Added a Form widget to manage multiple Input widgets.

examples/material_gallery/lib/demo/text_field_demo.dart

@@ -11,14 +11,16 @@ class TextFieldDemo extends StatefulWidget {
   TextFieldDemoState createState() => new TextFieldDemoState();
 }
 
+class PersonData {
+  String name;
+  String phoneNumber;
+  String password;
+}
+
 class TextFieldDemoState extends State<TextFieldDemo> {
   final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
-  final List<InputValue> _inputs = <InputValue>[
-    InputValue.empty,
-    InputValue.empty,
-    InputValue.empty,
-    InputValue.empty,
-  ];
+
+  PersonData person = new PersonData();
 
   void showInSnackBar(String value) {
     _scaffoldKey.currentState.showSnackBar(new SnackBar(
@@ -26,36 +28,30 @@ class TextFieldDemoState extends State<TextFieldDemo> {
     ));
   }
 
-  void _handleInputChanged(InputValue value, int which) {
-    setState(() {
-      _inputs[which] = value;
-    });
-  }
-
-  void _handleInputSubmitted(InputValue value) {
-    showInSnackBar('${_inputs[0].text}\'s phone number is ${_inputs[1].text}');
+  void _handleSubmitted() {
+    showInSnackBar('${person.name}\'s phone number is ${person.phoneNumber}');
   }
 
-  String _validateName(InputValue value) {
-    if (value.text.isEmpty)
+  String _validateName(String value) {
+    if (value.isEmpty)
       return 'Name is required.';
     RegExp nameExp = new RegExp(r'^[A-za-z ]+$');
-    if (!nameExp.hasMatch(value.text))
+    if (!nameExp.hasMatch(value))
       return 'Please enter only alphabetical characters.';
     return null;
   }
 
-  String _validatePhoneNumber(InputValue value) {
+  String _validatePhoneNumber(String value) {
     RegExp phoneExp = new RegExp(r'^\d\d\d-\d\d\d\-\d\d\d\d$');
-    if (!phoneExp.hasMatch(value.text))
+    if (!phoneExp.hasMatch(value))
       return '###-###-#### - Please enter a valid phone number.';
     return null;
   }
 
-  String _validatePassword(InputValue value1, InputValue value2) {
-    if (value1.text.isEmpty)
+  String _validatePassword(String value) {
+    if (person.password == null || person.password.isEmpty)
       return 'Please choose a password.';
-    if (value1.text != value2.text)
+    if (person.password != value)
       return 'Passwords don\'t match';
     return null;
   }
@@ -67,24 +63,27 @@ class TextFieldDemoState extends State<TextFieldDemo> {
       appBar: new AppBar(
         title: new Text('Text Fields')
       ),
-      body: new Block(
+      body: new Form(
+        onSubmitted: _handleSubmitted,
+        child: new Block(
           padding: const EdgeInsets.all(8.0),
           children: <Widget>[
             new Input(
               hintText: 'What do people call you?',
               labelText: 'Name',
-            errorText: _validateName(_inputs[0]),
-            value: _inputs[0],
-            onChanged: (InputValue value) { _handleInputChanged(value, 0); },
-            onSubmitted: _handleInputSubmitted
+              formField: new FormField<String>(
+                // TODO(mpcomplete): replace with person#name=
+                setter:  (String val) { person.name = val; },
+                validator: _validateName
+              )
             ),
             new Input(
               hintText: 'Where can we reach you?',
               labelText: 'Phone Number',
-            errorText: _validatePhoneNumber(_inputs[1]),
-            value: _inputs[1],
-            onChanged: (InputValue value) { _handleInputChanged(value, 1); },
-            onSubmitted: _handleInputSubmitted
+              formField: new FormField<String>(
+                setter: (String val) { person.phoneNumber = val; },
+                validator: _validatePhoneNumber
+              )
             ),
             new Row(
               crossAxisAlignment: CrossAxisAlignment.start,
@@ -94,26 +93,26 @@ class TextFieldDemoState extends State<TextFieldDemo> {
                     hintText: 'How do you log in?',
                     labelText: 'New Password',
                     hideText: true,
-                  value: _inputs[2],
-                  onChanged: (InputValue value) { _handleInputChanged(value, 2); },
-                  onSubmitted: _handleInputSubmitted
+                    formField: new FormField<String>(
+                      setter: (String val) { person.password = val; }
+                    )
                   )
                 ),
                 new Flexible(
                   child: new Input(
                     hintText: 'How do you log in?',
                     labelText: 'Re-type Password',
-                  errorText: _validatePassword(_inputs[2], _inputs[3]),
                     hideText: true,
-                  value: _inputs[3],
-                  onChanged: (InputValue value) { _handleInputChanged(value, 3); },
-                  onSubmitted: _handleInputSubmitted
+                    formField: new FormField<String>(
+                      validator: _validatePassword
+                    )
                   )
                 )
               ]
             )
           ]
         )
+      )
     );
   }
 }

