packages/flutter/test/material/dropdown_test.dart - external/github.com/flutter/flutter - Git at Google

 // Copyright 2015 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 'dart:math' as math;
 import 'dart:ui' show window;

 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

 import '../widgets/semantics_tester.dart';

 const List<String> menuItems = const <String>['one', 'two', 'three', 'four'];

 final Type dropdownButtonType = new DropdownButton<String>(
   onChanged: (_) { },
   items: const <DropdownMenuItem<String>>[]
 ).runtimeType;

 Widget buildFrame({
   Key buttonKey,
   String value = 'two',
   ValueChanged<String> onChanged,
   bool isDense = false,
   Widget hint,
   List<String> items = menuItems,
   Alignment alignment = Alignment.center,
   TextDirection textDirection = TextDirection.ltr,
 }) {
   return new TestApp(
     textDirection: textDirection,
     child: new Material(
       child: new Align(
         alignment: alignment,
         child: new DropdownButton<String>(
           key: buttonKey,
           value: value,
           hint: hint,
           onChanged: onChanged,
           isDense: isDense,
           items: items.map((String item) {
             return new DropdownMenuItem<String>(
               key: new ValueKey<String>(item),
               value: item,
               child: new Text(item, key: new ValueKey<String>(item + 'Text')),
             );
           }).toList(),
         ),
       ),
     ),
   );
 }

 class TestApp extends StatefulWidget {
   const TestApp({ this.textDirection, this.child });
   final TextDirection textDirection;
   final Widget child;
   @override
   _TestAppState createState() => new _TestAppState();
 }

 class _TestAppState extends State<TestApp> {
   @override
   Widget build(BuildContext context) {
     return new Localizations(
       locale: const Locale('en', 'US'),
       delegates: const <LocalizationsDelegate<dynamic>>[
         DefaultWidgetsLocalizations.delegate,
         DefaultMaterialLocalizations.delegate,
       ],
       child: new MediaQuery(
         data: new MediaQueryData.fromWindow(window),
         child: new Directionality(
           textDirection: widget.textDirection,
           child: new Navigator(
             onGenerateRoute: (RouteSettings settings) {
               assert(settings.name == '/');
               return new MaterialPageRoute<void>(
                 settings: settings,
                 builder: (BuildContext context) => widget.child,
               );
             },
           ),
         ),
       ),
     );
   }
 }

 // When the dropdown's menu is popped up, a RenderParagraph for the selected
 // menu's text item will appear both in the dropdown button and in the menu.
 // The RenderParagraphs should be aligned, i.e. they should have the same
 // size and location.
 void checkSelectedItemTextGeometry(WidgetTester tester, String value) {
   final List<RenderBox> boxes = tester.renderObjectList<RenderBox>(find.byKey(new ValueKey<String>(value + 'Text'))).toList();
   expect(boxes.length, equals(2));
   final RenderBox box0 = boxes[0];
   final RenderBox box1 = boxes[1];
   expect(box0.localToGlobal(Offset.zero), equals(box1.localToGlobal(Offset.zero)));
   expect(box0.size, equals(box1.size));
 }

 bool sameGeometry(RenderBox box1, RenderBox box2) {
   expect(box1.localToGlobal(Offset.zero), equals(box2.localToGlobal(Offset.zero)));
   expect(box1.size.height, equals(box2.size.height));
   return true;
 }

 void main() {
   testWidgets('Dropdown button control test', (WidgetTester tester) async {
     String value = 'one';
     void didChangeValue(String newValue) {
       value = newValue;
     }

     Widget build() => buildFrame(value: value, onChanged: didChangeValue);

     await tester.pumpWidget(build());

     await tester.tap(find.text('one'));
     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     expect(value, equals('one'));

     await tester.tap(find.text('three').last);

     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     expect(value, equals('three'));

     await tester.tap(find.text('three'));
     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     expect(value, equals('three'));

     await tester.pumpWidget(build());

     await tester.tap(find.text('two').last);

     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     expect(value, equals('two'));
   });

   testWidgets('Dropdown button with no app', (WidgetTester tester) async {
     String value = 'one';
     void didChangeValue(String newValue) {
       value = newValue;
     }

     Widget build() {
       return new Directionality(
         textDirection: TextDirection.ltr,
         child: new Navigator(
           initialRoute: '/',
           onGenerateRoute: (RouteSettings settings) {
             return new MaterialPageRoute<void>(
               settings: settings,
               builder: (BuildContext context) {
                 return new Material(
                   child: buildFrame(value: 'one', onChanged: didChangeValue),
                 );
               },
             );
           },
         ),
       );
     }

     await tester.pumpWidget(build());

     await tester.tap(find.text('one'));
     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     expect(value, equals('one'));

     await tester.tap(find.text('three').last);

     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     expect(value, equals('three'));

     await tester.tap(find.text('three'));
     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     expect(value, equals('three'));

     await tester.pumpWidget(build());

     await tester.tap(find.text('two').last);

     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     expect(value, equals('two'));
   });

   testWidgets('Dropdown in ListView', (WidgetTester tester) async {
     // Regression test for https://github.com/flutter/flutter/issues/12053
     // Positions a DropdownButton at the left and right edges of the screen,
     // forcing it to be sized down to the viewport width
     const String value = 'foo';
     final UniqueKey itemKey = new UniqueKey();
     await tester.pumpWidget(
       new MaterialApp(
         home: new Material(
           child: new ListView(
             children: <Widget>[
               new DropdownButton<String>(
                 value: value,
                 items: <DropdownMenuItem<String>>[
                   new DropdownMenuItem<String>(
                     key: itemKey,
                     value: value,
                     child: const Text(value),
                   ),
                 ],
                 onChanged: (_) {},
               ),
             ],
           ),
         ),
       ),
     );
     await tester.tap(find.text(value));
     await tester.pump();
     final List<RenderBox> itemBoxes = tester.renderObjectList<RenderBox>(find.byKey(itemKey)).toList();
     expect(itemBoxes[0].localToGlobal(Offset.zero).dx, equals(0.0));
     expect(itemBoxes[1].localToGlobal(Offset.zero).dx, equals(16.0));
     expect(itemBoxes[1].size.width, equals(800.0 - 16.0 * 2));
   });

   testWidgets('Dropdown screen edges', (WidgetTester tester) async {
     int value = 4;
     final List<DropdownMenuItem<int>> items = <DropdownMenuItem<int>>[];
     for (int i = 0; i < 20; ++i)
       items.add(new DropdownMenuItem<int>(value: i, child: new Text('$i')));

     void handleChanged(int newValue) {
       value = newValue;
     }

     final DropdownButton<int> button = new DropdownButton<int>(
       value: value,
       onChanged: handleChanged,
       items: items,
     );

     await tester.pumpWidget(
       new MaterialApp(
         home: new Material(
           child: new Align(
             alignment: Alignment.topCenter,
             child: button,
           ),
         ),
       ),
     );

     await tester.tap(find.text('4'));
     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     // We should have two copies of item 5, one in the menu and one in the
     // button itself.
     expect(tester.elementList(find.text('5')), hasLength(2));

     // We should only have one copy of item 19, which is in the button itself.
     // The copy in the menu shouldn't be in the tree because it's off-screen.
     expect(tester.elementList(find.text('19')), hasLength(1));

     expect(value, 4);
     await tester.tap(find.byWidget(button));
     expect(value, 4);
     // this waits for the route's completer to complete, which calls handleChanged
     await tester.idle();
     expect(value, 4);

     // TODO(abarth): Remove these calls to pump once navigator cleans up its
     // pop transitions.
     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation
   });

   for (TextDirection textDirection in TextDirection.values) {
     testWidgets('Dropdown button aligns selected menu item ($textDirection)', (WidgetTester tester) async {
       final Key buttonKey = new UniqueKey();
       const String value = 'two';

       Widget build() => buildFrame(buttonKey: buttonKey, value: value, textDirection: textDirection);

       await tester.pumpWidget(build());
       final RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
       assert(buttonBox.attached);
       final Offset buttonOriginBeforeTap = buttonBox.localToGlobal(Offset.zero);

       await tester.tap(find.text('two'));
       await tester.pump();
       await tester.pump(const Duration(seconds: 1)); // finish the menu animation

       // Tapping the dropdown button should not cause it to move.
       expect(buttonBox.localToGlobal(Offset.zero), equals(buttonOriginBeforeTap));

       // The selected dropdown item is both in menu we just popped up, and in
       // the IndexedStack contained by the dropdown button. Both of them should
       // have the same origin and height as the dropdown button.
       final List<RenderObject> itemBoxes = tester.renderObjectList(find.byKey(const ValueKey<String>('two'))).toList();
       expect(itemBoxes.length, equals(2));
       for (RenderBox itemBox in itemBoxes) {
         assert(itemBox.attached);
         assert(textDirection != null);
         switch (textDirection) {
           case TextDirection.rtl:
             expect(buttonBox.localToGlobal(buttonBox.size.bottomRight(Offset.zero)),
                    equals(itemBox.localToGlobal(itemBox.size.bottomRight(Offset.zero))));
             break;
           case TextDirection.ltr:
             expect(buttonBox.localToGlobal(Offset.zero), equals(itemBox.localToGlobal(Offset.zero)));
             break;
         }
         expect(buttonBox.size.height, equals(itemBox.size.height));
       }

       // The two RenderParagraph objects, for the 'two' items' Text children,
       // should have the same size and location.
       checkSelectedItemTextGeometry(tester, 'two');

       await tester.pumpWidget(new Container()); // reset test
     });
   }

   testWidgets('Dropdown button with isDense:true aligns selected menu item', (WidgetTester tester) async {
     final Key buttonKey = new UniqueKey();
     const String value = 'two';

     Widget build() => buildFrame(buttonKey: buttonKey, value: value, isDense: true);

     await tester.pumpWidget(build());
     final RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
     assert(buttonBox.attached);

     await tester.tap(find.text('two'));
     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     // The selected dropdown item is both in menu we just popped up, and in
     // the IndexedStack contained by the dropdown button. Both of them should
     // have the same vertical center as the button.
     final List<RenderBox> itemBoxes = tester.renderObjectList<RenderBox>(find.byKey(const ValueKey<String>('two'))).toList();
     expect(itemBoxes.length, equals(2));

     // When isDense is true, the button's height is reduced. The menu items'
     // heights are not.
     final double menuItemHeight = itemBoxes.map((RenderBox box) => box.size.height).reduce(math.max);
     expect(menuItemHeight, greaterThan(buttonBox.size.height));

     for (RenderBox itemBox in itemBoxes) {
       assert(itemBox.attached);
       final Offset buttonBoxCenter = buttonBox.size.center(buttonBox.localToGlobal(Offset.zero));
       final Offset itemBoxCenter = itemBox.size.center(itemBox.localToGlobal(Offset.zero));
       expect(buttonBoxCenter.dy, equals(itemBoxCenter.dy));
     }

     // The two RenderParagraph objects, for the 'two' items' Text children,
     // should have the same size and location.
     checkSelectedItemTextGeometry(tester, 'two');
   });

   testWidgets('Size of DropdownButton with null value', (WidgetTester tester) async {
     final Key buttonKey = new UniqueKey();
     String value;

     Widget build() => buildFrame(buttonKey: buttonKey, value: value);

     await tester.pumpWidget(build());
     final RenderBox buttonBoxNullValue = tester.renderObject(find.byKey(buttonKey));
     assert(buttonBoxNullValue.attached);


     value = 'three';
     await tester.pumpWidget(build());
     final RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
     assert(buttonBox.attached);

     // A Dropdown button with a null value should be the same size as a
     // one with a non-null value.
     expect(buttonBox.localToGlobal(Offset.zero), equals(buttonBoxNullValue.localToGlobal(Offset.zero)));
     expect(buttonBox.size, equals(buttonBoxNullValue.size));
   });

   testWidgets('Layout of a DropdownButton with null value', (WidgetTester tester) async {
     final Key buttonKey = new UniqueKey();
     String value;

     void onChanged(String newValue) {
       value = newValue;
     }

     Widget build() => buildFrame(buttonKey: buttonKey, value: value, onChanged: onChanged);

     await tester.pumpWidget(build());
     final RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
     assert(buttonBox.attached);

     // Show the menu.
     await tester.tap(find.byKey(buttonKey));
     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     // Tap on item 'one', which must appear over the button.
     await tester.tap(find.byKey(buttonKey));
     await tester.pump();
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation

     await tester.pumpWidget(build());
     expect(value, equals('one'));
   });

   testWidgets('Size of DropdownButton with null value and a hint', (WidgetTester tester) async {
     final Key buttonKey = new UniqueKey();
     String value;

     // The hint will define the dropdown's width
     Widget build() => buildFrame(buttonKey: buttonKey, value: value, hint: const Text('onetwothree'));

     await tester.pumpWidget(build());
     expect(find.text('onetwothree'), findsOneWidget);
     final RenderBox buttonBoxHintValue = tester.renderObject(find.byKey(buttonKey));
     assert(buttonBoxHintValue.attached);


     value = 'three';
     await tester.pumpWidget(build());
     final RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
     assert(buttonBox.attached);

     // A Dropdown button with a null value and a hint should be the same size as a
     // one with a non-null value.
     expect(buttonBox.localToGlobal(Offset.zero), equals(buttonBoxHintValue.localToGlobal(Offset.zero)));
     expect(buttonBox.size, equals(buttonBoxHintValue.size));
   });

   testWidgets('Dropdown menus must fit within the screen', (WidgetTester tester) async {

     // The dropdown menu isn't readily accessible. To find it we're assuming that it
     // contains a ListView and that it's an instance of _DropdownMenu.
     Rect getMenuRect() {
       Rect menuRect;
       tester.element(find.byType(ListView)).visitAncestorElements((Element element) {
         if (element.toString().startsWith('_DropdownMenu')) {
           final RenderBox box = element.findRenderObject();
           assert(box != null);
           menuRect = box.localToGlobal(Offset.zero) & box.size;
           return false;
         }
         return true;
       });
       assert(menuRect != null);
       return menuRect;
     }

