Merge pull request #4 from Sasikumar3595/master

FLUT-4313-Sample updated with null safety.

Author: Nijamudeen-Mohamed

README.md

@@ -3,20 +3,11 @@
 In flutter date range picker, you can get the current month start and end dates using the `onViewChanged` callback.
 
 ## Step 1:
-In initState(), initialize the controller for the date range picker and set the default values for start and end dates of the current month.
+Inside the state, initialize the controller for the date range picker and set the default values for start and end date of the current month.
 
 ```xml
-DateRangePickerController _controller;
-String _startDate, _endDate;
- 
-@override
-void initState() {
-  // TODO: implement initState
-  _controller = DateRangePickerController();
-  _startDate = '';
-  _endDate = '';
-  super.initState();
-}
+final DateRangePickerController _controller = DateRangePickerController();
+String _startDate = '', _endDate = '';
 ```
 
 ## Step 2:
@@ -48,12 +39,12 @@ Using the `onViewChanged` callback of the date picker get the start and dates of
 void viewChanged(DateRangePickerViewChangedArgs args) {
 
     _startDate = DateFormat('dd, MMMM yyyy')
-        .format(args.visibleDateRange.startDate)
+        .format(args.visibleDateRange.startDate!)
         .toString();
     _endDate=DateFormat('dd, MMMM yyyy')
-        .format(args.visibleDateRange.endDate)
+        .format(args.visibleDateRange.endDate!)
         .toString();
-    SchedulerBinding.instance.addPostFrameCallback((duration) {
+    SchedulerBinding.instance!.addPostFrameCallback((duration) {
       setState(() {});
     });
 }

lib/main.dart

@@ -21,77 +21,64 @@ class PickerCurrentMonth extends StatefulWidget {
   _PickerCurrentMonthState createState() => _PickerCurrentMonthState();
 }
 
-List<String> views = <String>['Month', 'Year', 'Decade', 'Century'];
-
 class _PickerCurrentMonthState extends State<PickerCurrentMonth> {
-  DateRangePickerController _controller;
-  String _startDate, _endDate;
-
-  @override
-  void initState() {
-    // TODO: implement initState
-    _controller = DateRangePickerController();
-    _startDate = '';
-    _endDate = '';
-    super.initState();
-  }
+  final DateRangePickerController _controller = DateRangePickerController();
+  final List<String> views = <String>['Month', 'Year', 'Decade', 'Century'];
+  String _startDate = '', _endDate = '';
 
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-        appBar: AppBar(
-          leading: PopupMenuButton<String>(
-            icon: Icon(Icons.calendar_today),
-            itemBuilder: (BuildContext context) => views.map((String choice) {
-              return PopupMenuItem<String>(
-                value: choice,
-                child: Text(choice),
-              );
-            }).toList(),
-            onSelected: (String value) {
-              if (value == 'Month') {
-                _controller.view = DateRangePickerView.month;
-              } else if (value == 'Year') {
-                _controller.view = DateRangePickerView.year;
-              } else if (value == 'Decade') {
-                _controller.view = DateRangePickerView.decade;
-              } else if (value == 'Century') {
-                _controller.view = DateRangePickerView.century;
-              }
-            },
-          ),
-        ),
-        body: Column(
-          children: <Widget>[
-            Container( height:50,
-                child: Text('StartDate:''$_startDate')),
-            Container(height:50
-                ,child: Text('EndDate:''$_endDate')),
-            Card(
-              margin: const EdgeInsets.fromLTRB(40, 100, 50, 40),
-              child: SfDateRangePicker(
-                controller: _controller,
-                view: DateRangePickerView.month,
-                onViewChanged: viewChanged,
-              ),
-            )
-          ],
+      appBar: AppBar(
+        leading: PopupMenuButton<String>(
+          icon: Icon(Icons.calendar_today),
+          itemBuilder: (BuildContext context) => views.map((String choice) {
+            return PopupMenuItem<String>(
+              value: choice,
+              child: Text(choice),
+            );
+          }).toList(),
+          onSelected: (String value) {
+            if (value == 'Month') {
+              _controller.view = DateRangePickerView.month;
+            } else if (value == 'Year') {
+              _controller.view = DateRangePickerView.year;
+            } else if (value == 'Decade') {
+              _controller.view = DateRangePickerView.decade;
+            } else if (value == 'Century') {
+              _controller.view = DateRangePickerView.century;
+            }
+          },
         ),
+      ),
+      body: Column(
+        children: <Widget>[
+          Container(height: 50, child: Text('StartDate:' '$_startDate')),
+          Container(height: 50, child: Text('EndDate:' '$_endDate')),
+          Card(
+            margin: const EdgeInsets.fromLTRB(40, 100, 50, 40),
+            child: SfDateRangePicker(
+              controller: _controller,
+              view: DateRangePickerView.month,
+              onViewChanged: viewChanged,
+            ),
+          )
+        ],
+      ),
 
-        // This trailing comma makes auto-formatting nicer for build methods.
-        );
+      // This trailing comma makes auto-formatting nicer for build methods.
+    );
   }
 
   void viewChanged(DateRangePickerViewChangedArgs args) {
-
-      _startDate = DateFormat('dd, MMMM yyyy')
-          .format(args.visibleDateRange.startDate)
-          .toString();
-      _endDate=DateFormat('dd, MMMM yyyy')
-          .format(args.visibleDateRange.endDate)
-          .toString();
-      SchedulerBinding.instance.addPostFrameCallback((duration) {
-        setState(() {});
-      });
+    _startDate = DateFormat('dd, MMMM yyyy')
+        .format(args.visibleDateRange.startDate!)
+        .toString();
+    _endDate = DateFormat('dd, MMMM yyyy')
+        .format(args.visibleDateRange.endDate!)
+        .toString();
+    SchedulerBinding.instance!.addPostFrameCallback((duration) {
+      setState(() {});
+    });
   }
 }