一种:
top:50%; left:50%; transform:translate(50%,-50%);position: relative|absolute;
第二种:
display: flex;
background-color: gray;
justify-content:center;
align-items: center;
text-align: justify;
一种:
top:50%; left:50%; transform:translate(50%,-50%);position: relative|absolute;
第二种: