NavigationToolbar constructor Null safety

const NavigationToolbar(
  1. {Key? key,
  2. Widget? leading,
  3. Widget? middle,
  4. Widget? trailing,
  5. bool centerMiddle,
  6. double middleSpacing}
)

Creates a widget that lays out its children in a manner suitable for a toolbar.

Implementation

const NavigationToolbar({
  Key? key,
  this.leading,
  this.middle,
  this.trailing,
  this.centerMiddle = true,
  this.middleSpacing = kMiddleSpacing,
}) : assert(centerMiddle != null),
     assert(middleSpacing != null),
     super(key: key);