Added missing comments for the snackbar code, extracted snackbar related code from the screens constructors to a method

lib/src/mixins/upload_status_mixin.dart

@@ -22,11 +22,17 @@ mixin UploadStatusMixin {
   /// An observable of the status of files being uploaded.
   Observable<UploadStatus> get uploadStatus => uploadStatusSer.status;
 
+  /// Disposes instance variables that are part of the mixin.
   Future<void> disposeUploadStatusMixin() async {
     await snackBarStatusSubject.drain();
     snackBarStatusSubject.close();
   }
 
+  /// Initializes the [snacBarStatusSubject].
+  ///
+  /// The raw status coming from the [UploadStatusService] is transformed and
+  /// turned into a stream that emits [true] when the snackbar should be visible
+  /// and false otherwise. This is piped to [the snackBarStatusSubject].
   void initializeSnackBarStatus() {
     uploadStatusService.status
         .transform(StreamTransformer<UploadStatus, bool>.fromHandlers(

lib/src/screens/event_screen.dart

@@ -41,6 +41,7 @@ class _EventScreenState extends State<EventScreen>
   /// Needed for showing snackbars.
   BuildContext _scaffoldContext;
 
+  /// A stream subscription to the snackbar status.
   StreamSubscription _snackBarStatusSubscription;
 
   initState() {
@@ -49,17 +50,7 @@ class _EventScreenState extends State<EventScreen>
     bloc.fetchTasks();
     bloc.fetchImagesPaths();
     _tabController = TabController(vsync: this, length: 2);
-    _snackBarStatusSubscription = bloc.snackBarStatus.listen((bool visible) {
-      if (visible) {
-        showUploadStatusSnackBar(
-          _scaffoldContext,
-          bloc.uploadStatus,
-          bloc.updateSnackBarStatus,
-        );
-      } else {
-        Scaffold.of(_scaffoldContext).hideCurrentSnackBar();
-      }
-    });
+    initializeSnackBarListener();
   }
 
   Widget build(BuildContext context) {
@@ -204,6 +195,20 @@ class _EventScreenState extends State<EventScreen>
     );
   }
 
+  void initializeSnackBarListener() {
+    _snackBarStatusSubscription = bloc.snackBarStatus.listen((bool visible) {
+      if (visible) {
+        showUploadStatusSnackBar(
+          _scaffoldContext,
+          bloc.uploadStatus,
+          bloc.updateSnackBarStatus,
+        );
+      } else {
+        Scaffold.of(_scaffoldContext).hideCurrentSnackBar();
+      }
+    });
+  }
+
   void dispose() {
     _snackBarStatusSubscription.cancel();
     bloc.dispose();

lib/src/screens/home_screen.dart

@@ -28,23 +28,14 @@ class _HomeScreenState extends State<HomeScreen> {
   /// Needed for showing snackbars.
   BuildContext _scaffoldContext;
 
+  /// A stream subscription to the snackbar status.
   StreamSubscription _snackBarStatusSubscription;
 
   @override
   initState() {
     super.initState();
     bloc.fetchTasks();
-    _snackBarStatusSubscription = bloc.snackBarStatus.listen((bool visible) {
-      if (visible) {
-        showUploadStatusSnackBar(
-          _scaffoldContext,
-          bloc.uploadStatus,
-          bloc.updateSnackBarStatus,
-        );
-      } else {
-        Scaffold.of(_scaffoldContext).hideCurrentSnackBar();
-      }
-    });
+    initializeSnackBarListener();
   }
 
   Widget build(BuildContext context) {
@@ -138,6 +129,20 @@ class _HomeScreenState extends State<HomeScreen> {
     );
   }
 
+  void initializeSnackBarListener() {
+    _snackBarStatusSubscription = bloc.snackBarStatus.listen((bool visible) {
+      if (visible) {
+        showUploadStatusSnackBar(
+          _scaffoldContext,
+          bloc.uploadStatus,
+          bloc.updateSnackBarStatus,
+        );
+      } else {
+        Scaffold.of(_scaffoldContext).hideCurrentSnackBar();
+      }
+    });
+  }
+
   @override
   void dispose() {
     _snackBarStatusSubscription.cancel();

lib/src/utils.dart

@@ -1,5 +1,4 @@
 import 'dart:async';
-import 'dart:collection';
 
 import 'package:flutter/material.dart';
 import 'package:rxdart/rxdart.dart';