     // In all of the tests that follow we're assuming that the dropdown menu
     // is horizontally aligned with the center of the dropdown button and padded
     // on the top, left, and right.
     const EdgeInsets buttonPadding = const EdgeInsets.only(top: 8.0, left: 16.0, right: 24.0);

     Rect getExpandedButtonRect() {
       final RenderBox box = tester.renderObject<RenderBox>(find.byType(dropdownButtonType));
       final Rect buttonRect = box.localToGlobal(Offset.zero) & box.size;
       return buttonPadding.inflateRect(buttonRect);
     }

     Rect buttonRect;
     Rect menuRect;

     Future<Null> popUpAndDown(Widget frame) async {
       await tester.pumpWidget(frame);
       await tester.tap(find.byType(dropdownButtonType));
       await tester.pumpAndSettle();
       menuRect = getMenuRect();
       buttonRect = getExpandedButtonRect();
       await tester.tap(find.byType(dropdownButtonType));
     }

     // Dropdown button is along the top of the app. The top of the menu is
     // aligned with the top of the expanded button and shifted horizontally
     // so that it fits within the frame.

     await popUpAndDown(
       buildFrame(alignment: Alignment.topLeft, value: menuItems.last)
     );
     expect(menuRect.topLeft, Offset.zero);
     expect(menuRect.topRight, new Offset(menuRect.width, 0.0));

     await popUpAndDown(
       buildFrame(alignment: Alignment.topCenter, value: menuItems.last)
     );
     expect(menuRect.topLeft, new Offset(buttonRect.left, 0.0));
     expect(menuRect.topRight, new Offset(buttonRect.right, 0.0));

     await popUpAndDown(
       buildFrame(alignment: Alignment.topRight, value: menuItems.last)
     );
     expect(menuRect.topLeft, new Offset(800.0 - menuRect.width, 0.0));
     expect(menuRect.topRight, const Offset(800.0, 0.0));

     // Dropdown button is along the middle of the app. The top of the menu is
     // aligned with the top of the expanded button (because the 1st item
     // is selected) and shifted horizontally so that it fits within the frame.

     await popUpAndDown(
       buildFrame(alignment: Alignment.centerLeft, value: menuItems.first)
     );
     expect(menuRect.topLeft, new Offset(0.0, buttonRect.top));
     expect(menuRect.topRight, new Offset(menuRect.width, buttonRect.top));

     await popUpAndDown(
       buildFrame(alignment: Alignment.center, value: menuItems.first)
     );
     expect(menuRect.topLeft, buttonRect.topLeft);
     expect(menuRect.topRight, buttonRect.topRight);

     await popUpAndDown(
       buildFrame(alignment: Alignment.centerRight, value: menuItems.first)
     );
     expect(menuRect.topLeft, new Offset(800.0 - menuRect.width, buttonRect.top));
     expect(menuRect.topRight, new Offset(800.0, buttonRect.top));

     // Dropdown button is along the bottom of the app. The bottom of the menu is
     // aligned with the bottom of the expanded button and shifted horizontally
     // so that it fits within the frame.

     await popUpAndDown(
       buildFrame(alignment: Alignment.bottomLeft, value: menuItems.first)
     );
     expect(menuRect.bottomLeft, const Offset(0.0, 600.0));
     expect(menuRect.bottomRight, new Offset(menuRect.width, 600.0));

     await popUpAndDown(
       buildFrame(alignment: Alignment.bottomCenter, value: menuItems.first)
     );
     expect(menuRect.bottomLeft, new Offset(buttonRect.left, 600.0));
     expect(menuRect.bottomRight, new Offset(buttonRect.right, 600.0));

     await popUpAndDown(
       buildFrame(alignment: Alignment.bottomRight, value: menuItems.first)
     );
     expect(menuRect.bottomLeft, new Offset(800.0 - menuRect.width, 600.0));
     expect(menuRect.bottomRight, const Offset(800.0, 600.0));
   });

   testWidgets('Dropdown menus are dismissed on screen orientation changes', (WidgetTester tester) async {
     await tester.pumpWidget(buildFrame());
     await tester.tap(find.byType(dropdownButtonType));
     await tester.pumpAndSettle();
     expect(find.byType(ListView), findsOneWidget);

     window.onMetricsChanged();
     await tester.pump();
     expect(find.byType(ListView, skipOffstage: false), findsNothing);
   });


   testWidgets('Semantics Tree contains only selected element', (WidgetTester tester) async {
     final SemanticsTester semantics = new SemanticsTester(tester);
     await tester.pumpWidget(buildFrame(items: menuItems));

     expect(semantics, isNot(includesNodeWith(label: menuItems[0])));
     expect(semantics, includesNodeWith(label: menuItems[1]));
     expect(semantics, isNot(includesNodeWith(label: menuItems[2])));
     expect(semantics, isNot(includesNodeWith(label: menuItems[3])));

     semantics.dispose();
   });
 }
	// Copyright 2015 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 'dart:math' as math;
	import 'dart:ui' show window;

	import 'package:flutter_test/flutter_test.dart';
	import 'package:flutter/material.dart';
	import 'package:flutter/rendering.dart';

	import '../widgets/semantics_tester.dart';

	const List<String> menuItems = const <String>['one', 'two', 'three', 'four'];

	final Type dropdownButtonType = new DropdownButton<String>(
	onChanged: (_) { },
	items: const <DropdownMenuItem<String>>[]
	).runtimeType;

