For this example, generate a list of 10,000 Strings using the
List.generate constructor.

2. Convert the data source into widgets

To display the list of strings, render each String as a widget
using ListView.builder().
In this example, display each String on its own line.

Interactive example

Children’s extent

To specify each item’s extent, you can use either itemExtent or prototypeItem.
Specifying either is more efficient than letting the children determine their own extent
because the scrolling machinery can make use of the foreknowledge of the children’s
extent to save work, for example when the scroll position changes drastically.

Place a floating app bar above a list

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