当我将 MediaQuery.of(context).padding.top 与 appBar 一起使用时，它返回 0.0。 这是为什么？

Question

When I use MediaQuery.of(context).padding.top without the navBar in the widget tree then it returns me the actual true value.

Reloaded 1 of 529 libraries in 637ms.
I/flutter (31730): 24.0

But when I place the appBar into the widget tree then it returns me 0.0 only.

Reloaded 1 of 529 libraries in 764ms.
I/flutter (31730): 0.0

Can someone please help that why it is happening?

Answer 1

From this property's docs :

If you consumed this padding (eg by building a widget that envelops or accounts for this padding in its layout in such a way that children are no longer exposed to this padding), you should remove this padding for subsequent descendants in the widget tree by inserting a new MediaQuery widget using the MediaQuery.removePadding factory.

As the top padding is accounted for by the navBar, it is no longer exposed to widgets below it.

Answer 2

In my case, I passed the padding value. and I consumed the padding.top in my Page1.

  Widget build(BuildContext context) {
    final padding = MediaQuery.of(context).padding;
    return SafeArea(
      child: Scaffold(
        body: IndexedStack(
          children: [
            Page1(padding),
            Page2(),
            Page3(),
            Page4(),
          ],
        ),