Notifications & Channels

val channel = NotificationChannel(
    "reminders",                                  // id – never change after release
    "Reminders",                                  // name shown in Settings
    NotificationManager.IMPORTANCE_HIGH           // heads-up + sound
).apply { description = "Homework and exam reminders" }
getSystemService(NotificationManager::class.java).createNotificationChannel(channel)

package com.codingeasily.studentdiary

import android.app.Application
import com.codingeasily.studentdiary.data.SettingsStore
import com.codingeasily.studentdiary.reminder.NotificationHelper

/**
 * Runs once when the app process starts (declared in AndroidManifest.xml).
 * We apply the saved light/dark theme and create the notification channel here.
 */
class StudentDiaryApp : Application() {
    override fun onCreate() {
        super.onCreate()
        SettingsStore(this).applyTheme()
        NotificationHelper.createChannel(this)
    }
}

val notification = NotificationCompat.Builder(this, "reminders")
    .setSmallIcon(R.drawable.ic_notification)     // white, transparent background
    .setContentTitle("⏰ Maths homework")
    .setContentText("Due tomorrow at 9:00 AM")
    .setPriority(NotificationCompat.PRIORITY_HIGH)
    .setAutoCancel(true)                          // remove after tap
    .build()

NotificationManagerCompat.from(this).notify(101, notification)   // 101 = id (same id replaces)

package com.codingeasily.studentdiary.reminder

import android.Manifest
import android.annotation.SuppressLint
import android.app.NotificationChannel
import android.app.NotificationManager
import android.app.PendingIntent
import android.content.Context
import android.content.Intent
import android.content.pm.PackageManager
import android.os.Build
import androidx.core.app.NotificationCompat
import androidx.core.app.NotificationManagerCompat
import androidx.core.content.ContextCompat
import com.codingeasily.studentdiary.MainActivity
import com.codingeasily.studentdiary.R

object NotificationHelper {

    const val CHANNEL_ID = "reminders"

    /** Android 8+ needs a channel before any notification can be shown. */
    fun createChannel(context: Context) {
        val channel = NotificationChannel(
            CHANNEL_ID,
            context.getString(R.string.channel_reminders),
            NotificationManager.IMPORTANCE_HIGH
        ).apply { description = context.getString(R.string.channel_reminders_desc) }
        context.getSystemService(NotificationManager::class.java).createNotificationChannel(channel)
    }

    fun canNotify(context: Context): Boolean =
        Build.VERSION.SDK_INT < Build.VERSION_CODES.TIRAMISU ||
            ContextCompat.checkSelfPermission(context, Manifest.permission.POST_NOTIFICATIONS) ==
            PackageManager.PERMISSION_GRANTED

    @SuppressLint("MissingPermission")          // we check canNotify() on the first line
    fun show(context: Context, noteId: Long, title: String, text: String) {
        if (!canNotify(context)) return

        // Tapping the notification opens the app
        val intent = Intent(context, MainActivity::class.java).apply {
            flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TOP
        }
        val pending = PendingIntent.getActivity(
            context, noteId.toInt(), intent,
            PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
        )

        val notification = NotificationCompat.Builder(context, CHANNEL_ID)
            .setSmallIcon(R.drawable.ic_notification)
            .setContentTitle(title)
            .setContentText(text)
            .setStyle(NotificationCompat.BigTextStyle().bigText(text))
            .setPriority(NotificationCompat.PRIORITY_HIGH)
            .setContentIntent(pending)
            .setAutoCancel(true)
            .build()

        try {
            NotificationManagerCompat.from(context).notify(noteId.toInt(), notification)
        } catch (e: SecurityException) {
            // permission was revoked while the app was running – ignore
        }
    }
}

// "Mark done" button handled by a BroadcastReceiver
val doneIntent = Intent(this, MarkDoneReceiver::class.java).putExtra("noteId", note.id)
val donePending = PendingIntent.getBroadcast(this, note.id.toInt(), doneIntent,
    PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE)

val builder = NotificationCompat.Builder(this, "reminders")
    .setSmallIcon(R.drawable.ic_notification)
    .setContentTitle("Maths homework")
    .addAction(R.drawable.ic_check, "Mark done", donePending)

// progress (e.g. uploading notes)
builder.setContentText("Uploading…").setProgress(100, 40, false)   // 40%
NotificationManagerCompat.from(this).notify(7, builder.build())