ion-app
Ionic4项目中我们可以使用Ionic4内容组件ion-app对项目进行布局。 ion-app官方文档地址:https://ionicframework.com/docs/api/appApp is a container element for an Ionic application. There should only be one
element per project. An app can have many Ionic components including menus, headers, content, and footers. The overlay components get appended to the
when they are presented.