Material({Key key, MaterialType type: MaterialType.canvas, int elevation: 0, Color color, TextStyle textStyle, BorderRadius borderRadius, Widget child })

Creates a piece of material.

The type and the elevation arguments must not be null.

Source 

Material({
  Key key,
  this.type: MaterialType.canvas,
  this.elevation: 0,
  this.color,
  this.textStyle,
  this.borderRadius,
  this.child
}) : super(key: key) {
  assert(type != null);
  assert(elevation != null);
  assert(type != MaterialType.circle || borderRadius == null);
}