What does layout builder do in Flutter?

mainAxisAlignment is how items are aligned on that axis. crossAxisAlignment is how items are aligned on the other axis .

The core of Flutter’s layout mechanism is widgets . In Flutter, almost everything is a widget—even layout models are widgets. The images, icons, and text that you see in a Flutter app are all widgets.

In Flutter, LayoutBuilder Widget is similar to the Builder widget except that the framework calls the builder function at layout time and provides the parent widget’s constraints. This is useful when the parent constrains the child’s size and doesn’t depend on the child’s intrinsic size .