横幅
进入到Flutter 新建一个项目为横幅
// Copyright 2020 The Flutter team. 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/material.dart';
import 'package:gallery/l10n/gallery_localizations.dart';
enum BannerDemoAction {
reset,
showMultipleActions,
showLeading,
}
class BannerDemo extends StatefulWidget {
const BannerDemo();
@override
_BannerDemoState createState() => _BannerDemoState();
}
class _BannerDemoState extends State<BannerDemo> {
static const _itemCount = 20;
var _displayBanner = true;
var _showMultipleActions = true;
var _showLeading = true;
void handleDemoAction(BannerDemoAction action) {
setState(() {
switch (action) {
case BannerDemoAction.reset:
_displayBanner = true;
_showMultipleActions = true;
_showLeading = true;
break;
case BannerDemoAction.showMultipleActions:
_showMultipleActions = !_showMultipleActions;
break;
case BannerDemoAction.showLeading:
_showLeading = !_showLeading;
break;
}
});
}
@override
Widget build(BuildContext context) {
final colorScheme = Theme.of(context).colorScheme;
final banner = MaterialBanner(
content: Text(GalleryLocalizations.of(context).bannerDemoText),
leading: _showLeading
? CircleAvatar(
child: Icon(Icons.access_alarm, color: colorScheme.onPrimary),
backgroundColor: colorScheme.primary,
)
: null,
actions: [
FlatButton(
child: Text(GalleryLocalizations.of(context).signIn),
onPressed: () {
setState(() {
_displayBanner = false;
});
},
),
if (_showMultipleActions)
FlatButton(
child: Text(GalleryLocalizations.of(context).dismiss),
onPressed: () {
setState(() {
_displayBanner = false;
});
},
),
],
backgroundColor: colorScheme.background,
);
return Scaffold(
appBar: AppBar(
automaticallyImplyLeading: false,
title: Text(GalleryLocalizations.of(context).demoBannerTitle),
actions: [
PopupMenuButton<BannerDemoAction>(
onSelected: handleDemoAction,
itemBuilder: (context) => <PopupMenuEntry<BannerDemoAction>>[
PopupMenuItem<BannerDemoAction>(
value: BannerDemoAction.reset,
child:
Text(GalleryLocalizations.of(context).bannerDemoResetText),
),
const PopupMenuDivider(),
CheckedPopupMenuItem<BannerDemoAction>(
value: BannerDemoAction.showMultipleActions,
checked: _showMultipleActions,
child: Text(
GalleryLocalizations.of(context).bannerDemoMultipleText),
),
CheckedPopupMenuItem<BannerDemoAction>(
value: BannerDemoAction.showLeading,
checked: _showLeading,
child: Text(
GalleryLocalizations.of(context).bannerDemoLeadingText),
),
],
),
],
),
body: ListView.builder(
itemCount: _displayBanner ? _itemCount + 1 : _itemCount,
itemBuilder: (context, index) {
if (index == 0 && _displayBanner) {
return banner;
}
return ListTile(
title: Text(
GalleryLocalizations.of(context)
.starterAppDrawerItem(_displayBanner ? index : index + 1),
),
);
}),
);
}
}
一直提示我没有找到这个类包。奇怪
