adding more named and explicit imports (#1909)

animations/lib/src/misc/carousel.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:ui';
+import 'dart:ui' as ui;
 import 'package:flutter/material.dart';
 
 class CarouselDemo extends StatelessWidget {
@@ -80,8 +80,8 @@ class _CarouselState extends State<Carousel> {
       controller: _controller,
       scrollBehavior: ScrollConfiguration.of(context).copyWith(
         dragDevices: {
-          PointerDeviceKind.touch,
-          PointerDeviceKind.mouse,
+          ui.PointerDeviceKind.touch,
+          ui.PointerDeviceKind.mouse,
         },
       ),
       itemBuilder: (context, index) => AnimatedBuilder(