Bootstrap button drop-down menu example tutorial

This chapter will explain how to use the Bootstrap class to add a drop-down menu to a button. To add a drop-down menu to a button, simply place the button and drop-down menu in a .btn-group . You can also use to indicate that the button acts as a drop-down menu.

Previous words

The button-type drop-down menu is basically the same as the drop-down menu in appearance. The difference is that ordinary drop-down menus are block elements, while button drop-down menus are inline-block elements. This article will introduce the Bootstrap button drop-down menu in detail

Overview

The button drop-down menu is actually an ordinary drop-down menu. The only difference is the external container "div.dropdown" Changed to "div.btn-group", the display changed from block to inline-block

<div class="btn-group">
  <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">按钮式下拉菜单 <span class="caret"></span>
  </button>
  <ul class="dropdown-menu"><li><a href="#">Action</a></li><li><a href="#">Another action</a></li><li><a href="#">Something else here</a></li><li role="separator" class="divider"></li><li><a href="#">Separated link</a></li>
  </ul></div><div class="dropdown">
  <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">普通下拉菜单 <span class="caret"></span>
  </button>
  <ul class="dropdown-menu"><li><a href="#">Action</a></li><li><a href="#">Another action</a></li><li><a href="#">Something else here</a></li><li role="separator" class="divider"></li><li><a href="#">Separated link</a></li>
  </ul></div>

Pop up

Some menus need to pop up. For example, the menu is at the bottom of the page, and this menu happens to have a drop-down menu. In order to give users a better experience, the drop-down menu has to pop up. In the Bootstrap framework, a class name "dropup" is specially proposed for this effect. You only need to add this class name to "btn-group"

[Triangle]

　Button The default downward triangle is created by adding a "" tag element to the tag and naming it "caret"

　　按钮下拉菜单

This triangle is completely created by CSS code to achieve

.caret {
  display: inline-block;
  width: 0;
  height: 0;
  margin-left: 2px;
  vertical-align: middle;
  border-top: 4px solid;
  border-right: 4px solid transparent;
  border-left: 4px solid transparent;
}

In addition, the triangle "caret" in the button has been styled to a certain extent:

.btn .caret {
  margin-left: 0;
}.btn-lg .caret {
  border-width: 5px 5px 0;
  border-bottom-width: 0;
}.dropup .btn-lg .caret {
  border-width: 0 5px 5px;
}

If the triangle direction To display upward, you need to append the "dropup" class name to the ".btn-group" class. It can be seen that the difference between the upward triangle and the downward triangle: In fact, it changes the value of a border-bottom

.dropup .caret,
.navbar-fixed-bottom .dropdown .caret {
  content: "";
  border-top: 0;
  border-bottom: 4px solid;
}

<div class="btn-group dropup" style="margin-top:140px"><button class="btn btn-default dropdown-toggle" data-toggle="dropdown" type="button">按钮下拉菜单<span class="caret"></span></button><ul class="dropdown-menu"><li><a href="##">按钮下拉菜单项</a></li><li><a href="##">按钮下拉菜单项</a></li><li><a href="##">按钮下拉菜单项</a></li><li><a href="##">按钮下拉菜单项</a></li></ul></div>

Split

The split button drop-down menu is actually an artificial combination of buttons and The triangle is split, leaving only one separate button in the end

<div class="btn-group">
  <button type="button" class="btn">Action</button>
  <button type="button" class="btn dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"><span class="caret"></span>
  </button>
  <ul class="dropdown-menu"><li><a href="#">Action</a></li><li><a href="#">Another action</a></li><li><a href="#">Something else here</a></li><li role="separator" class="divider"></li><li><a href="#">Separated link</a></li>
  </ul></div>

##Size

Button drop-down The menu is suitable for buttons of all sizes, including btn-xs, btn-lg, btn-sm, etc. Of course, ordinary drop-down lists also support changing button sizes

<div class="btn-group">
  <button class="btn btn-default btn-xs dropdown-toggle" type="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Extra small button <span class="caret"></span>
  </button>
  <ul class="dropdown-menu"><li><a href="#">Action</a></li><li><a href="#">Another action</a></li><li><a href="#">Something else here</a></li>
  </ul></div><div class="btn-group">
  <button class="btn btn-default btn-lg dropdown-toggle" type="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Large button <span class="caret"></span>
  </button>
  <ul class="dropdown-menu"><li><a href="#">Action</a></li><li><a href="#">Another action</a></li><li><a href="#">Something else here</a></li>
  </ul></div><div class="btn-group">
  <button class="btn btn-default btn-sm dropdown-toggle" type="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">small button <span class="caret"></span>
  </button>
  <ul class="dropdown-menu"><li><a href="#">Action</a></li><li><a href="#">Another action</a></li><li><a href="#">Something else here</a></li>
  </ul></div>

Finally

For some extended usage of ordinary drop-down lists, such as dividers, dividers, alignment, menu item status, etc., button drop-down menus also support it. Therefore, I personally feel that it is a bit redundant to set up the button drop-down menu component in bootstrap. It is only the difference between block and inline-block, but there is no functional difference

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