packages/flutter/lib/src/material/input.dart

@@ -17,7 +17,7 @@ export 'package:sky_services/editing/editing.mojom.dart' show KeyboardType;
 class Input extends StatefulWidget {
   Input({
     Key key,
-    this.value: InputValue.empty,
+    this.value,
     this.keyboardType: KeyboardType.text,
     this.icon,
     this.labelText,
@@ -27,6 +27,7 @@ class Input extends StatefulWidget {
     this.hideText: false,
     this.isDense: false,
     this.autofocus: false,
+    this.formField,
     this.onChanged,
     this.onSubmitted
   }) : super(key: key);
@@ -61,6 +62,9 @@ class Input extends StatefulWidget {
   /// Whether this input field should focus itself is nothing else is already focused.
   final bool autofocus;
 
+  /// Form-specific data, required if this Input is part of a Form.
+  final FormField<String> formField;
+
   /// Called when the text being edited changes.
   final ValueChanged<InputValue> onChanged;
 
@@ -79,12 +83,24 @@ class _InputState extends State<Input> {
 
   GlobalKey get focusKey => config.key is GlobalKey ? config.key : _rawInputLineKey;
 
+  // Optional state to retain if we are inside a Form widget.
+  _FormFieldData _formData;
+
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
     ThemeData themeData = Theme.of(context);
     BuildContext focusContext = focusKey.currentContext;
     bool focused = focusContext != null && Focus.at(focusContext, autofocus: config.autofocus);
+    if (_formData == null)
+      _formData = _FormFieldData.maybeCreate(context, this);
+    InputValue value = config.value ?? _formData?.value ?? InputValue.empty;
+    ValueChanged<InputValue> onChanged = config.onChanged ?? _formData?.onChanged;
+    ValueChanged<InputValue> onSubmitted = config.onSubmitted ?? _formData?.onSubmitted;
+    String errorText = config.errorText;
+
+    if (errorText == null && config.formField != null && config.formField.validator != null)
+      errorText = config.formField.validator(value.text);
 
     TextStyle textStyle = config.style ?? themeData.textTheme.subhead;
     Color activeColor = themeData.hintColor;
@@ -102,7 +118,7 @@ class _InputState extends State<Input> {
 
     List<Widget> stackChildren = <Widget>[];
 
-    bool hasInlineLabel = config.labelText != null && !focused && !config.value.text.isNotEmpty;
+    bool hasInlineLabel = config.labelText != null && !focused && !value.text.isNotEmpty;
 
     if (config.labelText != null) {
       TextStyle labelStyle = hasInlineLabel ?
@@ -125,7 +141,7 @@ class _InputState extends State<Input> {
       topPadding += topPaddingIncrement;
     }
 
-    if (config.hintText != null && config.value.text.isEmpty && !hasInlineLabel) {
+    if (config.hintText != null && value.text.isEmpty && !hasInlineLabel) {
       TextStyle hintStyle = themeData.textTheme.subhead.copyWith(color: themeData.hintColor);
       stackChildren.add(new Positioned(
         left: 0.0,
@@ -139,7 +155,7 @@ class _InputState extends State<Input> {
     Color borderColor = activeColor;
     double borderWidth = focused ? 2.0 : 1.0;
 
-    if (config.errorText != null) {
+    if (errorText != null) {
       borderColor = themeData.errorColor;
       borderWidth = 2.0;
       if (!config.isDense) {
@@ -163,24 +179,24 @@ class _InputState extends State<Input> {
       ),
       child: new RawInputLine(
         key: _rawInputLineKey,
-        value: config.value,
+        value: value,
         focusKey: focusKey,
         style: textStyle,
         hideText: config.hideText,
         cursorColor: themeData.selectionColor,
         selectionColor: themeData.selectionColor,
         keyboardType: config.keyboardType,
-        onChanged: config.onChanged,
-        onSubmitted: config.onSubmitted
+        onChanged: onChanged,
+        onSubmitted: onSubmitted
       )
     ));
 
