Invoke a method in flutter after restarting the device - flutter

Question

I build a to-do list app that should show notifications to remind about tasks. In order to be able to schedule the notifications to the exact minute of the deadline, I pass the notifications data from flutter to kotlin, and showing the notification from a Broadcast receiver.
Here I am sending the notifications data to kotlin:
await platform.invokeMethod('setNextNotification', {
'tasksNames': tasksNames,
'notificationsTimeInMillis': notificationsTimeInMillis
});
This is how I get the data inside FlutterActivity:
private const val CHANNEL = "flutter.native/helper"
class MainActivity : FlutterActivity() {
companion object {
const val TASKS_NAMES_EXTRA = "tasksNames"
const val NOTIFICATIONS_TIME_IN_MILLIS_EXTRA = "notificationsTimeInMillis"
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
GeneratedPluginRegistrant.registerWith(this)
// Init the AlarmManager.
val alarmManager = getSystemService(Context.ALARM_SERVICE) as AlarmManager
// We got here from the setNotifications() method in flutter...
MethodChannel(flutterView, CHANNEL).setMethodCallHandler { call, result ->
if (call.method == "setNextNotification") {
// Get the time till next notification
val notificationsTimeInMillis: ArrayList<Long> = call.argument(NOTIFICATIONS_TIME_IN_MILLIS_EXTRA)
?: ArrayList()
// Create a pending intent for the notifications
val pIntent: PendingIntent? = createPendingIntent(call.argument(TASKS_NAMES_EXTRA), call.argument(TIME_LEFT_TEXTS_EXTRA), notificationsTimeInMillis, this)
// Cancel all alarms
while (alarmManager.nextAlarmClock != null)
alarmManager.cancel(alarmManager.nextAlarmClock.showIntent)
// Set the alarm
setAlarm(notificationsTimeInMillis[0], pIntent, alarmManager)
}
}
}
private fun setAlarm(notificationTime: Long, pIntent: PendingIntent?, alarmManager: AlarmManager) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { // The API is 23 or higher...
alarmManager.setAlarmClock(AlarmManager.AlarmClockInfo(notificationTime, pIntent), pIntent)
} else { // The API is 19 - 22...
// We want the alarm to go of on the exact time it scheduled for so we use the setExact method.
alarmManager.setExact(AlarmManager.RTC_WAKEUP, notificationTime, pIntent)
}
}
private fun createPendingIntent(tasksNames: ArrayList<String>?, timeTillNotificationsInMillis: ArrayList<Long>?,
context: Context): android.app.PendingIntent? {
return try {
val intent: android.content.Intent = android.content.Intent(context, AlarmManagerHelperWakeful::class.java)
intent.action = "notification"
intent.putStringArrayListExtra(TASKS_NAMES_EXTRA, tasksNames)
intent.putStringArrayListExtra(NOTIFICATIONS_TIME_IN_MILLIS_EXTRA, timeTillNotificationsInMillisAsString)
android.app.PendingIntent.getBroadcast(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT)
} catch (e: java.lang.Exception) {
null
}
}
}
And this is how I show the notification on the BroadcastReceiver, and after that sets the next notification:
Class AlarmManagerHelperWakeful : BroadcastReceiver() {
override fun onReceive(context: Context?, intent: Intent?) {
if (intent != null && intent.action == "notification" && context != null) {
val tasksLabels: ArrayList<String> = intent.getStringArrayListExtra(MainActivity.TASKS_NAMES_EXTRA)
?: ArrayList()
val notificationsTimeInMillisAsString: ArrayList<String> = intent.getStringArrayListExtra(MainActivity.NOTIFICATIONS_TIME_IN_MILLIS_EXTRA)
?: ArrayList()
if (tasksLabels.size > 0) {
// Create a notification manager.
val notificationManager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
var builder = NotificationCompat.Builder(context) // The initialization is for api 25 or lower so it is deprecated.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) { // This is API 26 or higher...
// Create a channel for API 26 or higher;
val channelId = "channel_01" // The id of the channel.
if (notificationManager.getNotificationChannel(channelId) == null) {
val channel = NotificationChannel(channelId,
context.getString(R.string.notification_channel_name),
NotificationManager.IMPORTANCE_DEFAULT)
notificationManager.createNotificationChannel(channel)
}
// Update the builder to a no deprecated one.
builder = NotificationCompat.Builder(context, channelId)
}
// Set the notification details.
builder.setSmallIcon(android.R.drawable.ic_notification_overlay)
builder.setContentTitle(tasksLabels[0])
builder.setContentText(someText)
builder.priority = NotificationCompat.PRIORITY_DEFAULT
notificationId = someUniqueId
// Show the notification.
notificationManager.notify(notificationId.toInt(), builder.build())
// Remove this notification from the notifications lists.
tasksLabels.removeAt(0)
notificationsTimeInMillisAsString.removeAt(0)
// There are more notifications...
if (tasksLabels.size > 0) {
// Init the AlarmManager.
val alarmManager = context.getSystemService(Context.ALARM_SERVICE) as AlarmManager
// Cancel all alarms
while (alarmManager.nextAlarmClock != null)
alarmManager.cancel(alarmManager.nextAlarmClock.showIntent)
// Create a pending intent for the notifications
val pIntent: PendingIntent? = createPendingIntent(tasksLabels, cnotificationsTimeInMillisAsString, context)
// Set the alarm
setAlarm(notificationsTimeInMillisAsString[0].toLong(), pIntent, alarmManager)
}
}
} else {
if (intent == null) {
Log.d("Debug", "Checking: intent == null")
} else if ( intent.action != "notification") {
Log.d("Debug", "Checking: intent.action != notification")
val tasksLabels: ArrayList<String> = intent.getStringArrayListExtra(MainActivity.TASKS_NAMES_EXTRA)
?: ArrayList()
Log.d("Debug", "Checking: tasksNames.size inside else if" + tasksLabels.size)
}
}
}
}
Everything works perfectly fine unless I restart my device. Then the Broadcast receiver gets an intent without any data. For the BoradcastReceiver to get intent with notifications data, I need to invoke the method from the flutter code (the method that sends notifications data to the kotlin code), which means that for now, the user has to enter the app for that. Otherwise, user will not see notifications until entering my app and reinvoking the flutter code.
How can I overcome that issue?

Answer 1

You should use Push Notification instead of sending local notification to your broadcast receiver. There're lot of cases that make your app cannot send local notification. ex: user closed app (lot of users alway close app after using), OS closed app or clean memory, Dart method is crashing.
Firebase FCM is pretty simple, it's much more simple than you solution that's using broadcast receiver. Also totally free.
https://pub.dev/packages/firebase_messaging
Pushwoosh is good too, it has schedule notification
https://pub.dev/packages/pushwoosh
Using push notification also has other pros that you app will also work on iOS, doesn't need to keep your app running on background which is very bad idea if your app doesn't have any special features that need to run background (music player, geo location, VOIP)
In case you don't want to use Push Notification. Take a look at this lib:
https://pub.dev/packages/flutter_local_notifications

Answer 2

Right now you are sending data from dart to the native plugin. You might try it the other way around. This example shows how you can get the native android reboot event. Next, you can use this example to fetch the required data. After fetching the data you can set the notification.
You could also try to store the information of the last notification in SharedPreferences, fetch that on boot, and set the notification.