Question

我正在做一个下拉菜单，当我单击drop-btn时我想打开它，我看了一个w3schools教程，为什么它不起作用？

我复制了所有教程，但我不知道为什么它不起作用

HTML（我仅更改了下拉ID和函数名）

CSS（我仅更改了大小和颜色）

function myFunction() {
  document.getElementById("myDropdown").classList.toggle("show");
}

window.onclick = function(event) {
  if (!event.target.matches('.dropbtn')) {
    var dropdowns = document.getElementsByClassName("dropdown-content");
    var i;
    for (i = 0; i < dropdowns.length; i++) {
      var openDropdown = dropdowns[i];
      if (openDropdown.classList.contains('show')) {
        openDropdown.classList.remove('show');
      }
    }
  }
}

.dropdown {
  float: right;
  margin-right: 115px;
  overflow: hidden;
}

.dropdown .dropbtn {
  font-size: 16px;
  border: none;
  outline: none;
  color: white;
  padding: 14px 16px;
  background-color: #ff0000;
  font-family: inherit;
  margin: 0;
}

.dropbtn:hover {
  cursor: pointer;
}

.dropdown:hover {
  background-color: #ff7b7b;
  text-decoration: none;
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: #ff0000 !important;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  z-index: 1;
  opacity: 0;
  -webkit-transition: opacity .3s ease-in;
  -moz-transition: opacity .3s ease-in;
  -o-transition: opacity .3s ease-in;
  transition: opacity .3 ease-in;
}

.dropdown-content a {
  float: none;
  color: black;
  padding: 14px 16px;
  text-decoration: none;
  display: block;
}

.dropdown-content a:hover {
  background-color: #ff7b7b;
}

.show {
  display: block;
  z-index: 11;
}

<div class="dropdown">
  <button class="dropbtn" onclick="myFunction()"><li class="fa fa-bars fa-2x"></li></button>
  <div class="dropdown-content" id="myDropdown">
    <a href="signup.php" style="color: white;">Signup</a>
    <a href="#" style="color: white;">Info</a>
    <a href="#" style="color: white;">Last news</a>
  </div>
</div>

如果我单击下拉列表btn则不起作用

Answer 1

考虑一个详细信息/摘要解决方案。更少的代码并且具有内置的下拉功能：

<details><summary>Items</summary>
<div onclick="">Item 1</div>
<div onclick="">Item 2</div>
<div onclick="">Item 3</div>
<div onclick="">Item 4</div>
</details>

NB：除Edge之外，所有浏览器均支持。

Answer 2

我只需很少更改即可更新您的代码，请尝试此操作，希望对您有所帮助。谢谢

function myFunction() {
  $('#myDropdown').toggleClass('show');
}

window.onclick = function(event) {
  if (!event.target.matches('.dropbtn')) {
    var dropdowns = document.getElementsByClassName("dropdown-content");
    var i;
    for (i = 0; i < dropdowns.length; i++) {
      var openDropdown = dropdowns[i];
      if (openDropdown.classList.contains('show')) {
        openDropdown.classList.remove('show');
      }
    }
  }
}

.dropdown {
  float: right;
  margin-right: 115px;
  overflow: hidden;
}

.dropdown .dropbtn {
  font-size: 16px;
  border: none;
  outline: none;
  color: white;
  padding: 14px 16px;
  background-color: #ff0000;
  font-family: inherit;
  margin: 0;
}

.dropbtn:hover {
  cursor: pointer;
}

.dropdown:hover {
  background-color: #ff7b7b;
  text-decoration: none;
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: #ff0000 !important;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  z-index: 1;
  opacity: 0;
  -webkit-transition: opacity .3s ease-in;
  -moz-transition: opacity .3s ease-in;
  -o-transition: opacity .3s ease-in;
  transition: opacity .3 ease-in;
}

.dropdown-content a {
  float: none;
  color: black;
  padding: 14px 16px;
  text-decoration: none;
  display: block;
}

.dropdown-content a:hover {
  background-color: #ff7b7b;
}

.show {
  display: block;
  opacity: 1;
  z-index: 11;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<div class="dropdown">
  <button class="dropbtn" onclick="myFunction()"><li class="fa fa-bars fa-2x"></li></button>
  <div class="dropdown-content" id="myDropdown">
    <a href="signup.php" style="color: white;">Signup</a>
    <a href="#" style="color: white;">Info</a>
    <a href="#" style="color: white;">Last news</a>
  </div>
</div>

Answer 3

您的代码很好，只需从此CSS中删除opacity:0：

 .dropdown-content {
  display: none;
  position: absolute;
  background-color: #ff0000 !important;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  z-index: 1;
  opacity: 0; //<----------------------------------delete this
  -webkit-transition: opacity .3s ease-in;
  -moz-transition: opacity .3s ease-in;
  -o-transition: opacity .3s ease-in;
  transition: opacity .3 ease-in;
}

您的项目正在显示，但是您看不到它们，因为它的不透明度为零。也不要在按钮内使用<li>。它产生了意想不到的结果，我不知道为什么。

function myFunction() {
  document.getElementById("myDropdown").classList.toggle("show");
}

window.onclick = function(event) {
  if (!event.target.matches('.dropbtn')) {
    var dropdowns = document.getElementsByClassName("dropdown-content");
    var i;
    for (i = 0; i < dropdowns.length; i++) {
      var openDropdown = dropdowns[i];
      if (openDropdown.classList.contains('show')) {
        openDropdown.classList.remove('show');
      }
    }
  }
}

.dropdown {
  float: right;
  margin-right: 115px;
  overflow: hidden;
}

.dropdown .dropbtn {
  font-size: 16px;
  border: none;
  outline: none;
  color: white;
  padding: 14px 16px;
  background-color: #ff0000;
  font-family: inherit;
  margin: 0;
}

.dropbtn:hover {
  cursor: pointer;
}

.dropdown:hover {
  background-color: #ff7b7b;
  text-decoration: none;
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: #ff0000 !important;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  z-index: 1;
  -webkit-transition: opacity .3s ease-in;
  -moz-transition: opacity .3s ease-in;
  -o-transition: opacity .3s ease-in;
  transition: opacity .3 ease-in;
}

.dropdown-content a {
  float: none;
  color: black;
  padding: 14px 16px;
  text-decoration: none;
  display: block;
}

.dropdown-content a:hover {
  background-color: #ff7b7b;
}

.show {
  display: block;
  z-index: 11;
}

<div class="dropdown">
  <button class="dropbtn" onclick="myFunction()">Menu</button>
  <div class="dropdown-content" id="myDropdown">
    <a href="signup.php" style="color: white;">Signup</a>
    <a href="#" style="color: white;">Info</a>
    <a href="#" style="color: white;">Last news</a>
  </div>
</div>

点击如何做一个下拉菜单

3 个答案: