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绝对定位、固定定位及flex容器

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2023年02月09日 14:47:18367浏览

绝对定位、固定定位及flex容器

1. 绝对定位与固定定位,并描述联系与区别

1.1 绝对定位absolute

HTML代码

  1. <!DOCTYPE html>
  2. <html lang="en">
  3. <head>
  4. <meta charset="UTF-8" />
  5. <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  6. <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  7. <title>绝对定位及相对定位</title>
  8. </head>
  9. <body>
  10. <ul>
  11. <li class="relative">相对定位</li>
  12. <li class="absolute">绝对定位</li>
  13. </ul>
  14. <style>
  15. * {
  16. margin: 0;
  17. padding: 0;
  18. box-sizing: border-box;
  19. }
  20. body {
  21. border: 5px solid red;
  22. }
  23. ul {
  24. width: 400px;
  25. height: 300px;
  26. border: 5px solid blue;
  27. }
  28. ul li {
  29. height: 40px;
  30. border: 1px solid black;
  31. list-style: none;
  32. }
  33. ul li:first-child {
  34. background-color: blue;
  35. }
  36. ul li:last-child {
  37. background-color: yellow;
  38. }
  39. ul li.absolute {
  40. position: absolute;
  41. top: 70px;
  42. left: 20px;
  43. }
  44. /* ul li.relative {
  45. position: relative;
  46. top: 10px;
  47. left: 100px;
  48. } */
  49. </style>
  50. </body>
  51. </html>

页面演示效果:
绝对定位

1.2 相对定位

HTML代码

  1. <!DOCTYPE html>
  2. <html lang="en">
  3. <head>
  4. <meta charset="UTF-8" />
  5. <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  6. <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  7. <title>绝对定位及相对定位</title>
  8. </head>
  9. <body>
  10. <ul>
  11. <li class="relative">相对定位</li>
  12. <li class="absolute">绝对定位</li>
  13. </ul>
  14. <style>
  15. * {
  16. margin: 0;
  17. padding: 0;
  18. box-sizing: border-box;
  19. }
  20. body {
  21. border: 5px solid red;
  22. }
  23. ul {
  24. width: 400px;
  25. height: 300px;
  26. border: 5px solid blue;
  27. }
  28. ul li {
  29. height: 40px;
  30. border: 1px solid black;
  31. list-style: none;
  32. }
  33. ul li:first-child {
  34. background-color: blue;
  35. }
  36. ul li:last-child {
  37. background-color: yellow;
  38. }
  39. ul li.absolute {
  40. position: absolute;
  41. /* top: 70px; */
  42. /* left: 20px; */
  43. }
  44. ul li.relative {
  45. position: relative;
  46. top: 10px;
  47. left: 100px;
  48. }
  49. </style>
  50. </body>
  51. </html>

页面演示效果如下:
相对定位

2.flex容器、容器属性及项目属性

2.1 容器:

初始html代码及页面演示效果:
html代码

  1. <!DOCTYPE html>
  2. <html lang="en">
  3. <head>
  4. <meta charset="UTF-8" />
  5. <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  6. <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  7. <title>flex布局及常用元素</title>
  8. </head>
  9. <body>
  10. <div class="container">
  11. <div class="item">item1</div>
  12. <div class="item">item2</div>
  13. <div class="item">item3</div>
  14. </div>
  15. <style>
  16. .container {
  17. display: flex;
  18. width: 500px;
  19. height: 60px;
  20. border: 1px solid black;
  21. flex-flow: row nowrap;
  22. place-content: start;
  23. }
  24. .container .item {
  25. width: 100px;
  26. height: 30px;
  27. background-color: lightgreen;
  28. border: 1px solid red;
  29. text-align: center;
  30. }
  31. </style>
  32. </body>
  33. </html>

页面演示效果:

2.2容器属性

2.2.1 place-content: 项目在”主轴”上的排列方式

  1. 右端靠齐
    1. .container {
    2. display: flex;
    3. width: 500px;
    4. height: 60px;
    5. border: 1px solid black;
    6. flex-flow: row nowrap;
    7. place-content: end;
    8. }
  2. 二端对齐
    1. .container {
    2. display: flex;
    3. width: 500px;
    4. height: 60px;
    5. border: 1px solid black;
    6. flex-flow: row nowrap;
    7. place-content: space-between;
    8. }
  3. 分散对齐
    1. .container {
    2. display: flex;
    3. width: 500px;
    4. height: 60px;
    5. border: 1px solid black;
    6. flex-flow: row nowrap;
    7. place-content: space-around;
    8. }
  4. 平均对齐
    1. .container {
    2. display: flex;
    3. width: 500px;
    4. height: 60px;
    5. border: 1px solid black;
    6. flex-flow: row nowrap;
    7. place-content: space-evenly;
    8. }

    2.2.2 place-items: 项目在”交叉轴”上的排列方式

  5. 顶部对齐

    1. .container {
    2. display: flex;
    3. width: 500px;
    4. height: 100px;
    5. border: 1px solid black;
    6. flex-flow: row nowrap;
    7. place-content: start;
    8. place-items: start;
    9. }

  6. 底部对齐

    1. .container {
    2. display: flex;
    3. width: 500px;
    4. height: 100px;
    5. border: 1px solid black;
    6. flex-flow: row nowrap;
    7. place-content: start;
    8. place-items: end;
    9. }

  7. 中间对齐

    1. .container {
    2. display: flex;
    3. width: 500px;
    4. height: 100px;
    5. border: 1px solid black;
    6. flex-flow: row nowrap;
    7. place-content: start;
    8. place-items: center;
    9. }

    2.3 项目属性

    2.3.1 flex: 项目在”主轴”上的缩放比例与宽度

    flex: 放大比例 允许收缩 主轴空间

  8. flexflex: 0 1 auto;默认,不放大,但可以自动收缩 同flex:initial;
    1. <style>
    2. .container {
    3. display: flex;
    4. width: 500px;
    5. /* height: 100px; */
    6. border: 1px solid black;
    7. flex-flow: row nowrap;
    8. place-content: start;
    9. place-items: center;
    10. }
    11. .container .item {
    12. width: 100px;
    13. height: 150px;
    14. background-color: lightgreen;
    15. border: 1px solid red;
    16. text-align: center;
    17. flex: 0 1 auto;
    18. }
  9. flex: 1 1 auto;完全响应式,允许放大和自动收缩 同flex:1;
  10. flex: 0 0 auto;完全不响应 同flex:none;

2.3.2 place-self 某项目在”交叉轴”上的排列方式

1 .place-self: start; 顶对齐

  1. .container > .item:nth-of-type(2) {
  2. background-color: yellow;
  3. height: 50px;
  4. place-self: start;
  5. }

2 . place-self: end; 底对齐

3 . place-self: center;中间对齐

2.3.3 order: 项目在”主轴”上的排列顺序

默认每个项目的order = 0,至越大,排序越靠后(值也可为负值)
例如:将item2 order设为3

  1. .container > .item:nth-of-type(2) {
  2. background-color: yellow;
  3. height: 50px;
  4. place-self: end;
  5. order: 3;
  6. }

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