[移动开发]flutter2.0 动态列表参数传递

处理动态加载列表 Andriod 飘红

1. 空安全问题

void main () => runApp(MyApp(
    items: List<String>.generate(100, (i) => "Item $i")
));

class MyApp extends StatelessWidget{
  final List<String> items;
  // 此处 Key 后面需要添加 ? 才能编译通过
  // 原因: 空安全（Sound null safety）是 Dart 2.12 中新增的一项特性.导致无法编译通过
  // 类型后面跟操作符 ? 表示当前变量可为null。
  MyApp({Key? key,required this.items}):super(key:key);
  @override
  Widget build(BuildContext context ){
    return MaterialApp(
      title:'ListView widget',
      home:Scaffold(
          body: ListView.builder(
              itemCount:items.length,
              itemBuilder:(context,index){
                return  ListTile(
                  title: Text('${items[index]}'),
                );
              }
          )
      ),
    );
  }
}

2. 2.0后 必填参数: @required => required

void main () => runApp(MyApp(
    items: List<String>.generate(100, (i) => "Item $i")
));

class MyApp extends StatelessWidget{
  final List<String> items;
  // @required  => required 
  MyApp({Key? key, required this.items}):super(key:key);
  @override
  Widget build(BuildContext context ){
    return MaterialApp(
      title:'ListView widget',
      home:Scaffold(
          body: ListView.builder(
              itemCount:items.length,
              itemBuilder:(context,index){
                return  ListTile(
                  title: Text('${items[index]}'),
                );
              }
          )
      ),
    );
  }
}