	Widget buildFrame({
	Key buttonKey,
	String value = 'two',
	ValueChanged<String> onChanged,
	bool isDense = false,
	Widget hint,
	List<String> items = menuItems,
	Alignment alignment = Alignment.center,
	TextDirection textDirection = TextDirection.ltr,
	}) {
	return new TestApp(
	textDirection: textDirection,
	child: new Material(
	child: new Align(
	alignment: alignment,
	child: new DropdownButton<String>(
	key: buttonKey,
	value: value,
	hint: hint,
	onChanged: onChanged,
	isDense: isDense,
	items: items.map((String item) {
	return new DropdownMenuItem<String>(
	key: new ValueKey<String>(item),
	value: item,
	child: new Text(item, key: new ValueKey<String>(item + 'Text')),
	);
	}).toList(),
	),
	),
	),
	);
	}

	class TestApp extends StatefulWidget {
	const TestApp({ this.textDirection, this.child });
	final TextDirection textDirection;
	final Widget child;
	@override
	_TestAppState createState() => new _TestAppState();
	}

	class _TestAppState extends State<TestApp> {
	@override
	Widget build(BuildContext context) {
	return new Localizations(
	locale: const Locale('en', 'US'),
	delegates: const <LocalizationsDelegate<dynamic>>[
	DefaultWidgetsLocalizations.delegate,
	DefaultMaterialLocalizations.delegate,
	],
	child: new MediaQuery(
	data: new MediaQueryData.fromWindow(window),
	child: new Directionality(
	textDirection: widget.textDirection,
	child: new Navigator(
	onGenerateRoute: (RouteSettings settings) {
	assert(settings.name == '/');
	return new MaterialPageRoute<void>(
	settings: settings,
	builder: (BuildContext context) => widget.child,
	);
	},
	),
	),
	),
	);
	}
	}

	// When the dropdown's menu is popped up, a RenderParagraph for the selected
	// menu's text item will appear both in the dropdown button and in the menu.
	// The RenderParagraphs should be aligned, i.e. they should have the same
	// size and location.
	void checkSelectedItemTextGeometry(WidgetTester tester, String value) {
	final List<RenderBox> boxes = tester.renderObjectList<RenderBox>(find.byKey(new ValueKey<String>(value + 'Text'))).toList();
	expect(boxes.length, equals(2));
	final RenderBox box0 = boxes[0];
	final RenderBox box1 = boxes[1];
	expect(box0.localToGlobal(Offset.zero), equals(box1.localToGlobal(Offset.zero)));
	expect(box0.size, equals(box1.size));
	}

	bool sameGeometry(RenderBox box1, RenderBox box2) {
	expect(box1.localToGlobal(Offset.zero), equals(box2.localToGlobal(Offset.zero)));
	expect(box1.size.height, equals(box2.size.height));
	return true;
	}

	void main() {
	testWidgets('Dropdown button control test', (WidgetTester tester) async {
	String value = 'one';
	void didChangeValue(String newValue) {
	value = newValue;
	}

	Widget build() => buildFrame(value: value, onChanged: didChangeValue);

	await tester.pumpWidget(build());

	await tester.tap(find.text('one'));
	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	expect(value, equals('one'));

	await tester.tap(find.text('three').last);

	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	expect(value, equals('three'));

	await tester.tap(find.text('three'));
	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	expect(value, equals('three'));

	await tester.pumpWidget(build());

	await tester.tap(find.text('two').last);

	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	expect(value, equals('two'));
	});

	testWidgets('Dropdown button with no app', (WidgetTester tester) async {
	String value = 'one';
	void didChangeValue(String newValue) {
	value = newValue;
	}

	Widget build() {
	return new Directionality(
	textDirection: TextDirection.ltr,
	child: new Navigator(
	initialRoute: '/',
	onGenerateRoute: (RouteSettings settings) {
	return new MaterialPageRoute<void>(
	settings: settings,
	builder: (BuildContext context) {
	return new Material(
	child: buildFrame(value: 'one', onChanged: didChangeValue),
	);
	},
	);
	},
	),
	);
	}

	await tester.pumpWidget(build());

	await tester.tap(find.text('one'));
	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	expect(value, equals('one'));

	await tester.tap(find.text('three').last);

