将crossAxisAlignment属性添加到您的Row;

crossAxisAlignment: CrossAxisAlignment.stretch

使用ButtonTheme和minWidth: double.infinity Package 允许提供约束

ButtonTheme(
  minWidth: double.infinity,
  child: MaterialButton(
    onPressed: () {},
    child: Text('Raised Button'),
  ),
),

或https://github.com/flutter/flutter/pull/19416着陆后

MaterialButton(
    onPressed: () {},
    child: SizedBox.expand(
      width: double.infinity, 
      child: Text('Raised Button'),
    ),
  ),

在Flutter 2.+中，考虑以下解决方案：

ElevatedButton(
  style: ElevatedButton.styleFrom(
    minimumSize: const Size(double.infinity, double.infinity), // <--- this line helped me
  ),
  onPressed: () {},
  child: Icon(
    Icons.keyboard_return
  ),
)

我们可以添加按钮内部容器。

解决方案：

Container(
            width: double.infinity,
            child: RaisedButton(
              onPressed: null,
              child: Text('NEXT'),
            ),
          )

你也可以试试
1.使用SizedBox

SizedBox(
  width: double.maxFinite, // set width to maxFinite
  child: RaisedButton(...),
)

1.使用MaterialButton的minWidth属性。

MaterialButton(
  minWidth: double.maxFinite, // set minWidth to maxFinite
  color: Colors.blue,
  onPressed: () {},
  child: Text("Button"),
)

可以在“子项：列”下插入
交叉轴对齐：CrossAxisAlignment.stretch
我的代码

我的结果

MaterialButton(
          minWidth: MediaQuery.of(context).size.width, // set minWidth to width of the device screen
          onPressed: () {},
          child: Text("Button"),
        )

供参考https://api.flutter.dev/flutter/widgets/MediaQuery-class.html

从文档和使用按钮主题与styleFrom实用程序静态方法，你可以这样写代码：

/// To specify buttons with a fixed width and the default height use
/// `fixedSize: Size.fromWidth(320)`. Similarly, to specify a fixed
/// height and the default width use `fixedSize: Size.fromHeight(100)`.
ElevatedButton(
          onPressed: () {},
          child: Text('text'),
          style: ElevatedButton.styleFrom(
      fixedSize: const Size.fromWidth(double.infinity),
    ),
  )

VisualDensity是你正在寻找的东西。将其添加到ButtonStyle对象。

ElevatedButton(
  style: const ButtonStyle(
    visualDensity: VisualDensity(
      horizontal: VisualDensity.maximumDensity,
      vertical: VisualDensity.maximumDensity,
    ),
  ),
  ...
),