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
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
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
