List components ListView and GridView simple utility

(I) The horizontal and vertical components are simple and practical

1. In Android, if you are creating a list layout, to create an Adapter, you also need a ViewHolder in order to loop through the View. To display a list layout in Flutter, simply implement the ListView or GridView constructor

A, GridView horizontal list implementation, set scrollDirection to horizontal

B, Set scrollDirection to vertical

2. Display different types of items

Create a ListItem and declare two methods

Create a header display item that inherits ListItem

3. Create a display item that inherits ListItem

Create a ListView to add the implementation