还有另一种方法来做到这一点-只是使用FloatingActionButton适当的圆形按钮。

Scaffold(
      appBar: AppBar(
        title: const Text('Floating Action Button'),
      ),
      body: const Center(child: Text('Press the button below!')),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // Add your onPressed code here!
        },
        backgroundColor: Colors.green,
        child: const Icon(Icons.navigation),
      ),
    )

你可以使用下面的代码:

ElevatedButton(
      onPressed: () {},
      style: ElevatedButton.styleFrom(
        shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.all(Radius.circular(borderRadius))),
      ),
      child: Text("ok"),
    )

如果有人正在寻找完整的圆形按钮，那么我实现它的方式:

Center(
            child: SizedBox.fromSize(
              size: Size(80, 80), // Button width and height
              child: ClipOval(
                child: Material(
                  color: Colors.pink[300], // Button color
                  child: InkWell(
                    splashColor: Colors.yellow, // splash color
                    onTap: () {}, // Button pressed
                    child: Column(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: <Widget>[
                        Icon(Icons.linked_camera), // Icon
                        Text("Picture"), // Text
                      ],
                    ),
                  ),
                ),
              ),
            ),
          )

还有另一种方法来做到这一点-只是使用FloatingActionButton适当的圆形按钮。

Scaffold(
      appBar: AppBar(
        title: const Text('Floating Action Button'),
      ),
      body: const Center(child: Text('Press the button below!')),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // Add your onPressed code here!
        },
        backgroundColor: Colors.green,
        child: const Icon(Icons.navigation),
      ),
    )

要在按钮中使用任何形状，请确保执行button小部件内的所有代码:

 **shape: RoundedRectangleBorder(
        borderRadius: new BorderRadius.circular(18.0),
        side: BorderSide(color: Colors.red) ),**

如果你想让它变成正方形，使用BorderRadius.circular(0.0)，它会自动把它变成正方形。

按钮是这样的:

下面是给出UI屏幕的所有源代码:

 Scaffold(
    backgroundColor: Color(0xFF8E44AD),
    body: new Center(
      child: Column(
        children: <Widget>[
          Container(
            margin: EdgeInsets.fromLTRB(90, 10, 20, 0),
            padding: new EdgeInsets.only(top: 92.0),
            child: Text(
              "Currency Converter",
              style: TextStyle(
                fontSize: 48,
                fontWeight: FontWeight.bold,
                color: Colors.white,
              ),
            ),
          ),
          Container(
            margin: EdgeInsets.only(),
            padding: EdgeInsets.all(25),
            child: TextFormField(
              decoration: new InputDecoration(
                filled: true,
                fillColor: Colors.white,
                labelText: "Amount",
                border: OutlineInputBorder(
                  borderRadius: BorderRadius.circular(10),
                ),
              ),
            ),
          ),
          Container(
            padding: EdgeInsets.all(25),
            child: TextFormField(
              decoration: new InputDecoration(
                filled: true,
                fillColor: Colors.white,
                labelText: "From",
                border: OutlineInputBorder(
                  borderRadius: BorderRadius.circular(10),
                ),
              ),
            ),
          ),
          Container(
            padding: EdgeInsets.all(25),
            child: TextFormField(
              decoration: new InputDecoration(
                  filled: true,
                  fillColor: Colors.white,
                  labelText: "To",
                  border: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(10),
                  )),
            ),
          ),
          SizedBox(height: 20.0),
          MaterialButton(
            height: 58,
            minWidth: 340,
            shape: RoundedRectangleBorder(
                borderRadius: new BorderRadius.circular(12)),
            onPressed: () {},
            child: Text(
              "CONVERT",
              style: TextStyle(
                fontSize: 24,
                color: Colors.black,
              ),
            ),
            color: Color(0xFFF7CA18),
          ),
        ],
      ),
    ),
  ),
);

这里有另一个解决方案:

Container(
    height: MediaQuery.of(context).size.height * 0.10,
    width: MediaQuery.of(context).size.width,
    child: ButtonTheme(
        minWidth: MediaQuery.of(context).size.width * 0.75,
        child: RaisedButton(
            shape: RoundedRectangleBorder(
                borderRadius: new BorderRadius.circular(25.0),
                side: BorderSide(color: Colors.blue)),
                onPressed: () async {
                    // Do something
                },
                color: Colors.red[900],
                textColor: Colors.white,
                child: Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: Text("Button Text,
                    style: TextStyle(fontSize: 24)),
            ),
        ),
    ),
),