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PopupMenuButton should lazily build menu items

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Previously, the client of PopupMenuButton needed to build all the menu times

when building the PopupMenuButton. This can get expensive if, for example, each
item in a scrollable list has a popup menu associated with it.

Now the client passes a builder function to the PopupMenuButton that gets
invoked only when its time to show the menu items.
This commit is contained in:
Adam Barth 2016-04-06 13:28:09 -07:00
parent b930f0d4ff
commit 7ab122e557
7 changed files with 20 additions and 14 deletions
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2
dev/benchmarks/complex_layout/lib/main.dart
View File

@ -101,7 +101,7 @@ class TopBarMenu extends StatelessWidget {
Widget build(BuildContext context) {
return new PopupMenuButton<String>(
onSelected: (String value) { print("Selected: $value"); },
items: <PopupMenuItem<String>>[
itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
new PopupMenuItem<String>(
value: "Friends",
child: new MenuItemWithIcon(Icons.people, "Friends", "5 new")

2
examples/material_gallery/lib/demo/flexible_space_demo.dart
View File

@ -110,7 +110,7 @@ class FlexibleSpaceDemoState extends State<FlexibleSpaceDemo> {
_appBarBehavior = value;
});
},
items: <PopupMenuItem<AppBarBehavior>>[
itemBuilder: (BuildContext context) => <PopupMenuItem<AppBarBehavior>>[
new PopupMenuItem<AppBarBehavior>(
value: AppBarBehavior.scroll,
child: new Text('AppBar scrolls away')

2
examples/material_gallery/lib/demo/leave_behind_demo.dart
View File

@ -134,7 +134,7 @@ class LeaveBehindDemoState extends State<LeaveBehindDemo> {
actions: <Widget>[
new PopupMenuButton<LeaveBehindDemoAction>(
onSelected: handleDemoAction,
items: <PopupMenuEntry<LeaveBehindDemoAction>>[
itemBuilder: (BuildContext context) => <PopupMenuEntry<LeaveBehindDemoAction>>[
new PopupMenuItem<LeaveBehindDemoAction>(
value: LeaveBehindDemoAction.reset,
child: new Text('Reset the list')

10
examples/material_gallery/lib/demo/menu_demo.dart
View File

@ -64,7 +64,7 @@ class MenuDemoState extends State<MenuDemo> {
actions: <Widget>[
new PopupMenuButton<String>(
onSelected: showMenuSelection,
items: <PopupMenuItem<String>>[
itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
new PopupMenuItem<String>(
value: 'AppBar Menu',
child: new Text('AppBar Menu')
@ -91,7 +91,7 @@ class MenuDemoState extends State<MenuDemo> {
title: new Text('An item with a context menu button'),
trailing: new PopupMenuButton<String>(
onSelected: showMenuSelection,
items: <PopupMenuItem<String>>[
itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
new PopupMenuItem<String>(
value: _simpleValue1,
child: new Text('Context menu item one')
@ -114,7 +114,7 @@ class MenuDemoState extends State<MenuDemo> {
title: new Text('An item with a sectioned menu'),
trailing: new PopupMenuButton<String>(
onSelected: showMenuSelection,
items: <PopupMenuEntry<String>>[
itemBuilder: (BuildContext context) => <PopupMenuEntry<String>>[
new PopupMenuItem<String>(
value: 'Preview',
child: new ListItem(
@ -157,7 +157,7 @@ class MenuDemoState extends State<MenuDemo> {
title: new Text('An item with a simple menu'),
subtitle: new Text(_simpleValue)
),
items: <PopupMenuItem<String>>[
itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
new PopupMenuItem<String>(
value: _simpleValue1,
child: new Text(_simpleValue1)
@ -178,7 +178,7 @@ class MenuDemoState extends State<MenuDemo> {
title: new Text('An item with a checklist menu'),
trailing: new PopupMenuButton<String>(
onSelected: showCheckedMenuSelections,
items: <PopupMenuItem<String>>[
itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
new CheckedPopupMenuItem<String>(
value: _checkedValue1,
checked: isChecked(_checkedValue1),

2
examples/material_gallery/lib/demo/scrollable_tabs_demo.dart
View File

@ -53,7 +53,7 @@ class ScrollableTabsDemoState extends State<ScrollableTabsDemo> {
actions: <Widget>[
new PopupMenuButton<TabsDemoStyle>(
onSelected: changeDemoStyle,
items: <PopupMenuItem<TabsDemoStyle>>[
itemBuilder: (BuildContext context) => <PopupMenuItem<TabsDemoStyle>>[
new PopupMenuItem<TabsDemoStyle>(
value: TabsDemoStyle.iconsAndText,
child: new Text('Icons and Text')

2
examples/stocks/lib/stock_home.dart
View File

@ -220,7 +220,7 @@ class StockHomeState extends State<StockHome> {
),
new PopupMenuButton<_StockMenuItem>(
onSelected: (_StockMenuItem value) { _handleStockMenu(context, value); },
items: <PopupMenuItem<_StockMenuItem>>[
itemBuilder: (BuildContext context) => <PopupMenuItem<_StockMenuItem>>[
new CheckedPopupMenuItem<_StockMenuItem>(
value: _StockMenuItem.autorefresh,
checked: _autorefresh,

14
packages/flutter/lib/src/material/popup_menu.dart
View File

@ -380,6 +380,9 @@ Future<dynamic/*=T*/> showMenu/*<T>*/({
/// its menu to be dismissed.
typedef void PopupMenuItemSelected<T>(T value);
/// Signature used by [PopupMenuButton] to lazily construct the items shown when the button is pressed.
typedef List<PopupMenuEntry<T>> PopupMenuItemBuilder<T>(BuildContext context);
/// Displays a menu when pressed and calls [onSelected] when the menu is dismissed
/// because an item was selected. The value passed to [onSelected] is the value of
/// the selected menu item. If child is null then a standard 'navigation/more_vert'
@ -387,15 +390,18 @@ typedef void PopupMenuItemSelected<T>(T value);
class PopupMenuButton<T> extends StatefulWidget {
PopupMenuButton({
Key key,
this.items,
this.itemBuilder,
this.initialValue,
this.onSelected,
this.tooltip: 'Show menu',
this.elevation: 8,
this.child
}) : super(key: key);
}) : super(key: key) {
assert(itemBuilder != null);
}
final List<PopupMenuEntry<T>> items;
/// Called when the button is pressed to create the items to show in the menu.
final PopupMenuItemBuilder<T> itemBuilder;
final T initialValue;
@ -420,7 +426,7 @@ class _PopupMenuButtonState<T> extends State<PopupMenuButton<T>> {
showMenu/*<T>*/(
context: context,
elevation: config.elevation,
items: config.items,
items: config.itemBuilder(context),
initialValue: config.initialValue,
position: new ModalPosition(
left: topLeft.x,