	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	expect(value, equals('three'));

	await tester.tap(find.text('three'));
	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	expect(value, equals('three'));

	await tester.pumpWidget(build());

	await tester.tap(find.text('two').last);

	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	expect(value, equals('two'));
	});

	testWidgets('Dropdown in ListView', (WidgetTester tester) async {
	// Regression test for https://github.com/flutter/flutter/issues/12053
	// Positions a DropdownButton at the left and right edges of the screen,
	// forcing it to be sized down to the viewport width
	const String value = 'foo';
	final UniqueKey itemKey = new UniqueKey();
	await tester.pumpWidget(
	new MaterialApp(
	home: new Material(
	child: new ListView(
	children: <Widget>[
	new DropdownButton<String>(
	value: value,
	items: <DropdownMenuItem<String>>[
	new DropdownMenuItem<String>(
	key: itemKey,
	value: value,
	child: const Text(value),
	),
	],
	onChanged: (_) {},
	),
	],
	),
	),
	),
	);
	await tester.tap(find.text(value));
	await tester.pump();
	final List<RenderBox> itemBoxes = tester.renderObjectList<RenderBox>(find.byKey(itemKey)).toList();
	expect(itemBoxes[0].localToGlobal(Offset.zero).dx, equals(0.0));
	expect(itemBoxes[1].localToGlobal(Offset.zero).dx, equals(16.0));
	expect(itemBoxes[1].size.width, equals(800.0 - 16.0 * 2));
	});

	testWidgets('Dropdown screen edges', (WidgetTester tester) async {
	int value = 4;
	final List<DropdownMenuItem<int>> items = <DropdownMenuItem<int>>[];
	for (int i = 0; i < 20; ++i)
	items.add(new DropdownMenuItem<int>(value: i, child: new Text('$i')));

	void handleChanged(int newValue) {
	value = newValue;
	}

	final DropdownButton<int> button = new DropdownButton<int>(
	value: value,
	onChanged: handleChanged,
	items: items,
	);

	await tester.pumpWidget(
	new MaterialApp(
	home: new Material(
	child: new Align(
	alignment: Alignment.topCenter,
	child: button,
	),
	),
	),
	);

	await tester.tap(find.text('4'));
	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	// We should have two copies of item 5, one in the menu and one in the
	// button itself.
	expect(tester.elementList(find.text('5')), hasLength(2));

	// We should only have one copy of item 19, which is in the button itself.
	// The copy in the menu shouldn't be in the tree because it's off-screen.
	expect(tester.elementList(find.text('19')), hasLength(1));

	expect(value, 4);
	await tester.tap(find.byWidget(button));
	expect(value, 4);
	// this waits for the route's completer to complete, which calls handleChanged
	await tester.idle();
	expect(value, 4);

	// TODO(abarth): Remove these calls to pump once navigator cleans up its
	// pop transitions.
	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation
	});

	for (TextDirection textDirection in TextDirection.values) {
	testWidgets('Dropdown button aligns selected menu item ($textDirection)', (WidgetTester tester) async {
	final Key buttonKey = new UniqueKey();
	const String value = 'two';

	Widget build() => buildFrame(buttonKey: buttonKey, value: value, textDirection: textDirection);

	await tester.pumpWidget(build());
	final RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
	assert(buttonBox.attached);
	final Offset buttonOriginBeforeTap = buttonBox.localToGlobal(Offset.zero);

	await tester.tap(find.text('two'));
	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	// Tapping the dropdown button should not cause it to move.
	expect(buttonBox.localToGlobal(Offset.zero), equals(buttonOriginBeforeTap));

	// The selected dropdown item is both in menu we just popped up, and in
	// the IndexedStack contained by the dropdown button. Both of them should
	// have the same origin and height as the dropdown button.
	final List<RenderObject> itemBoxes = tester.renderObjectList(find.byKey(const ValueKey<String>('two'))).toList();
	expect(itemBoxes.length, equals(2));
	for (RenderBox itemBox in itemBoxes) {
	assert(itemBox.attached);
	assert(textDirection != null);
	switch (textDirection) {
	case TextDirection.rtl:
	expect(buttonBox.localToGlobal(buttonBox.size.bottomRight(Offset.zero)),
	equals(itemBox.localToGlobal(itemBox.size.bottomRight(Offset.zero))));
	break;
	case TextDirection.ltr:
	expect(buttonBox.localToGlobal(Offset.zero), equals(itemBox.localToGlobal(Offset.zero)));
	break;
	}
	expect(buttonBox.size.height, equals(itemBox.size.height));
	}

	// The two RenderParagraph objects, for the 'two' items' Text children,
	// should have the same size and location.
	checkSelectedItemTextGeometry(tester, 'two');

	await tester.pumpWidget(new Container()); // reset test
	});
	}

	testWidgets('Dropdown button with isDense:true aligns selected menu item', (WidgetTester tester) async {
	final Key buttonKey = new UniqueKey();
	const String value = 'two';

