Flutter 自定义按钮

/// 登录按钮
  Widget buildLoginButtonWidget() {
    return Container(
      margin: EdgeInsets.only(top: 40, left: 16, right: 16),
      width: MediaQuery.of(context).size.width - 32,
      height: 50,
      decoration: BoxDecoration(
        color: Colors.transparent,
        image: DecorationImage(
            image: AssetImage('images/login_button.png'), fit: BoxFit.fill),
        borderRadius: BorderRadius.circular(25.0),
      ),
      child: FlatButton(
        onPressed: () {
        },
        child: Text("登录"),
        textColor: Colors.white,
        color: Colors.transparent, // 透明色
      )

    );
  }