Allow the app to request for permission later

android/build.gradle

@@ -5,7 +5,7 @@ buildscript {
     ext.kotlin_version = '1.3.50'
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 
     dependencies {
@@ -17,7 +17,7 @@ buildscript {
 rootProject.allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 }
 

android/src/main/kotlin/com/emilecode/android_notification_listener2/AndroidNotificationListener2Plugin.kt

@@ -4,23 +4,39 @@ package com.emilecode.android_notification_listener2
 /**
  * Flutter-specific
  */
+import android.app.Activity
+import android.app.Service
 import io.flutter.plugin.common.EventChannel
 import io.flutter.plugin.common.EventChannel.StreamHandler
 import io.flutter.plugin.common.EventChannel.EventSink
-import io.flutter.plugin.common.PluginRegistry.Registrar
 
 /**
  * Android-specific
  */
 import android.content.*
+import android.os.Handler
 import android.provider.Settings
 import android.text.TextUtils
+import io.flutter.embedding.engine.plugins.FlutterPlugin
+import io.flutter.plugin.common.MethodChannel
+import io.flutter.embedding.engine.FlutterEngine
+
+import androidx.annotation.NonNull
+import io.flutter.embedding.engine.plugins.activity.ActivityAware
+import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding
+import io.flutter.embedding.engine.plugins.service.ServicePluginBinding
+import java.lang.Exception
+import java.lang.reflect.Method
+import io.flutter.embedding.engine.plugins.service.ServiceAware as ServiceAware
+
 
 /**
  * AndroidNotificationListener2Plugin
  */
-class AndroidNotificationListener2Plugin private constructor(private val context: Context) : StreamHandler {
+class AndroidNotificationListener2Plugin : StreamHandler, FlutterPlugin {
   private var eventSink: EventSink? = null
+  private var methodChannel: MethodChannel? = null
+  private var context: Context? = null
 
   /**
    * Called whenever the event channel is subscribed to in Flutter
@@ -31,7 +47,7 @@ class AndroidNotificationListener2Plugin private constructor(private val context
       Start the notification service once permission has been given.
      */
     val listenerIntent = Intent(context, NotificationListener::class.java)
-    context.startService(listenerIntent)
+    context!!.startService(listenerIntent)
   }
 
   /**
@@ -46,8 +62,8 @@ class AndroidNotificationListener2Plugin private constructor(private val context
    * If any match is found, return true. Otherwise if no matches were found, return false.
    */
   private fun permissionGiven(): Boolean {
-    val packageName = context.packageName
-    val flat = Settings.Secure.getString(context.contentResolver,
+    val packageName = context!!.packageName
+    val flat = Settings.Secure.getString(context!!.contentResolver,
             ENABLED_NOTIFICATION_LISTENERS)
     if (!TextUtils.isEmpty(flat)) {
       val names = flat.split(":").toTypedArray()
@@ -83,32 +99,64 @@ class AndroidNotificationListener2Plugin private constructor(private val context
     private const val ENABLED_NOTIFICATION_LISTENERS = "enabled_notification_listeners"
     private const val ACTION_NOTIFICATION_LISTENER_SETTINGS = "android.settings.ACTION_NOTIFICATION_LISTENER_SETTINGS"
     private const val EVENT_CHANNEL_NAME = "notifications.eventChannel"
-
-    /** Plugin registration.  */
-    @JvmStatic
-    fun registerWith(registrar: Registrar) {
-      val channel = EventChannel(registrar.messenger(), EVENT_CHANNEL_NAME)
-      val context: Context = registrar.activeContext()
-      val plugin = AndroidNotificationListener2Plugin(context)
-      channel.setStreamHandler(plugin)
-    }
+    private const val COMMAND_CHANEL = "notifications.commandChannel"
   }
 
