fix date

Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/cupertino/cupertino_picker_demo.cs

           builder: (BuildContext context1) =>
           {
             return new _BottomPicker(
-              child: new CupertinoDatePicker(
+              child: new  CupertinoDatePicker(
-                onDateTimeChanged: (newDateTime) => { setState(() => date = newDateTime); }
+                onDateTimeChanged: (DateTime newDateTime) =>{
+                  setState(() => date = newDateTime);
+                }
               )
             );
           }
         children:new List<Widget>{
           new Text("Date and Time"),
           new Text(
-            dateTime.ToString("MMMM dd, yyyy h:mm tt"),
+            dateTime.ToString("MMMM dd, yyyy") + " " + dateTime.ToString("HH:mm tt"),
             style: new TextStyle(color: CupertinoDynamicColor.resolve(CupertinoColors.inactiveGray, context))
           ),
         }
           children: new List<Widget>{
             new Padding(padding: EdgeInsets.only(top: 32.0f)),
             _buildColorPicker(context),
-            //_buildCountdownTimerPicker(context),
-            //_buildDatePicker(context),
-            //_buildTimePicker(context),
-            //_buildDateAndTimePicker(context),
+            _buildCountdownTimerPicker(context),
+            _buildDatePicker(context),
+            _buildTimePicker(context),
+            _buildDateAndTimePicker(context),
           }
         )
       )

com.unity.uiwidgets/Runtime/cupertino/date_picker.cs

                             context,
                             new Text(
                                 localizations.datePickerYear(year),
-                                style: CupertinoDatePickerUtils._themeTextStyle(context, isValid: isValidYear))
+                                style: CupertinoDatePickerUtils._themeTextStyle(_context, isValid: isValidYear))
                         );
 
                     }
 
             List<Widget> pickers = new List<Widget>();
             for (int i = 0; i < columnWidths.Count; i++) {
-                float offAxisFraction = (i - 1) * 0.3f * textDirectionFactor;
+                int index = i;
+                float offAxisFraction = (index - 1) * 0.3f * textDirectionFactor;
+
+                Widget transitionBuilder(BuildContext _context, Widget child) {
+                    var columnWidth = columnWidths.Count == 0 ? 0 : columnWidths[index];
+                    var result = new Container(
+                        alignment: index == (columnWidths.Count - 1)
+                            ? alignCenterLeft
+                            : alignCenterRight,
+                        padding: index == 0 ? null : padding,
+                        child: new Container(
+                            alignment: index == 0 ? alignCenterLeft : alignCenterRight,
+                            width: columnWidth + CupertinoDatePickerUtils._kDatePickerPadSize,
+                            child: child
+                        )
+                    );
+                    return result;
+                }
+
+                TransitionBuilder builder = transitionBuilder;
+
+                Widget childWidget =  pickerBuilders[index](
+                    offAxisFraction: offAxisFraction,
+                    itemPositioningBuilder :  builder
+                ); 
-                    id: i,
-                    child: pickerBuilders[i](
-                        offAxisFraction,
-                        (BuildContext _context, Widget child) => {
-                            return new Container(
-                                alignment: i == columnWidths.Count - 1
-                                    ? alignCenterLeft
-                                    : alignCenterRight,
-                                padding: i == 0 ? null : padding,
-                                child: new Container(
-                                    alignment: i == 0 ? alignCenterLeft : alignCenterRight,
-                                    width: columnWidths[i] + CupertinoDatePickerUtils._kDatePickerPadSize,
-                                    child: child
-                                )
-                            );
-                        }
+                    id: index,
+                    child: childWidget
-                ));
+                );
             }
 
             return new MediaQuery(

com.unity.uiwidgets/Runtime/ui2/Matrix4.cs

         static float TOLERANCE = 0.000001f;
 
         public float[] storage {
-            get => _m4storage;
+            get { return _m4storage; }
         }
 
         public static void solve2(Matrix4 A, Vector2 x, Vector2 b) {