flex佈局很靈活, 這種佈局咱們也能夠稱之爲彈性佈局, 彈性佈局的主要優點就是元素的寬或者高會自動補全;javascript
好比有兩個div,一個div的寬度爲100px, 想讓另一個div的佔據剩下的寬度:css
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> <style> body{ margin:0; } .box{ display:flex; flex-direction:row; } .box .child{ width:40px; background:#f00; } .box .child1{ flex:1; background:#0f0 } </style> </head> <body> <div class="box"> <div class="child">child</div> <div class="child1">child1</div> </div> </body> </html>
或者有兩個div,一個高度爲100px, 另一個高度自動補全當前界面下剩餘的高度:html
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> <style> html,body,.box{ height:100%; } body{ margin:0; } .box{ display:flex; flex-direction:column; } .box .child{ height:40px; background:#f00; } .box .child1{ flex:1; background:#0f0 } </style> </head> <body> <div class="box"> <div class="child">child</div> <div class="child1">child1</div> </div> </body> </html>
因此說flex佈局是很靈活, flex佈局沒出現以前,這種佈局很差實現, 只能經過-webkit-calc的方式, 或者使用javascript的方式動態修改元素的樣式,還有水平方向元素自動適應佈局等, 用了flex,css的佈局方式更加多樣化了;java
flex佈局也能夠實現未知寬高的元素自動居中, 之前用的比較多的居中佈局方式主要爲固定寬高的負margin居中:android
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> <style> html,body,.parent{ height:100%; } .parent{ justify-content:center;/*水平居中*/ align-items: center; /*垂直居中*/ display:-webkit-flex; /* flex-direction:排版方向 flex-wrap:若是寬度超出父級寬度, 是否折行 flex-flow:flex-direction和flex-wrap的縮寫 */ } .child{ } </style> </head> <body> <div class="parent"> <div class="child"> hehe </div> </div> </body> </html>
子元素css的樣式flex:auto或者flex:1的時候, 該子元素會自動適應當前寬高:css3
若是一個父元素爲flex佈局, 內部元素的寬度會根據各自的flex屬性值進行等比切分:web
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> <style> *{ margin:0; padding:0; } </style> </head> <body> <style> .box{ display:flex; flex-direction:row } .box .child{ flex:1; } .box .chi{ flex:3; } </style> <div class="box"> <div class="child"> child </div> <div class="chi"> chi, child佔用1/4的百分比, chi佔用3/4的百分比 </div> </div> <br> <br> <style> .box1{ display:flex; flex-direction:row; } .box1 .child{ width:40px; } .box1 .chi{ flex:1; } </style> <div class="box1"> <div class="child"> child </div> <div class="chi"> chi, child固定長度, chi自動適應 </div> </div> <br> <br> <style> .box2 { display:flex; flex-direction:row; } .box2 .child1{ width:40px; } .box2 .child2{ flex:auto; } .box2 .child3{ width:40px; } </style> <div class="box2"> <div class="child1">child1</div> <div class="child2">child2, 兩邊固定寬度, 中間自動適應</div> <div class="child3">child3</div> </div> </body> </html>
高度自動適應的demo:瀏覽器
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> <style> *{ margin:0; padding:0; } html,body,.box{ height:100%; } .box{ display:flex; flex-direction:column; } .box .header{ height:40px; background:#f00; } .box .bodyer{ flex:1; background:#0f0; } .box .footer{ height:40px; background:#00f; } </style> </head> <body> <div class="box"> <div class="header">header</div> <div class="bodyer">bodyer</div> <div class="footer">footer</div> </div> </body> </html>
經過flex佈局能夠模擬一個微信的聊天窗口:微信
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no"> <style> *{ margin:0; padding:0; } html,body,.box{ height:100%; } .box{ display:-webkit-flex; display:flex; flex-direction:column; font-family:"microsoft yahei"; font-size:18px; } .box .header{ height:40px; line-height:40px; text-align:center; background:#3498DB; color:#fff; } .box .body{ display: block; border-bottom:1px solid #eee; overflow:auto; flex:1; } .box .send-left { align-self:flex-end; margin-top:10px; position:relative; height:35px; background:#F8C301; border-radius:5px; /* 圓角 */ line-height:35px; margin-left:10px; padding:0 10px; float:left; } .box .send-left .arrow { position:absolute; top:5px; left:-15px; width:0; height:0; font-size:0; border:solid 8px; border-color:#fff #F8C301 #fff #fff; } .box .send { align-self:flex-end; margin-top:10px; position:relative; height:35px; background:#2ECC71; border-radius:5px; /* 圓角 */ line-height:35px; margin-right:10px; padding:0 10px; float:right; } .box .send .arrow { position:absolute; top:5px; right:-15px; width:0; height:0; font-size:0; border:solid 8px; border-color:#fff #fff #fff #2ECC71; } .box .clear{ clear:both; } .box .footer{ height:40px; line-height:40px; display:-webkit-flex; display:flex; } .box .footer input{ flex:auto; border:none; border-right:1px solid #eee; font-size:18px; padding-left:4px; } .box .footer button{ width:50px; font-size:18px; } </style> </head> <body> <!-- 容器屬性 flex-direction flex-wrap flex-flow justify-content align-items align-content 項目屬性: order flex-grow flex-shrink flex-basis flex align-self --> <div class="box"> <div class="header"> 消息 </div> <div class="body"> <div class="send-left"> hehe我喲我去 <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> hehe <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> hehe我喲我去 <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> 來啊, 哈哈 <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> 來啊, 哈哈 <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> 來啊, 哈哈 <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> 來啊, 哈哈 <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> 來啊, 哈哈 <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> 來啊, 哈哈 <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> 來啊, 哈哈 <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> 來啊, 哈哈 <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> 來啊, 哈哈 <div class="arrow"></div> </div> <div class="clear"></div> <div class="send"> 來啊, 哈哈 <div class="arrow"></div> </div> </div> <div class="footer"> <input type="text"> <button>發送</button> </div> </div> </body> <script> </script> </html>
android 4.4以上版本支持display:flex。低版本不支持。ide
安卓4.1,以及4.1如下不支持flex佈局, 必須考慮別的方案;
android的低版本沒法使用display:flex, 可是能夠使用display:box替代;
要記得加瀏覽器前綴, 兼容寫法以下:
display: -webkit-box; display: -moz-box; display: -webkit-flex; display: -ms-flexbox; display: flex;
caniuse:http://caniuse.com/#feat=flexbox
MDN:https://developer.mozilla.org/zh-CN/docs/Web/CSS/CSS_Flexible_Box_Layout/Using_CSS_flexible_boxes
ruanyifeng:http://www.ruanyifeng.com/blog/2015/07/flex-examples.html