重新定义的函数_buildGridCards(BuildContext context)可以在不传递BuildContext的情况下工作。出于什么原因被通过?因为我尝试时没有任何争论,但效果很好。即使代码运行良好,将BuildContext作为参数传递也有什么优势?
List<Card> _buildGridCards(int count) {
List<Card> cards = List.generate(
count,
(int index) => Card(
clipBehavior: Clip.antiAlias,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
AspectRatio(
aspectRatio: 18.0 / 11.0,
child: Image.asset('assets/diamond.png'),
),
Padding(
padding: EdgeInsets.fromLTRB(16.0, 12.0, 16.0, 8.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text('Title'),
SizedBox(height: 8.0),
Text('Secondary Text'),
],
),
),
],
),
),
);
return cards;
}
body: GridView.count(
crossAxisCount: 2,
padding: EdgeInsets.all(16.0),
childAspectRatio: 8.0 / 9.0,
children: _buildGridCards(10) // Replace
),
此后功能更改为:
List<Card> _buildGridCards(BuildContext context) {
List<Product> products = ProductsRepository.loadProducts(Category.all);
if (products == null || products.isEmpty) {
return const <Card>[];
}
final ThemeData theme = Theme.of(context);
final NumberFormat formatter = NumberFormat.simpleCurrency(
locale: Localizations.localeOf(context).toString());
return products.map((product) {
return Card(
clipBehavior: Clip.antiAlias,
// TODO: Adjust card heights (103)
child: Column(
// TODO: Center items on the card (103)
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
AspectRatio(
aspectRatio: 18 / 11,
child: Image.asset(
product.assetName,
package: product.assetPackage,
// TODO: Adjust the box size (102)
),
),
Expanded(
child: Padding(
padding: EdgeInsets.fromLTRB(16.0, 12.0, 16.0, 8.0),
child: Column(
// TODO: Align labels to the bottom and center (103)
crossAxisAlignment: CrossAxisAlignment.start,
// TODO: Change innermost Column (103)
children: <Widget>[
// TODO: Handle overflowing labels (103)
Text(
product.name,
style: theme.textTheme.title,
maxLines: 1,
),
SizedBox(height: 8.0),
Text(
formatter.format(product.price),
style: theme.textTheme.body2,
),
],
),
),
),
],
),
);
}).toList();
}
body: GridView.count(
crossAxisCount: 2,
padding: EdgeInsets.all(16.0),
childAspectRatio: 8.0 / 9.0,
children: _buildGridCards(context) // Changed code
),