-    if (config.errorText != null && !config.isDense) {
+    if (errorText != null && !config.isDense) {
       TextStyle errorStyle = themeData.textTheme.caption.copyWith(color: themeData.errorColor);
       stackChildren.add(new Positioned(
         left: 0.0,
         bottom: 0.0,
-        child: new Text(config.errorText, style: errorStyle)
+        child: new Text(errorText, style: errorStyle)
       ));
     }
 
@@ -216,3 +232,36 @@ class _InputState extends State<Input> {
     );
   }
 }
+
+class _FormFieldData {
+  _FormFieldData(this.inputState) {
+    assert(field != null);
+  }
+
+  InputValue value = new InputValue();
+  final _InputState inputState;
+  FormField<String> get field => inputState.config.formField;
+
+  static _FormFieldData maybeCreate(BuildContext context, _InputState inputState) {
+    // Only create a _FormFieldData if this Input is a descendent of a Form.
+    if (FormScope.of(context) != null)
+      return new _FormFieldData(inputState);
+    return null;
+  }
+
+  void onChanged(InputValue value) {
+    FormScope scope = FormScope.of(inputState.context);
+    assert(scope != null);
+    this.value = value;
+    if (field.setter != null)
+      field.setter(value.text);
+    scope.onFieldChanged();
+  }
+
+  void onSubmitted(InputValue value) {
+    FormScope scope = FormScope.of(inputState.context);
+    assert(scope != null);
+    scope.form.onSubmitted();
+    scope.onFieldChanged();
+  }
+}

packages/flutter/lib/src/widgets/form.dart

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'basic.dart';
+import 'framework.dart';
+
+/// A container for grouping together multiple form field widgets (e.g. Input).
+class Form extends StatefulWidget {
+  Form({
+    Key key,
+    this.child,
+    this.onSubmitted
+  }) : super(key: key) {
+    assert(child != null);
+  }
+
+  /// Called when the input is accepted anywhere on the form.
+  final VoidCallback onSubmitted;
+
+  /// Root of the widget hierarchy that contains this form.
+  final Widget child;
+
+  @override
+  _FormState createState() => new _FormState();
+}
+
+class _FormState extends State<Form> {
+  int generation = 0;
+
+  void onFieldChanged() {
+    setState(() {
+      ++generation;
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return new FormScope(
+      state: this,
+      generation: generation,
+      child: config.child
+    );
+  }
+}
+
+typedef String FormFieldValidator<T>(T value);
+typedef void FormFieldSetter<T>(T newValue);
+
+/// This contains identifying information for Input fields, required if the
+/// Input is part of a Form.
+class FormField<T> {
+  FormField({
+    this.setter,
+    this.validator
+  });
+
+  /// An optional method to call with the new value when the form field changes.
+  final FormFieldSetter<T> setter;
+
+  /// An optional method that validates an input. Returns an error string to
+  /// display if the input is invalid, or null otherwise.
+  final FormFieldValidator<T> validator;
+}
+
+/// The root of all Forms. Used by form field widgets (e.g. Input) to
+/// communicate changes back to the client.
+class FormScope extends InheritedWidget {
+  FormScope({
+    Key key,
+    Widget child,
+    _FormState state,
+    int generation
+  }) : _state = state,
+       _generation = generation,
+       super(key: key, child: child);
+
+  final _FormState _state;
+
+  /// Incremented every time a form field has changed. This lets us know when
+  /// to rebuild the form.
+  final int _generation;
+
+  /// The Form this widget belongs to.
+  Form get form => _state.config;
+
+  /// Finds the FormScope that encloses the widget being built from the given
+  /// context.
+  static FormScope of(BuildContext context) {
+    return context.inheritFromWidgetOfExactType(FormScope);
+  }
+
+  /// Use this to notify the Form that a form field has changed. This will
+  /// cause all form fields to rebuild, useful if form fields have
+  /// interdependencies.
+  void onFieldChanged() => _state.onFieldChanged();
+
+  @override
+  bool updateShouldNotify(FormScope old) => _generation != old._generation;
+}

packages/flutter/lib/widgets.dart

@@ -17,6 +17,7 @@ export 'src/widgets/dismissable.dart';
 export 'src/widgets/drag_target.dart';
 export 'src/widgets/editable.dart';
 export 'src/widgets/focus.dart';
+export 'src/widgets/form.dart';
 export 'src/widgets/framework.dart';
 export 'src/widgets/gesture_detector.dart';
 export 'src/widgets/gridpaper.dart';

