initialized Application theme

lib/utils/helpers/life_cycle_event_handler.dart

@@ -0,0 +1,35 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+
+class LifecycleEventHandler extends WidgetsBindingObserver {
+  final AsyncCallback resumeCallBack;
+  final AsyncCallback suspendingCallBack;
+  final AsyncCallback onPauseCallBack;
+  final AsyncCallback inactiveCallBack;
+
+  LifecycleEventHandler(
+      {required this.resumeCallBack,
+      required this.suspendingCallBack,
+      required this.onPauseCallBack,
+      required this.inactiveCallBack});
+
+  @override
+  Future<void> didChangeAppLifecycleState(AppLifecycleState state) async {
+    switch (state) {
+      case AppLifecycleState.resumed:
+        await resumeCallBack();
+        break;
+      case AppLifecycleState.inactive:
+        await inactiveCallBack();
+        break;
+      case AppLifecycleState.paused:
+        await onPauseCallBack();
+        break;
+      case AppLifecycleState.detached:
+        await suspendingCallBack();
+        break;
+      case AppLifecycleState.hidden:
+      // TODO: Handle this case.
+    }
+  }
+}