	Widget build() => buildFrame(buttonKey: buttonKey, value: value, isDense: true);

	await tester.pumpWidget(build());
	final RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
	assert(buttonBox.attached);

	await tester.tap(find.text('two'));
	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	// The selected dropdown item is both in menu we just popped up, and in
	// the IndexedStack contained by the dropdown button. Both of them should
	// have the same vertical center as the button.
	final List<RenderBox> itemBoxes = tester.renderObjectList<RenderBox>(find.byKey(const ValueKey<String>('two'))).toList();
	expect(itemBoxes.length, equals(2));

	// When isDense is true, the button's height is reduced. The menu items'
	// heights are not.
	final double menuItemHeight = itemBoxes.map((RenderBox box) => box.size.height).reduce(math.max);
	expect(menuItemHeight, greaterThan(buttonBox.size.height));

	for (RenderBox itemBox in itemBoxes) {
	assert(itemBox.attached);
	final Offset buttonBoxCenter = buttonBox.size.center(buttonBox.localToGlobal(Offset.zero));
	final Offset itemBoxCenter = itemBox.size.center(itemBox.localToGlobal(Offset.zero));
	expect(buttonBoxCenter.dy, equals(itemBoxCenter.dy));
	}

	// The two RenderParagraph objects, for the 'two' items' Text children,
	// should have the same size and location.
	checkSelectedItemTextGeometry(tester, 'two');
	});

	testWidgets('Size of DropdownButton with null value', (WidgetTester tester) async {
	final Key buttonKey = new UniqueKey();
	String value;

	Widget build() => buildFrame(buttonKey: buttonKey, value: value);

	await tester.pumpWidget(build());
	final RenderBox buttonBoxNullValue = tester.renderObject(find.byKey(buttonKey));
	assert(buttonBoxNullValue.attached);


	value = 'three';
	await tester.pumpWidget(build());
	final RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
	assert(buttonBox.attached);

	// A Dropdown button with a null value should be the same size as a
	// one with a non-null value.
	expect(buttonBox.localToGlobal(Offset.zero), equals(buttonBoxNullValue.localToGlobal(Offset.zero)));
	expect(buttonBox.size, equals(buttonBoxNullValue.size));
	});

	testWidgets('Layout of a DropdownButton with null value', (WidgetTester tester) async {
	final Key buttonKey = new UniqueKey();
	String value;

	void onChanged(String newValue) {
	value = newValue;
	}

	Widget build() => buildFrame(buttonKey: buttonKey, value: value, onChanged: onChanged);

	await tester.pumpWidget(build());
	final RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
	assert(buttonBox.attached);

	// Show the menu.
	await tester.tap(find.byKey(buttonKey));
	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	// Tap on item 'one', which must appear over the button.
	await tester.tap(find.byKey(buttonKey));
	await tester.pump();
	await tester.pump(const Duration(seconds: 1)); // finish the menu animation

	await tester.pumpWidget(build());
	expect(value, equals('one'));
	});

	testWidgets('Size of DropdownButton with null value and a hint', (WidgetTester tester) async {
	final Key buttonKey = new UniqueKey();
	String value;

	// The hint will define the dropdown's width
	Widget build() => buildFrame(buttonKey: buttonKey, value: value, hint: const Text('onetwothree'));

	await tester.pumpWidget(build());
	expect(find.text('onetwothree'), findsOneWidget);
	final RenderBox buttonBoxHintValue = tester.renderObject(find.byKey(buttonKey));
	assert(buttonBoxHintValue.attached);


	value = 'three';
	await tester.pumpWidget(build());
	final RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
	assert(buttonBox.attached);

	// A Dropdown button with a null value and a hint should be the same size as a
	// one with a non-null value.
	expect(buttonBox.localToGlobal(Offset.zero), equals(buttonBoxHintValue.localToGlobal(Offset.zero)));
	expect(buttonBox.size, equals(buttonBoxHintValue.size));
	});

	testWidgets('Dropdown menus must fit within the screen', (WidgetTester tester) async {

	// The dropdown menu isn't readily accessible. To find it we're assuming that it
	// contains a ListView and that it's an instance of _DropdownMenu.
	Rect getMenuRect() {
	Rect menuRect;
	tester.element(find.byType(ListView)).visitAncestorElements((Element element) {
	if (element.toString().startsWith('_DropdownMenu')) {
	final RenderBox box = element.findRenderObject();
	assert(box != null);
	menuRect = box.localToGlobal(Offset.zero) & box.size;
	return false;
	}
	return true;
	});
	assert(menuRect != null);
	return menuRect;
	}

