Flutter - Call dart function from kotlin

Question

I'm building an app with flutter that gives you a notification with action buttons every 5 minutes. I use the android_alarm_manager and local_notifications package to implement that. Everything works fine and the alarm manager also works when I terminate the app but there is one problem. When I receive a notification and then clean the memory or wait too long the actions buttons don't work anymore.

I figured out that that's not a problem from Android because the listener is actually called (I tested it with a sysout), but because I cleaned the memory and so all apps were terminated, the MethodChannel (is set when initializing the local_notifiactions plugin) with that you can access the dart classes of flutter project is null. Consequently, the app can't access the notification action button clicked callback that I defined in my dart code.

So how can I initialize flutter from kotlin so that I can access the dart code of my project (without actually starting the app)?

Here is the code from the local_notifications library that calls the action button callback function in dart

private static boolean invokeCallback(String callbackName, String payload) {
    // getSharedChannel = null, because the app were terminated
    MethodChannel channel = LocalNotificationsService.getSharedChannel();

    if (channel != null) {
        /* I need the MethodChannel to call this function (invokeMethod)
           which calls my action button callback function in dart */
        channel.invokeMethod(callbackName, payload); 
        return true;
    } else {
        customLog("MethodChannel was null");
        return false;
    }
}

The getSharedChannel function just returns the variable, that was been set in the registerWith function, but that variable was reset because the memory has been cleared (but I want that my app also works when that happens)

public static MethodChannel getSharedChannel() {
    return sSharedChannel;
}

.

public static void registerWith(Registrar registrar) {
    final MethodChannel channel = new MethodChannel(registrar.messenger(), LocalNotificationsPlugin.CHANNEL_NAME);
    LocalNotificationsPlugin plugin = new LocalNotificationsPlugin(registrar);
    channel.setMethodCallHandler(plugin);
    registrar.addNewIntentListener(plugin);

    //The MethodChannel is set here, which can then be accessed with getSharedChannel
    LocalNotificationsService.setSharedChannel(channel);
}

@MohammadMirshahbazi Do you mean the code from the local_notifications library? — LukSN
Where is this code: LocalNotificationsService.getSharedChannel... Share this, too! — Akif
@Akif Okay sorry, I'm new to asking questions on Stack Overflow. I updated the questions with some more code. — LukSN

IL_Agent IL_Agent · Accepted Answer · 2021-08-25T20:55:35

The Flutter engine is bounded to Activity, that's why you can't use the channel when the activity destroyed. I guess you should send an intent by tap on your notification which starts an activity and invoke the channel there.

Flutter - Call dart function from kotlin

1 Answers