android - 颤振破碎的 Apk

Question

我的问题是当我构建我的应用程序的 apk 时，按钮没有出现，你知道为什么吗？我留下的代码是开始屏幕。我无法测试它，因为我无法切换到其他屏幕，但是在 android studio 中使用模拟器时我没有任何问题。

class _mainmenuState extends State<mainmenu>{
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(backgroundColor: Colors. red ,title: Text("Main Menu"),titleTextStyle: TextStyle(fontFamily: 'Helvetica Neue',fontSize: 20)
        ),
        body: Stack(
          children: <Widget>[
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Positioned(top: 0, left: 0, child: button1()),
              ],
            ),
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Positioned(top: 0, left: 0, child: button2()),
              ],
            ),
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Positioned(top: 0, left: 0, child: button3()),
              ],
            ),
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Positioned(top: 0, left: 0, child: button4()),
              ],
            ),
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Positioned(top: 0, left: 0, child: button5()),
              ],
            ),
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Positioned(top: 0, left: 0, child: button6()),
              ],
            ),
          ],
        )
    );
  }
}

按钮的结构是相同的，所以我发送一个：

    [class button1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Align(
      alignment: AlignmentDirectional(-0.95, -0.66),
      child: ElevatedButton(
        child: const Text('LEGS',
            style: TextStyle(height: 1, fontSize: 14)
        ),

        onPressed: () {
          Navigator.push(
            context,
            MaterialPageRoute(
                builder: (context) => legsscreen()),
          );
        },
        style: ElevatedButton.styleFrom(
          minimumSize: Size(140.0, 47.0),
          shape: RoundedRectangleBorder( borderRadius: BorderRadius.only(topLeft: Radius.zero, topRight: Radius.circular(30), bottomLeft: Radius.zero, bottomRight: Radius.circular(30) ) ),
          primary: Colors.red,
        ),
      ),
    );
  }
}][1]