FloatingActionButton

const FloatingActionButton({
    Key key,
    this.child,
    this.tooltip,// 描述按下按钮时将发生的操作的文本。
    this.foregroundColor,// 按钮中图标和文本的默认前景色。
    this.backgroundColor,// 背景颜色
    this.focusColor,//当按钮具有输入焦点时用于填充按钮的颜色。
    this.hoverColor, //当指针悬停在按钮上时用于填充按钮的颜色
    this.splashColor,/ /此[FloatingActionButton]的[InkWell]的初始颜色。
    this.heroTag = const _DefaultHeroTag(),
    this.elevation,
    this.focusElevation,
    this.hoverElevation,
    this.highlightElevation,
    this.disabledElevation,
    @required this.onPressed,
    this.mini = false,
    this.shape, //按钮的[材质]形状
    this.clipBehavior = Clip.none,
    this.focusNode,
    this.autofocus = false,
    this.materialTapTargetSize,
    this.isExtended = false, // True if this is an "extended" floating action button.
  })