创建圆角按钮的不同方法如下:

用ElevatedButton. stylefrom

ElevatedButton(
          style: ElevatedButton.styleFrom(
            shape: RoundedRectangleBorder(
              borderRadius: BorderRadius.circular(30.0),
            ),
          ),
          onPressed: () {},
          child:
              Text("Buy now".toUpperCase(), style: TextStyle(fontSize: 14)),
        ),

用ButtonStyle提升按钮

ElevatedButton(
          style: ButtonStyle(
              shape: MaterialStateProperty.all<RoundedRectangleBorder>(
                  RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(50.0),
          ))),
          onPressed: () {},
          child: Text("Submit".toUpperCase()),
        ),

圆形按钮的实际演示可以在下面的Dartpad链接中找到:

圆形按钮演示例子在达特pad

1. 解决方案概述

FlatButton和RaisedButton已弃用。

因此，你可以使用形状放在样式属性，为TextButton和ElevatedButton。

自Flutter 2.0以来有一些变化:

style:属性类型已更改为ButtonStyle shape:属性类型已更改为MaterialStateProperty<T>

2. 圆形的按钮

在style属性中存在shape属性:

style: ButtonStyle(
  shape: MaterialStateProperty.all<RoundedRectangleBorder>(
    RoundedRectangleBorder(
      borderRadius: BorderRadius.circular(18.0),
      side: BorderSide(color: Colors.red)
    )
  )
)

方形按钮

对于方形按钮，您可以使用ElevatedButton或添加其他方式:

style: ButtonStyle(
  shape: MaterialStateProperty.all<RoundedRectangleBorder>(
    RoundedRectangleBorder(
      borderRadius: BorderRadius.zero,
      side: BorderSide(color: Colors.red)
    )
  )
)

完整的示例

Row(
  mainAxisAlignment: MainAxisAlignment.end,
  children: [
    TextButton(
      child: Text(
        "Add to cart".toUpperCase(),
        style: TextStyle(fontSize: 14)
      ),
      style: ButtonStyle(
        padding: MaterialStateProperty.all<EdgeInsets>(EdgeInsets.all(15)),
        foregroundColor: MaterialStateProperty.all<Color>(Colors.red),
        shape: MaterialStateProperty.all<RoundedRectangleBorder>(
          RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(18.0),
            side: BorderSide(color: Colors.red)
          )
        )
      ),
      onPressed: () => null
    ),
    SizedBox(width: 10),
    ElevatedButton(
      child: Text(
        "Buy now".toUpperCase(),
        style: TextStyle(fontSize: 14)
      ),
      style: ButtonStyle(
        foregroundColor: MaterialStateProperty.all<Color>(Colors.white),
        backgroundColor: MaterialStateProperty.all<Color>(Colors.red),
        shape: MaterialStateProperty.all<RoundedRectangleBorder>(
          RoundedRectangleBorder(
            borderRadius: BorderRadius.zero,
            side: BorderSide(color: Colors.red)
          )
        )
      ),
      onPressed: () => null
    )
  ]
)

您可以使用ElevatedButton小部件。提升的按钮小部件有一个shape属性，您可以使用该属性，如下面的代码片段所示。

ElevatedButton(
      style: ButtonStyle(
          shape: MaterialStateProperty.all<RoundedRectangleBorder>(
              RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(18.0),
                  side: BorderSide(
                      color: Colors.teal, 
                      width: 2.0,
                  ),
              ),
          ),
      ),
      child: Text('Submit'),
      onPressed: () {},
),

你也可以使用ButtonTheme():

下面是示例代码

ButtonTheme(
    minWidth: 200.0,
    shape: RoundedRectangleBorder(
        borderRadius: BorderRadius.circular(18.0),
        side: BorderSide(color: Colors.green)),
    child: RaisedButton(
        elevation: 5.0,
        hoverColor: Colors.green,
        color: Colors.amber,
        child: Text(
            "Place Order",
            style: TextStyle(
                     color: Colors.white, fontWeight: FontWeight.bold),
        ),
        onPressed: () {},
    ),
),

2020年9月起，Flutter 1.22.0:

“RaisedButton”和“FlatButton”都已弃用。

最新的解决方案是使用新的按钮:

1. ElevatedButton:

代码:

ElevatedButton(
  child: Text("ElevatedButton"),
  onPressed: () => print("it's pressed"),
  style: ElevatedButton.styleFrom(
    primary: Colors.red,
    onPrimary: Colors.white,
    shape: RoundedRectangleBorder(
      borderRadius: BorderRadius.circular(32.0),
    ),
  ),
)

别忘了，还有一个.icon构造函数可以方便地添加图标:

ElevatedButton.icon(
  icon: Icon(Icons.thumb_up),
  label: Text("Like"),
  onPressed: () => print("it's pressed"),
  style: ElevatedButton.styleFrom(
    shape: RoundedRectangleBorder(
      borderRadius: BorderRadius.circular(32.0),
    ),
  ),
)

2. OutlinedButton:

代码:

OutlinedButton.icon(
  icon: Icon(Icons.star_outline),
  label: Text("OutlinedButton"),
  onPressed: () => print("it's pressed"),
  style: ElevatedButton.styleFrom(
    side: BorderSide(width: 2.0, color: Colors.blue),
    shape: RoundedRectangleBorder(
      borderRadius: BorderRadius.circular(32.0),
    ),
  ),
)

3. TextButton:

如果你不想要轮廓或颜色填充，你总是可以使用TextButton。

圆边颜色容器:

Container(
  decoration: BoxDecoration(
    borderRadius: BorderRadius.circular(10),
    border: Border.all(color: Colors.red),
  ),
  child: Text("Some Text"),
)