css布局 三个按钮一排显示如何居中对齐

将div的css设置为text-align:center;就可以了
<div style="width: 100%;height: 100px;background-color: darkblue;text-align:center;">
    <button style="width: 200px;">1</button>
    <button style="width:200px;">2</button>
    <button style="width:200px;">3</button>
</div>