Implement better synchronization between the state of the input widget and the keyboard IME

Also add an input widget API for the keyboard submit button

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

@@ -13,6 +13,7 @@ import 'theme.dart';
 export 'package:flutter/services.dart' show KeyboardType;
 
 typedef void StringValueChanged(String value);
+typedef void StringValueSubmitted(String value);
 
 // TODO(eseidel): This isn't right, it's 16px on the bottom:
 // http://www.google.com/design/spec/components/text-fields.html#text-fields-single-line-text-field
@@ -24,7 +25,8 @@ class Input extends Scrollable {
     this.initialValue: '',
     this.placeholder,
     this.onChanged,
-    this.keyboardType: KeyboardType.TEXT
+    this.keyboardType: KeyboardType.TEXT,
+    this.onSubmitted
   }) : super(
     key: key,
     initialScrollOffset: 0.0,
@@ -35,6 +37,7 @@ class Input extends Scrollable {
   final KeyboardType keyboardType;
   final String placeholder;
   final StringValueChanged onChanged;
+  final StringValueSubmitted onSubmitted;
 
   _InputState createState() => new _InputState();
 }
@@ -52,7 +55,8 @@ class _InputState extends ScrollableState<Input> {
     _value = config.initialValue;
     _editableValue = new EditableString(
       text: _value,
-      onUpdated: _handleTextUpdated
+      onUpdated: _handleTextUpdated,
+      onSubmitted: _handleTextSubmitted
     );
   }
 
@@ -66,12 +70,20 @@ class _InputState extends ScrollableState<Input> {
     }
   }
 
+  void _handleTextSubmitted() {
+    if (config.onSubmitted != null)
+      config.onSubmitted(_value);
+  }
+
   Widget buildContent(BuildContext context) {
     ThemeData themeData = Theme.of(context);
     bool focused = Focus.at(context, config);
 
     if (focused && !_keyboardHandle.attached) {
       _keyboardHandle = keyboard.show(_editableValue.stub, config.keyboardType);
+      _keyboardHandle.setText(_editableValue.text);
+      _keyboardHandle.setSelection(_editableValue.selection.start,
+                                   _editableValue.selection.end);
     } else if (!focused && _keyboardHandle.attached) {
       _keyboardHandle.release();
     }

packages/flutter/lib/src/services/keyboard.dart

@@ -77,6 +77,18 @@ class KeyboardHandle {
     assert(_keyboard._currentHandle != this);
   }
 
+  void setText(String text) {
+    assert(_attached);
+    assert(_keyboard._currentHandle == this);
+    _keyboard.service.setText(text);
+  }
+
+  void setSelection(int start, int end) {
+    assert(_attached);
+    assert(_keyboard._currentHandle == this);
+    _keyboard.service.setSelection(start, end);
+  }
+
 }
 
 final Keyboard keyboard = new Keyboard(_KeyboardConnection.instance.keyboardService);

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

@@ -14,6 +14,7 @@ import 'framework.dart';
 const _kCursorBlinkHalfPeriod = 500; // milliseconds
 
 typedef void StringUpdated();
+typedef void StringSubmitted();
 
 class TextRange {
   const TextRange({ this.start, this.end });
@@ -32,18 +33,22 @@ class TextRange {
 }
 
 class EditableString implements KeyboardClient {
+  EditableString({this.text: '', this.onUpdated, this.onSubmitted}) {
+    assert(onUpdated != null);
+    assert(onSubmitted != null);
+    stub = new KeyboardClientStub.unbound()..impl = this;
+    selection = new TextRange(start: text.length, end: text.length);
+  }
+
   String text;
   TextRange composing = const TextRange.empty();
-  TextRange selection = const TextRange.empty();
+  TextRange selection;
 
   final StringUpdated onUpdated;
+  final StringSubmitted onSubmitted;
 
   KeyboardClientStub stub;
 
-  EditableString({this.text: '', this.onUpdated}) {
-    stub = new KeyboardClientStub.unbound()..impl = this;
-  }
-
   String textBefore(TextRange range) {
     return text.substring(0, range.start);
   }
@@ -129,7 +134,9 @@ class EditableString implements KeyboardClient {
     onUpdated();
   }
 
-  void submit(SubmitAction action) {}
+  void submit(SubmitAction action) {
+    onSubmitted();
+  }
 }
 
 class EditableText extends StatefulComponent {

packages/unit/test/widget/input_test.dart

@@ -17,6 +17,10 @@ class MockKeyboard implements KeyboardService {
   void showByRequest() {}
 
   void hide() {}
+
+  void setText(String text) {}
+
+  void setSelection(int start, int end) {}
 }
 
 void main() {