Flutter基础widgets教程-PopupMenuButton篇

1 PopupMenuButton

当菜单隐藏式，点击或调用onSelected时显示一个弹出式菜单列表。

2 构造函数 

PopupMenuButton({
    Key key,
    @required this.itemBuilder,
    this.initialValue,
    this.onSelected,
    this.onCanceled,
    this.tooltip,
    this.elevation = 8.0,
    this.padding = const EdgeInsets.all(8.0),
    this.child,
    this.icon,
    this.offset = Offset.zero,
})

3 常用属性 

3.1 itemBuilder：item子项

itemBuilder:<PopupMenuItem<String>>[],

3.2 initialValue：初始值，如果itemBuilder里该值，则会高亮显示

initialValue: 'value',

3.3 onSelected：选择其中一项时回调

onSelected:(String action) {}

3.4 onCanceled：点击空白处，不选择时回调

onCanceled: () {}

3.5 dtooltip：提示

tooltip: "长按提示",

3.6 elevation：Z轴阴影

elevation:8.0,

3.7 child：子控件，不能和icon都设置

child: Text("abc"),

3.8 icon：IconButton子控件， 不能和child都设置

icon: Image(image: 
  AssetImage("lib/assets/tabbar/search.png"),
),