   /**
    * Plugin constructor setting the context and registering the notification service.
    */
   init {
+
+  }
+
+  fun lateInit() {
     /* Check if permission is given, if not then go to the notification settings screen. */
     if (!permissionGiven()) {
-      context.startActivity(Intent(ACTION_NOTIFICATION_LISTENER_SETTINGS))
+      requestPermission()
     }
     val receiver = NotificationReceiver()
     val intentFilter = IntentFilter()
     intentFilter.addAction(NotificationListener.NOTIFICATION_INTENT)
-    context.registerReceiver(receiver, intentFilter)
+    context!!.registerReceiver(receiver, intentFilter)
 
     /* Start the notification service once permission has been given. */
     val listenerIntent = Intent(context, NotificationListener::class.java)
-    context.startService(listenerIntent)
+    context!!.startService(listenerIntent)
+  }
+
+  private fun requestPermission() {
+    val intent = Intent(ACTION_NOTIFICATION_LISTENER_SETTINGS)
+    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
+    context?.startActivity(intent)
+  }
+
+  override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+    this.context = binding.applicationContext
+    EventChannel(binding.binaryMessenger, EVENT_CHANNEL_NAME).setStreamHandler(this)
+    methodChannel = MethodChannel(binding.getBinaryMessenger(), COMMAND_CHANEL)
+    methodChannel!!.setMethodCallHandler { call, result ->
+      run {
+        when (call.method) {
+          "init" -> {
+            lateInit()
+            result.success(null)
+          }
+          "permissionGiven" -> result.success(permissionGiven())
+          "requestPermission" -> {
+            requestPermission()
+            result.success(null)
+          }
+          else -> { // Note the block
+            throw UnsupportedOperationException("Method ${call.method} is not supported")
+          }
+        }
+      }
+    }
+  }
+
+  override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+    methodChannel?.setMethodCallHandler(null)
+    methodChannel = null
+    this.context = null
   }
 }

example/lib/main.dart

@@ -11,19 +11,30 @@ class MyApp extends StatefulWidget {
   _MyAppState createState() => _MyAppState();
 }
 
-class _MyAppState extends State<MyApp> {
+class _MyAppState extends State<MyApp> with WidgetsBindingObserver {
   AndroidNotificationListener _notifications;
   StreamSubscription<NotificationEventV2> _subscription;
+  bool _permissionGiven = false;
+  bool _inited = false;
 
   @override
   void initState() {
     super.initState();
+    WidgetsBinding.instance.addObserver(this);
     initPlatformState();
   }
 
   // Platform messages are asynchronous, so we initialize in an async method.
   Future<void> initPlatformState() async {
     startListening();
+    updatePermissionState();
+  }
+
+  Future<void> updatePermissionState() async {
+    var permissionGiven = await _notifications.isPermissionGiven();
+    setState(() {
+      _permissionGiven = permissionGiven;
+    });
   }
 
   void onData(NotificationEventV2 event) {
@@ -35,7 +46,7 @@ class _MyAppState extends State<MyApp> {
   }
 
   void startListening() {
-    _notifications = new AndroidNotificationListener();
+    _notifications = AndroidNotificationListener.withoutInit();
     try {
       _subscription = _notifications.notificationStream.listen(onData);
     } on NotificationExceptionV2 catch (exception) {
@@ -54,7 +65,42 @@ class _MyAppState extends State<MyApp> {
         appBar: AppBar(
           title: const Text('Plugin example app'),
         ),
-      ),
+        body: Column(children: [
+          _permissionGiven
+              ? Text("Permission has granted")
+              : Text("Permission has not grant"),
+          _inited
+              ? Text("Plugin inited")
+              : Text("Plugin not inited"),
+          TextButton(
+            child: Text("Init"),
+            onPressed: () {
+              _notifications.init();
+              setState(() {
+                _inited = _notifications.isInited;
+              });
+            },
+          ),
+          TextButton(
+            child: Text("request permission"),
+            onPressed: () {
+              _notifications.requestPermission();
+            },
+          ),
+        ])),
     );
   }
+
+  @override
+  void didChangeAppLifecycleState(AppLifecycleState state) {
+    if (state == AppLifecycleState.resumed) {
+      updatePermissionState();
+    }
+  }
+
+  @override
+  void dispose() {
+    super.dispose();
+    WidgetsBinding.instance.removeObserver(this);
+  }
 }