	// In all of the tests that follow we're assuming that the dropdown menu
	// is horizontally aligned with the center of the dropdown button and padded
	// on the top, left, and right.
	const EdgeInsets buttonPadding = const EdgeInsets.only(top: 8.0, left: 16.0, right: 24.0);

	Rect getExpandedButtonRect() {
	final RenderBox box = tester.renderObject<RenderBox>(find.byType(dropdownButtonType));
	final Rect buttonRect = box.localToGlobal(Offset.zero) & box.size;
	return buttonPadding.inflateRect(buttonRect);
	}

	Rect buttonRect;
	Rect menuRect;

	Future<Null> popUpAndDown(Widget frame) async {
	await tester.pumpWidget(frame);
	await tester.tap(find.byType(dropdownButtonType));
	await tester.pumpAndSettle();
	menuRect = getMenuRect();
	buttonRect = getExpandedButtonRect();
	await tester.tap(find.byType(dropdownButtonType));
	}

	// Dropdown button is along the top of the app. The top of the menu is
	// aligned with the top of the expanded button and shifted horizontally
	// so that it fits within the frame.

	await popUpAndDown(
	buildFrame(alignment: Alignment.topLeft, value: menuItems.last)
	);
	expect(menuRect.topLeft, Offset.zero);
	expect(menuRect.topRight, new Offset(menuRect.width, 0.0));

	await popUpAndDown(
	buildFrame(alignment: Alignment.topCenter, value: menuItems.last)
	);
	expect(menuRect.topLeft, new Offset(buttonRect.left, 0.0));
	expect(menuRect.topRight, new Offset(buttonRect.right, 0.0));

	await popUpAndDown(
	buildFrame(alignment: Alignment.topRight, value: menuItems.last)
	);
	expect(menuRect.topLeft, new Offset(800.0 - menuRect.width, 0.0));
	expect(menuRect.topRight, const Offset(800.0, 0.0));

	// Dropdown button is along the middle of the app. The top of the menu is
	// aligned with the top of the expanded button (because the 1st item
	// is selected) and shifted horizontally so that it fits within the frame.

	await popUpAndDown(
	buildFrame(alignment: Alignment.centerLeft, value: menuItems.first)
	);
	expect(menuRect.topLeft, new Offset(0.0, buttonRect.top));
	expect(menuRect.topRight, new Offset(menuRect.width, buttonRect.top));

	await popUpAndDown(
	buildFrame(alignment: Alignment.center, value: menuItems.first)
	);
	expect(menuRect.topLeft, buttonRect.topLeft);
	expect(menuRect.topRight, buttonRect.topRight);

	await popUpAndDown(
	buildFrame(alignment: Alignment.centerRight, value: menuItems.first)
	);
	expect(menuRect.topLeft, new Offset(800.0 - menuRect.width, buttonRect.top));
	expect(menuRect.topRight, new Offset(800.0, buttonRect.top));

	// Dropdown button is along the bottom of the app. The bottom of the menu is
	// aligned with the bottom of the expanded button and shifted horizontally
	// so that it fits within the frame.

	await popUpAndDown(
	buildFrame(alignment: Alignment.bottomLeft, value: menuItems.first)
	);
	expect(menuRect.bottomLeft, const Offset(0.0, 600.0));
	expect(menuRect.bottomRight, new Offset(menuRect.width, 600.0));

	await popUpAndDown(
	buildFrame(alignment: Alignment.bottomCenter, value: menuItems.first)
	);
	expect(menuRect.bottomLeft, new Offset(buttonRect.left, 600.0));
	expect(menuRect.bottomRight, new Offset(buttonRect.right, 600.0));

	await popUpAndDown(
	buildFrame(alignment: Alignment.bottomRight, value: menuItems.first)
	);
	expect(menuRect.bottomLeft, new Offset(800.0 - menuRect.width, 600.0));
	expect(menuRect.bottomRight, const Offset(800.0, 600.0));
	});

	testWidgets('Dropdown menus are dismissed on screen orientation changes', (WidgetTester tester) async {
	await tester.pumpWidget(buildFrame());
	await tester.tap(find.byType(dropdownButtonType));
	await tester.pumpAndSettle();
	expect(find.byType(ListView), findsOneWidget);

	window.onMetricsChanged();
	await tester.pump();
	expect(find.byType(ListView, skipOffstage: false), findsNothing);
	});


	testWidgets('Semantics Tree contains only selected element', (WidgetTester tester) async {
	final SemanticsTester semantics = new SemanticsTester(tester);
	await tester.pumpWidget(buildFrame(items: menuItems));

	expect(semantics, isNot(includesNodeWith(label: menuItems[0])));
	expect(semantics, includesNodeWith(label: menuItems[1]));
	expect(semantics, isNot(includesNodeWith(label: menuItems[2])));
	expect(semantics, isNot(includesNodeWith(label: menuItems[3])));

	semantics.dispose();
	});
	}