将对齐方式更改为Alignment.center并使用EdgeInsets.zero对我来说工作得很好。

Container(
            height: 55,
            width: 55,
            decoration: const BoxDecoration(
              shape: BoxShape.circle,
              border: Border.symmetric(
                horizontal: BorderSide(
                  color: Colors.black,
                  width: 2.0,
                  style: BorderStyle.solid,
                ),
                vertical: BorderSide(
                  color: Colors.black,
                  width: 2.0,
                  style: BorderStyle.solid,
                ),
              ),
              boxShadow: [
                BoxShadow(
                  color: Colors.black,
                  offset: Offset(3.5, 3.5),
                  blurRadius: 0,
                  spreadRadius: -1,
                ),
              ],
            ),
            child: OutlinedButton(
              onPressed: () {
                /*  _controller.forward();
                          widget.onPress(); */
              },
              style: const ButtonStyle(
                alignment: Alignment.center,
                padding: MaterialStatePropertyAll(EdgeInsets.zero),
                backgroundColor: MaterialStatePropertyAll(Colors.white),
                shape: MaterialStatePropertyAll(CircleBorder()),
              ),
              child: const Icon(
                Icons.view_carousel_outlined,
                size: 35,
                color: Colors.black,
              ),
            ),
          ),

好的，所以我修复了它，基本上删除了容器中的很多样式，并在轮廓按钮本身中对边框进行了样式化。
下面是代码：

Container(
      decoration: const BoxDecoration(shape: BoxShape.circle, boxShadow: [
        BoxShadow(
          color: Colors.black,
          offset: Offset(3.5, 3.5),
          blurRadius: 0,
          spreadRadius: -1,
        ),
      ]),
      child: OutlinedButton(
        onPressed: () {
          _controller.forward();
          widget.onPress();
        },
        style: const ButtonStyle(
          side: MaterialStatePropertyAll(BorderSide(width: 2.0)),
          padding: MaterialStatePropertyAll(EdgeInsets.all(20.0)),
          backgroundColor: MaterialStatePropertyAll(Colors.white),
          shape: MaterialStatePropertyAll(CircleBorder()),
        ),
        child: const Icon(
          Icons.view_carousel_outlined,
          size: 35,
          color: Colors.black,
        ),
      ),
    ),

OutlinedButton有它自己的约束、边距、填充、tapTargetSize、visualDensity，因此，您的子对象在它内部不会居中。因此，要获得所需的UI代码段，请修改此属性或将图标居中并使用InkWell实现onTap（）功能
代码：

Container(
              height: 55,
              width: 55,
              decoration: const BoxDecoration(
                  color: Colors.white, //TODO: Add Color to Container
                  shape: BoxShape.circle,
                  border: Border.symmetric(
                    horizontal: BorderSide(
                      color: Colors.black,
                      width: 2.0,
                      style: BorderStyle.solid,
                    ),
                    vertical: BorderSide(
                      color: Colors.black,
                      width: 2.0,
                      style: BorderStyle.solid,
                    ),
                  ),
                  boxShadow: [
                    BoxShadow(
                      color: Colors.black,
                      offset: Offset(3.5, 3.5),
                      blurRadius: 0,
                      spreadRadius: -1,
                    ),
                  ]),
              child: InkWell( //TODO: Replace OutlinedButton with InkWell
                onTap: () {
                  _controller.forward();
                  widget.onPress();
                },
                child: const Center( //TODO: Wrap Icon with Center
                  child: Icon(
                    Icons.view_carousel_outlined,
                    // size: 35,
                    color: Colors.black,
                  ),
                ),
              ),
            ),

输出：