What is the proper way to create and use a BroadcastReceiver for an alarm manager inside an Activity?

I did have a look at the following answers but it's not clear to me whether I need to register the broadcast receiver and how to do so with the AlarmManager if it is. Also, it is not clear to me whether I should create the BroadcastReceiver inside the OnCreate() function or as class variable.

Broadcast Receiver in kotlin

Kotlin AlarmManager and BroadcastReceiver not working

Background:

I am trying to make an app that:

1. Plays a song at a specific time

2. Updates the time when the song should next be played

I was able to get 1) to work by creating a separate file for the BroadcastReceiver file as is commonly done, but then I am unable to access the AlarmManager because it is only available in the AppCompatActivity class. I also tried to use an intent to move back to the main activity and set the new alarm there, but that also did work because BroadcastReceiver does not have a context.

I am now trying to have the BroadcastReceiver inside the MainActivity but it does not get triggered:

private lateinit var picker: MaterialTimePicker
private lateinit var alarmManager: AlarmManager
private lateinit var calendar: Calendar

val broadCastReceiver = object : BroadcastReceiver() {
    override fun onReceive(context: Context?, intent: Intent?) {
        var mp = MediaPlayer.create(context, R.raw.song_title)

        mp.setVolume(1.0f, 1.0f)
        mp.start()
    }
}

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    var calendar = Calendar.getInstance()

    val intent = Intent(this, MainActivity::class.java)
    val pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0)
    alarmManager = getSystemService(ALARM_SERVICE) as AlarmManager

    val newDate = Calendar.getInstance()
    newDate.add(Calendar.MINUTE, 1)

    calendar[java.util.Calendar.HOUR_OF_DAY] = newDate.get(Calendar.HOUR_OF_DAY)
    calendar[java.util.Calendar.MINUTE] = newDate.get(Calendar.MINUTE)
    calendar[java.util.Calendar.SECOND] = 0
    calendar[java.util.Calendar.MILLISECOND] = 0

    alarmManager.setAndAllowWhileIdle(
        AlarmManager.RTC_WAKEUP,
        calendar.timeInMillis,
        pendingIntent
    )


}

}

CodePudding user response：

AlarmManager is not just only available in the AppCompatActivity class but from anywhere where you have access to Context as shown below:

class MyReceiver : BroadcastReceiver() {
override fun onReceive(context: Context?, intent: Intent?) {
    val alarmManager = context?.getSystemService(ALARM_SERVICE) as AlarmManager
  }
}

CodePudding user response：

After tweaking this answer I got it to work:

class MainActivity : ComponentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val receiver = object : BroadcastReceiver() {
            override fun onReceive(context: Context, intent: Intent) {
                var TAG = "check"
                Log.i(TAG,"==============")
                Log.i(TAG,"inside receiver")
                Log.i(TAG,"==============")
            }
        }

        this.registerReceiver(receiver, IntentFilter("TEST"))

        val intent = Intent()
        intent.action = "TEST"

        val alarmManager = this.getSystemService(ALARM_SERVICE) as? AlarmManager
        val pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0)

        val calendar = Calendar.getInstance()

        calendar.add(Calendar.SECOND, 10)

        alarmManager?.setAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, calendar.timeInMillis, pendingIntent)
        
    }
}

I can confirm that registering the receiver is indeed required.