Keyboard navigation for the Material Date Picker grid (#59586)

packages/flutter/lib/src/material/pickers/date_picker_dialog.dart

@@ -6,7 +6,7 @@
 
 import 'dart:math' as math;
 
-import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
 import '../button_bar.dart';
@@ -357,6 +357,11 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
     return null;
   }
 
+  static final Map<LogicalKeySet, Intent> _formShortcutMap = <LogicalKeySet, Intent>{
+    // Pressing enter on the field will move focus to the next field or control.
+    LogicalKeySet(LogicalKeyboardKey.enter): const NextFocusIntent(),
+  };
+
   @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
@@ -419,24 +424,27 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
           child: Container(
             padding: const EdgeInsets.symmetric(horizontal: 24),
             height: orientation == Orientation.portrait ? _inputFormPortraitHeight : _inputFormLandscapeHeight,
-            child: Column(
-              children: <Widget>[
-                const Spacer(),
-                InputDatePickerFormField(
-                  initialDate: _selectedDate,
-                  firstDate: widget.firstDate,
-                  lastDate: widget.lastDate,
-                  onDateSubmitted: _handleDateChanged,
-                  onDateSaved: _handleDateChanged,
-                  selectableDayPredicate: widget.selectableDayPredicate,
-                  errorFormatText: widget.errorFormatText,
-                  errorInvalidText: widget.errorInvalidText,
-                  fieldHintText: widget.fieldHintText,
-                  fieldLabelText: widget.fieldLabelText,
-                  autofocus: true,
-                ),
-                const Spacer(),
-              ],
+            child: Shortcuts(
+              shortcuts: _formShortcutMap,
+              child: Column(
+                children: <Widget>[
+                  const Spacer(),
+                  InputDatePickerFormField(
+                    initialDate: _selectedDate,
+                    firstDate: widget.firstDate,
+                    lastDate: widget.lastDate,
+                    onDateSubmitted: _handleDateChanged,
+                    onDateSaved: _handleDateChanged,
+                    selectableDayPredicate: widget.selectableDayPredicate,
+                    errorFormatText: widget.errorFormatText,
+                    errorInvalidText: widget.errorInvalidText,
+                    fieldHintText: widget.fieldHintText,
+                    fieldLabelText: widget.fieldLabelText,
+                    autofocus: true,
+                  ),
+                  const Spacer(),
+                ],
+              ),
             ),
           ),
         );

packages/flutter/lib/src/material/pickers/date_utils.dart

@@ -26,12 +26,20 @@ DateTimeRange datesOnly(DateTimeRange range) {
 }
 
 /// Returns true if the two [DateTime] objects have the same day, month, and
-/// year.
+/// year, or are both null.
 bool isSameDay(DateTime dateA, DateTime dateB) {
   return
-    dateA.year == dateB.year &&
-    dateA.month == dateB.month &&
-    dateA.day == dateB.day;
+    dateA?.year == dateB?.year &&
+    dateA?.month == dateB?.month &&
+    dateA?.day == dateB?.day;
+}
+
+/// Returns true if the two [DateTime] objects have the same month, and
+/// year, or are both null.
+bool isSameMonth(DateTime dateA, DateTime dateB) {
+  return
+    dateA?.year == dateB?.year &&
+    dateA?.month == dateB?.month;
 }
 
 /// Determines the number of months between two [DateTime] objects.