CSS 垂直居中。

1,display: table; display: table-cell

<div style="border:solid red 1px ;height:200px;width:200px;display: table;">
<div style="display: table-cell; vertical-align:middle; width:100%; text-align:center;"> Testaaaaaaaaaaaaaaaaaaa<br/>
Testaaaaaaaaaaaaaaaaaaa<br/>
</div>
</div>

display:flex;
flex-direction: row | row-reverse | column | column-reverse;
flex-wrap: nowrap | wrap | wrap-reverse;
flex-flow: <‘flex-direction’> || <‘flex-wrap’>
justify-content: flex-start | flex-end | center | space-between | space-around;
align-items: flex-start | flex-end | center | baseline | stretch;
align-content: flex-start | flex-end | center | space-between | space-around | stretch;
order: <integer>;
flex-grow: <number>;
flex-shrink: <number>; /* default 1 */
flex-basis: <length> | auto;
flex: none | [ <'flex-grow'> <'flex-shrink'>? || <'flex-basis'> ]
align-self: auto | flex-start | flex-end | center | baseline | stretch;