Migrate to the New Material Buttons (#668)

form_app/lib/src/form_widgets.dart

@@ -190,7 +190,7 @@ class _FormDatePickerState extends State<_FormDatePicker> {
             ),
           ],
         ),
-        FlatButton(
+        TextButton(
           child: Text('Edit'),
           onPressed: () async {
             var newDate = await showDatePicker(

form_app/lib/src/sign_in_http.dart

@@ -73,7 +73,7 @@ class _SignInHttpDemoState extends State<SignInHttpDemo> {
                       formData.password = value;
                     },
                   ),
-                  FlatButton(
+                  TextButton(
                     child: Text('Sign in'),
                     onPressed: () async {
                       // Use a JSON encoded string to send
@@ -113,7 +113,7 @@ class _SignInHttpDemoState extends State<SignInHttpDemo> {
       builder: (context) => AlertDialog(
         title: Text(message),
         actions: [
-          FlatButton(
+          TextButton(
             child: Text('OK'),
             onPressed: () => Navigator.of(context).pop(),
           ),

form_app/lib/src/validation.dart

@@ -24,8 +24,8 @@ class _FormValidationDemoState extends State<FormValidationDemo> {
         actions: [
           Padding(
             padding: EdgeInsets.all(8),
-            child: FlatButton(
-              textColor: Colors.white,
+            child: TextButton(
+              style: TextButton.styleFrom(primary: Colors.white),
               child: Text('Submit'),
               onPressed: () {
                 // Validate the form by getting the FormState from the GlobalKey
@@ -41,7 +41,7 @@ class _FormValidationDemoState extends State<FormValidationDemo> {
                     title: Text('Your story'),
                     content: Text('The $adjective developer saw a $noun'),
                     actions: [
-                      FlatButton(
+                      TextButton(
                         child: Text('Done'),
                         onPressed: () {
                           Navigator.of(context).pop();