decoration property

The decoration to show around the text field.

By default, draws a horizontal line under the text field but can be configured to show an icon, label, hint text, and error text.

This decoration does not replace the ambient InputDecorationTheme. Instead, it is merged with it by InputDecoration.applyDefaults. Only the properties that are left null here take their value from the InputDecorationThemeData returned by InputDecorationTheme.of, which in turn defaults to ThemeData.inputDecorationTheme. So, for example, when the theme specifies a border, passing an InputDecoration that leaves InputDecoration.border null does not remove that border; pass InputBorder.none to opt out of it explicitly.

Specify null to remove the decoration entirely (including the extra padding introduced by the decoration to save space for the labels).