direction property
The direction to use as the main axis.
For example, if direction is Axis.horizontal, the default, the children are placed adjacent to one another in a horizontal run until the available horizontal space is consumed, at which point a subsequent children are placed in a new run vertically adjacent to the previous run.
Implementation
Axis get direction => _direction;Implementation
set direction (Axis value) {
assert(value != null);
if (_direction == value)
return;
_direction = value;
markNeedsLayout();
}