flutter得Positioned失效

Question

flutter得Positioned出现不生效得情况

class stack_item extends StatelessWidget{


  BuildContext? get context => null;
  @override
  Widget build(BuildContext context){
    late final screenSize = MediaQuery.of(context!).size;
    late final screenW = screenSize.width;
    late final screenH = screenSize.height;
    print("h:$screenH,w:$screenW");
    return Container(
      width:screenW
      ,height:screenH,
      child:Scaffold(
      body: Stack(
        fit: StackFit.expand,
        children: [
          Positioned(
              left:0.0,
              top: 0.0,
          child: NavShow(width_temp: screenW,height_temp: screenH,)),
          Positioned(bottom:0.0,left:0.0,child:nav_bottom_show(width_temp: screenW,height_temp: screenH,) ),
          Positioned(left: 0.5,bottom: 0.0,child: Sliders_item(width_temp: screenW,height_temp: screenH,),),
          Positioned(right: 0.2,top: 0.0,child: top_nav(width_temp: screenW,height_temp: screenH,),)
        ],
      )),
    );
  }
}

最后得组件中得top_nav出现了不生效得情况

也就右上角得蓝色区域没有发生位移

Answer 1

不明白你这个布局为什么要用到Positioned,不是简单的row和col就能做到了吗?