Fix Spacer Widget

@@ -7,6 +7,7 @@
 - Fix PdfColors.fromHex()
 - Update Barcode library to 1.9.0
 - Fix exif orientation crash
+- Fix Spacer Widget
 
 ## 1.7.1
 

@@ -582,22 +582,15 @@ class Expanded extends Flexible {
 
 /// Spacer creates an adjustable, empty spacer that can be used to tune the
 /// spacing between widgets in a [Flex] container, like [Row] or [Column].
-class Spacer extends StatelessWidget {
-  Spacer({this.flex = 1})
+class Spacer extends Flexible {
+  Spacer({int flex = 1})
       : assert(flex != null),
         assert(flex > 0),
-        super();
-
-  /// The flex factor to use in determining how much space to take up.
-  final int flex;
-
-  @override
-  Widget build(Context context) {
-    return Expanded(
+        super(
           flex: flex,
+          fit: FlexFit.tight,
           child: SizedBox.shrink(),
         );
-  }
 }
 
 typedef IndexedWidgetBuilder = Widget Function(Context context, int index);

@@ -75,6 +75,24 @@ void main() {
     );
   });
 
+  test('Flex Widgets Spacer', () {
+    pdf.addPage(
+      Page(
+        build: (Context context) => Column(
+          children: <Widget>[
+            Text('Begin'),
+            Spacer(), // Defaults to a flex of one.
+            Text('Middle'),
+            // Gives twice the space between Middle and End than Begin and Middle.
+            Spacer(flex: 2),
+            // Expanded(flex: 2, child: SizedBox.shrink()),
+            Text('End'),
+          ],
+        ),
+      ),
+    );
+  });
+
   tearDownAll(() {
     final File file = File('widgets-flex.pdf');
     file.writeAsBytesSync(pdf.save());