Added credentials form.

lib/ui/credentials_form.dart

@@ -0,0 +1,80 @@
+import 'package:flutter/material.dart';
+
+
+class CredentialsForm extends StatefulWidget {
+  CredentialsForm({Key key}) : super(key: key);
+
+  @override
+  _CredentialsState createState() => _CredentialsState();
+}
+
+class _CredentialsState extends State<CredentialsForm> {
+  String username;
+  String password;
+  bool _hidden = true;
+  final _credFormKey = GlobalKey<FormState>();
+  InputDecoration _textFieldDecoration(String label, IconData icon) {
+    return InputDecoration(
+      labelText: label,
+      icon: Icon(icon),
+      hintText: 'Please, insert your zucchetti account $label',
+    );
+  }
+
+  String validateUsername(String username) {
+    if (username.isEmpty) {
+      return 'Username must not be empty';
+    }
+    return null;
+  }
+
+  String validatePassword(String password) {
+    if (password.isEmpty) {
+      return 'Password must not be empty';
+    }
+    return null;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Form(
+        key: _credFormKey,
+        child: Column(children: <Widget>[
+          TextFormField(
+              autofocus: true,
+              autocorrect: false,
+              decoration:
+                  this._textFieldDecoration("username", Icons.alternate_email),
+              validator: this.validateUsername),
+          TextFormField(
+              autocorrect: false,
+              decoration: this._textFieldDecoration("password", Icons.lock),
+              validator: this.validatePassword,
+              obscureText: this._hidden),
+          Row(
+          mainAxisAlignment: MainAxisAlignment.spaceBetween,
+          children: <Widget>[
+            RaisedButton(
+              onPressed: () {
+                if (_credFormKey.currentState.validate()) {
+                  Scaffold.of(context)
+                      .showSnackBar(SnackBar(content: Text('Processing Data')));
+                }
+              },
+              child: Text('Validate'),
+            ),
+            Row(children: <Widget>[
+              Text('Reveal password'),
+              Checkbox(
+                  value: !this._hidden,
+                  onChanged: (bool value) {
+                    setState(() {
+                      _hidden = !value;
+                    });
+                    return;
+                  })
+            ])
+          ]),
+        ]));
+  }
+}