Changed duration (#19015)

* Changed duration

* Fixed column width for ios build error messages

* fixed a couple things

* fixed a couple things

* accidental changes

* added spaces

* added spaces

* Added test for default snackbar duration

* Fixed link:

* Final commit

* Final commit2

* Actual final commit

packages/flutter/lib/src/material/snack_bar.dart

@@ -11,7 +11,6 @@ import 'scaffold.dart';
 import 'theme.dart';
 import 'theme_data.dart';
 
-// https://material.google.com/components/snackbars-toasts.html#snackbars-toasts-specs
 const double _kSnackBarPadding = 24.0;
 const double _kSingleLineVerticalPadding = 14.0;
 const Color _kSnackBackground = const Color(0xFF323232);
@@ -23,7 +22,7 @@ const Color _kSnackBackground = const Color(0xFF323232);
 // TODO(ianh): Implement the Tablet version of snackbar if we're "on a tablet".
 
 const Duration _kSnackBarTransitionDuration = const Duration(milliseconds: 250);
-const Duration _kSnackBarDisplayDuration = const Duration(milliseconds: 1500);
+const Duration _kSnackBarDisplayDuration = const Duration(milliseconds: 4000);
 const Curve _snackBarHeightCurve = Curves.fastOutSlowIn;
 const Curve _snackBarFadeCurve = const Interval(0.72, 1.0, curve: Curves.fastOutSlowIn);
 
@@ -71,7 +70,7 @@ enum SnackBarClosedReason {
 /// See also:
 ///
 ///  * [SnackBar]
-///  * <https://material.google.com/components/snackbars-toasts.html>
+///  * <https://material.io/design/components/snackbars.html>
 class SnackBarAction extends StatefulWidget {
   /// Creates an action for a [SnackBar].
   ///
@@ -136,7 +135,7 @@ class _SnackBarActionState extends State<SnackBarAction> {
 ///    displayed snack bar, if any, and allows the next to be displayed.
 ///  * [SnackBarAction], which is used to specify an [action] button to show
 ///    on the snack bar.
-///  * <https://material.google.com/components/snackbars-toasts.html>
+///  * <https://material.io/design/components/snackbars.html>
 class SnackBar extends StatelessWidget {
   /// Creates a snack bar.
   ///
@@ -169,14 +168,14 @@ class SnackBar extends StatelessWidget {
 
   /// The amount of time the snack bar should be displayed.
   ///
-  /// Defaults to 1.5s.
+  /// Defaults to 4.0s.
   ///
   /// See also:
   ///
   ///  * [ScaffoldState.removeCurrentSnackBar], which abruptly hides the
   ///    currently displayed snack bar, if any, and allows the next to be
   ///    displayed.
-  ///  * <https://material.google.com/components/snackbars-toasts.html>
+  ///  * <https://material.io/design/components/snackbars.html>
   final Duration duration;
 
   /// The animation driving the entrance and exit of the snack bar.

packages/flutter/test/material/snack_bar_test.dart

@@ -482,4 +482,52 @@ void main() {
     expect(closedReason, equals(SnackBarClosedReason.timeout));
   });
 
+  testWidgets('SnackBar default display duration test', (WidgetTester tester) async {
+    const String helloSnackBar = 'Hello SnackBar';
+    const Key tapTarget = const Key('tap-target');
+    await tester.pumpWidget(new MaterialApp(
+        home: new Scaffold(
+            body: new Builder(
+                builder: (BuildContext context) {
+                  return new GestureDetector(
+                      onTap: () {
+                        Scaffold.of(context).showSnackBar(const SnackBar(
+                            content: const Text(helloSnackBar)
+                        ));
+                      },
+                      behavior: HitTestBehavior.opaque,
+                      child: new Container(
+                          height: 100.0,
+                          width: 100.0,
+                          key: tapTarget
+                      )
+                  );
+                }
+            )
+        )
+    ));
+    expect(find.text(helloSnackBar), findsNothing);
+    await tester.tap(find.byKey(tapTarget));
+    expect(find.text(helloSnackBar), findsNothing);
+    await tester.pump(); // schedule animation
+    expect(find.text(helloSnackBar), findsOneWidget);
+    await tester.pump(); // begin animation
+    expect(find.text(helloSnackBar), findsOneWidget);
+    await tester.pump(const Duration(milliseconds: 750)); // 0.75s // animation last frame; four second timer starts here
+    expect(find.text(helloSnackBar), findsOneWidget);
+    await tester.pump(const Duration(milliseconds: 750)); // 1.50s
+    expect(find.text(helloSnackBar), findsOneWidget);
+    await tester.pump(const Duration(milliseconds: 750)); // 2.25s
+    expect(find.text(helloSnackBar), findsOneWidget);
+    await tester.pump(const Duration(milliseconds: 750)); // 3.00s
+    expect(find.text(helloSnackBar), findsOneWidget);
+    await tester.pump(const Duration(milliseconds: 750)); // 3.75s
+    expect(find.text(helloSnackBar), findsOneWidget);
+    await tester.pump(const Duration(milliseconds: 1000)); // 4.75s // timer triggers to dismiss snackbar, reverse animation is scheduled
+    await tester.pump(); // begin animation
+    expect(find.text(helloSnackBar), findsOneWidget); // frame 0 of dismiss animation
+    await tester.pump(const Duration(milliseconds: 750)); // 5.50s // last frame of animation, snackbar removed from build
+    expect(find.text(helloSnackBar), findsNothing);
+  });
+
 }