new dart 2.3.0 features to clean up collections

Author: prakhar1989

flutter-app/lib/labelscreen.dart

@@ -347,19 +347,6 @@ class _ListLabelsScreenState extends State<ListLabelsScreen> {
                 .map((document) => document["total_images"] as int)
                 .any((imageCount) => imageCount < 10);
 
-            final List<Widget> messages = [
-              new OperationProgress(dataset: widget.dataset)
-            ];
-
-            // If there are less than 10 images in the dataset, show a warning
-            if (invalidLabels) {
-              messages.add(new DismissibleMessageWidget(
-                msg:
-                    "At least 10 images per label are required to start training",
-                color: Colors.red[400],
-              ));
-            }
-
             final labelListView = new ListView(
                 children: snapshot.data.documents
                     .map((document) => new Container(
@@ -375,6 +362,17 @@ class _ListLabelsScreenState extends State<ListLabelsScreen> {
                         )))
                     .toList());
 
+            final List<Widget> messages = [
+              new OperationProgress(dataset: widget.dataset),
+              if (invalidLabels)
+                // If there are less than 10 images in the dataset, show a warning
+                new DismissibleMessageWidget(
+                  msg:
+                      "At least 10 images per label are required to start training",
+                  color: Colors.red[400],
+                ),
+            ];
+
             if (isOwner || isCollaborator) {
               return Column(
                   children: messages..add(new Expanded(child: labelListView)));

flutter-app/lib/operations_page.dart

@@ -68,6 +68,11 @@ class OperationsList extends StatelessWidget {
     );
   }
 
+  ListTile header(String text) => ListTile(
+      key: Key(text),
+      title: Text(text.toUpperCase(),
+          style: TextStyle(fontSize: 16, color: Colors.black54)));
+
   @override
   Widget build(BuildContext context) {
     return new StreamBuilder(
@@ -97,24 +102,14 @@ class OperationsList extends StatelessWidget {
                   .where((document) => document["done"])
                   .map(_toListTile);
 
-              final List<Widget> listTiles = [];
-              if (pendingOps.isNotEmpty) {
-                listTiles.add(ListTile(
-                  key: Key("in-progress"),
-                  title: Text("IN PROGRESS",
-                      style: TextStyle(fontSize: 16, color: Colors.black54)),
-                ));
-                listTiles.addAll(pendingOps);
-              }
-              if (completedOps.isNotEmpty) {
-                listTiles.add(ListTile(
-                  key: Key("completed"),
-                  title: Text("COMPLETED",
-                      style: TextStyle(fontSize: 16, color: Colors.black54)),
-                ));
-                listTiles.addAll(completedOps);
-              }
-              return ListView(children: listTiles);
+              return ListView(
+                children: [
+                  if (pendingOps.isNotEmpty) header("in progress"),
+                  if (pendingOps.isNotEmpty) ...pendingOps,
+                  if (completedOps.isNotEmpty) header("completed"),
+                  if (completedOps.isNotEmpty) ...completedOps,
+                ],
+              );
           }
         });
   }

flutter-app/pubspec.yaml

@@ -24,7 +24,7 @@ description: Crowdsource data for ML models
 version: 1.0.4
 
 environment:
-  sdk: ">=2.0.0-dev.68.0 <3.0.0"
+  sdk: ">=2.2.2 <3.0.0"
 
 dependencies:
   flutter: