效果：
Wrap
A widget that displays its children in multiple horizontal or vertical runs.
一个可以横向或纵向显示的流式布局的widget
使用场景：一行显示不下需要换行的时候
源码
代码语言：javascript复制 Wrap({
Key key,
this.direction = Axis.horizontal,//方向
this.alignment = WrapAlignment.start,//对齐方式
this.spacing = 0.0,//子widget 横向的间隔
this.runAlignment = WrapAlignment.start,
this.runSpacing = 0.0,//当横向时子widget纵向的间隔
this.crossAxisAlignment = WrapCrossAlignment.start,
this.textDirection,//文本方向
this.verticalDirection = VerticalDirection.down,
List<Widget> children = const <Widget>[],//子widget
}) : super(key: key, children: children);示例
代码语言：javascript复制 Wrap(
spacing: 8.0, // gap between adjacent chips
runSpacing: 4.0, // gap between lines
children: <Widget>[
Chip( label: Text('Hamilton') ),
Chip( label: Text('Lafayette') ),
Chip( label: Text('Mulligan') ),
Chip( label: Text('Laurens') ),
],
)官方文档：https://api.flutter.dev/flutter/widgets/Wrap-class.html
