day18 review
Java-day19 study notes
day19
One, div and span tags
div是html中一个普通的标签，主要用来当做容器，一般用于配合css完成网页的基本布局,
span是html中一个普通的标签，一般作为文本容器
1.1 Difference
div是一个块级标签，独占一行，能存放所有内容（除了html、head和body）
span是一个行级标签，内容会在一行内追加，只能嵌套像文本、图片、超链接
Two, CSS
Cascading Style Sheets Cascading Style Sheets
Stacking: layer by layer
Style sheet: a collection of styles
Note: learning html is learning tags, learning CSS mainly learns styles (attributes), selectors
1.1 Role
1. 美化页面,修饰页面
2. 之前是html自己完成内容和样式，而现在我们可以通过css来完成样式的内容，并且可以批量的完成的样式的添加和修改
html当做毛坯房, CSS当做装修。
1.2 Why use CSS
之前的问题：
1. 之前用html属性完成样式的时候有很多问题，比如字体的大小只能在1和7之前选择，不能设置更大的字体，还有超链接的下换线不能去除等
2. 我们给标签设置属性之前需要先记忆标签是否有此属性，如果没有的话，写上也没有效果。
3. 有些效果需要嵌套好几层标签才能实现
而CSS可以解决如上问题
1. css不用记忆哪些属性属于哪个标签
2. 当需求变更时我们不需要修改大量的代码就可以满足需求
1.3 How to use
① Format
选择器 {
属性名1 : 属性值1;
属性名2 : 属性值2;
属性名3 : 属性值3
}
注意事项：
1. 属性名和属性值之间通过英文状态的 : 连接
2. 大括号中可以放多对属性名和属性值，但是它们之间要通过分号 ; 分隔
3. 最后一个属性名和属性值的后面可以不加 ;
② Where to put css to use [introduction method]
HTML is a language; CSS is also a language. If you want CSS to modify the style of HTML, you must introduce CSS into HTML. That is: to solve the problem of where to write the CSS code
行内样式
内部样式
外部样式
1.4 Introduction
① The first type: inline style [inline style] [understand]
把CSS代码内嵌到HTML代码里，直接通过标签的style属性进行设置
<p style="color: green;">我是文字</p>
② The second type: internal style [Master]
把CSS代码写在HTML文档内部,通过style标签来结合
1. 需要在head标签中写一个style标签
2. 在style标签中统一写css相关的样式设置
注意：
1. style标签中，可以写上type="text/css"，也可以不写
2. style标签，一定要放在head标签中
<style type="text/css">
p {
color: pink;
font-size: 50px
}
</style>
③ The third type: external style [master]
把CSS代码写在独立的CSS文件里,通过link标签结合
1. 将css样式写在一个后缀为css的文件中
2. 在html文件中引入css文件
注意：引入外部css文件，是在head标签中写一个link标签引入的
<link rel="stylesheet" href="../css/bb.css">
④ The priority of the three introduction methods
就近原则，也就是距离要修饰的标签最近的引入方式产生效果
1.5 selector
Selector: used to select HTML elements (tags) for style modification
① Basic selector
| Selector | description | grammar | Example |
|---|---|---|---|
| Label selector | Select tags based on HTML tag name | 标签名称{} |
div{ color:red; } |
| ID selector | Select label based on id attribute value | #id值{} |
#d1 { color:blue; } |
| Class selector | Select the label according to the class attribute value (class name) | .类名{} |
.c1 { color:yellow; } |
| Universal selector | Select all tags | *{} |
*{ color: pink;} |
② Selector priority
ID选择器 > 类选择器 > 标签选择器 > 通用选择器
注意：如果优先级相同，那么就满足就近原则
③ Extended selector
The combination of multiple basic selectors can select labels more flexibly
| Selector | description | grammar | Example |
|---|---|---|---|
| Level selector | Select tags based on HTML tag name | 祖先 后代 |
div a{ } |
| Attribute selector | Filter elements based on the value of the specified attribute | [属性='值'] |
input[type='text'] { } |
| Union selector | Combine the results of multiple selectors | 选择器1,选择器2,... |
.c1, span { } |
④ Pseudo-class selector [understand]
| Selector | description | Example |
|---|---|---|
:link |
Select the normal hyperlink | a:link{} |
:visited |
Select the hyperlinks that have been visited | a:visited{} |
:hover |
Select the hyperlink on mouseover | a:hover{} |
:active |
Select the hyperlink pressed by the mouse | a:active{} |
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>05-伪类选择器</title>
<style>
/*超链接默认的颜色*/
a:link{
color: blueviolet;
}
/*超链接被访问之后的颜色*/
a:visited{
color: mediumvioletred;
}
/*鼠标悬浮在超链接上方显示的颜色*/
a:hover{
color: green;
}
/*鼠标点击不松开的颜色*/
a:active{
color: pink;
}
/*注意：一定要确保顺序为lvha*/
</style>
</head>
<body>
<a href="https://www.baidu.com">百度一下，你就知道</a>
</body>
</html>
1.6 common attributes
CSS provides a large number of styles (attributes) to modify HTML tags. What we need to know are: background attributes, text styles, and font attributes.
① Background attributes
| Features | Attribute name | Attribute value |
|---|---|---|
| Background color | background-color |
1. Color constants, such as: red 2. Use hexadecimal, such as: #ABC 3. Use rgb for red, green, and blue (red, green, blue) |
| Background picture | background-image |
url(图片的路径) |
| Tiling | background-repeat |
repeatdefault. Background image will be repeated in the vertical and horizontal directions repeat-xbackground image will be repeated in the horizontal direction. repeat-yThe background image will repeat in the vertical direction. no-repeatThe background image will only be displayed once. |
② Text style
| Features | Attribute name | Attribute value |
|---|---|---|
| colour | color |
colour |
| Set row height | line-height |
Pixel |
| Text modification | text-decoration |
underlineUnderline overlinecrossed the ine-throughstrikeout nonedo not line |
| Text indent | text-indent |
For indenting text, you can use em units. |
| Text alignment | text-align |
leftArrange the text to the left. rightArrange the text to the right. centerArrange the text in the middle. Default value: Determined by the browser. |
③ Font attributes
| Features | Attribute name | effect |
|---|---|---|
| Font name | font-family |
Set the font, the machine must have this font |
| Set size | font-size |
Pixel |
| Set style | font-style |
italicItalic normalDefault value. The browser displays a standard font style. |
| Set thickness | font-weight |
boldBold |