packages/flutter/test/widget/form_test.dart

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter/material.dart';
+import 'package:sky_services/editing/editing.mojom.dart' as mojom;
+import 'package:test/test.dart';
+
+class MockKeyboard implements mojom.Keyboard {
+  mojom.KeyboardClient client;
+
+  @override
+  void setClient(mojom.KeyboardClientStub client, mojom.KeyboardConfiguration configuraiton) {
+    this.client = client.impl;
+  }
+
+  @override
+  void show() {}
+
+  @override
+  void hide() {}
+
+  @override
+  void setEditingState(mojom.EditingState state) {}
+}
+
+void main() {
+  WidgetFlutterBinding.ensureInitialized(); // for serviceMocker
+  MockKeyboard mockKeyboard = new MockKeyboard();
+  serviceMocker.registerMockService(mojom.Keyboard.serviceName, mockKeyboard);
+
+  void enterText(String testValue) {
+    // Simulate entry of text through the keyboard.
+    expect(mockKeyboard.client, isNotNull);
+    mockKeyboard.client.updateEditingState(new mojom.EditingState()
+      ..text = testValue
+      ..composingBase = 0
+      ..composingExtent = testValue.length);
+  }
+
+  test('Setter callback is called', () {
+    testWidgets((WidgetTester tester) {
+      GlobalKey inputKey = new GlobalKey();
+      String fieldValue;
+
+      Widget builder() {
+        return new Center(
+          child: new Material(
+            child: new Form(
+              child: new Input(
+                key: inputKey,
+                formField: new FormField<String>(
+                  setter: (String val) { fieldValue = val; }
+                )
+              )
+            )
+          )
+        );
+      }
+
+      tester.pumpWidget(builder());
+
+      void checkText(String testValue) {
+        enterText(testValue);
+
+        // Check that the FormField's setter was called.
+        expect(fieldValue, equals(testValue));
+        tester.pumpWidget(builder());
+      }
+
+      checkText('Test');
+      checkText('');
+    });
+  });
+
+  test('Validator sets the error text', () {
+    testWidgets((WidgetTester tester) {
+      GlobalKey inputKey = new GlobalKey();
+      String errorText(String input) => input + '/error';
+
+      Widget builder() {
+        return new Center(
+          child: new Material(
+            child: new Form(
+              child: new Input(
+                key: inputKey,
+                formField: new FormField<String>(
+                  validator: errorText
+                )
+              )
+            )
+          )
+        );
+      }
+
+      tester.pumpWidget(builder());
+
+      void checkErrorText(String testValue) {
+        enterText(testValue);
+        tester.pumpWidget(builder());
+
+        // Check for a new Text widget with our error text.
+        Element errorElement = tester.findText(errorText(testValue));
+        expect(errorElement, isNotNull);
+      }
+
+      checkErrorText('Test');
+      checkErrorText('');
+    });
+  });
+
+  test('Multiple Inputs communicate', () {
+    testWidgets((WidgetTester tester) {
+      GlobalKey inputKey = new GlobalKey();
+      GlobalKey focusKey = new GlobalKey();
+      // Input 1's text value.
+      String fieldValue;
+      // Input 2's validator depends on a input 1's value.
+      String errorText(String input) => fieldValue.toString() + '/error';
+
+      Widget builder() {
+        return new Center(
+          child: new Material(
+            child: new Form(
+              child: new Focus(
+                key: focusKey,
+                child: new Block(
+                  children: <Widget>[
+                    new Input(
+                      key: inputKey,
+                      formField: new FormField<String>(
+                        setter: (String val) { fieldValue = val; }
+                      )
+                    ),
+                    new Input(
+                      formField: new FormField<String>(
+                        validator: errorText
+                      )
+                    )
+                  ]
+                )
+              )
+            )
+          )
+        );
+      }
+
+      tester.pumpWidget(builder());
+      Focus.moveTo(inputKey);
+      tester.pump();
+
+      void checkErrorText(String testValue) {
+        enterText(testValue);
+        tester.pumpWidget(builder());
+
+        expect(fieldValue, equals(testValue));
+
+        // Check for a new Text widget with our error text.
+        Element errorElement = tester.findText(errorText(testValue));
+        expect(errorElement, isNotNull);
+      }
+
+      checkErrorText('Test');
+      checkErrorText('');
+    });
+  });
+}