInstance().reference.child("Users")

        // Set up RecyclerView
        userAdapter = UserAdapter(medicineList)
        binding.recyclerView.layoutManager = LinearLayoutManager(this)
        binding.recyclerView.adapter = userAdapter

        // Load medicines from Firebase
        loadMedicines()

        // Set up "Add Medicine" button
        binding.btnAddMedicine.setOnClickListener {
            val intent = Intent(this, MedicineAddActivity::class.java)
            startActivity(intent)
        }
    }

    private fun loadMedicines() {
        database.addValueEventListener(object : com.google.firebase.database.ValueEventListener {
            override fun onDataChange(snapshot: com.google.firebase.database.DataSnapshot) {
                medicineList.clear()
                for (medicineSnapshot in snapshot.children) {
                    val medicine = medicineSnapshot.getValue(User::class.java)
                    medicine?.let { medicineList.add(it) }
                }
                userAdapter.notifyDataSetChanged()
            }

            override fun onCancelled(error: DatabaseError) {
                // Log the error
                Log.e("MainActivity", "Error loading medicines: ${error.message}")

                // Display a user-friendly message
                Toast.makeText(this@MainActivity, "Failed to load medicines. Please try again later.", Toast.LENGTH_LONG).show()
            }
        })
    }
}