Question

我有两个带浮动占位符的输入字段。在焦点上，占位符向上移动并为用户创建输入空间。但是一旦用户开始输入它就会消失。我希望占位符在文本框中键入内容后保持在同一位置。这只能使用CSS吗？

input {
  width: 100%;
  display: block;
  border: none;
  padding: 20px 0 10px 0;
  border-bottom: solid 1px #343a40;
  -webkit-transition: all 0.3s cubic-bezier(0.64, 0.09, 0.08, 1);
  transition: all 0.3s cubic-bezier(0.64, 0.09, 0.08, 1);
  background: -webkit-linear-gradient(top, rgba(255, 255, 255, 0) 99%, #007bff 1%);
  background: linear-gradient(to bottom, rgba(255, 255, 255, 0) 99%, #007bff 1%);
  background-position: -1000px 0;
  background-size: auto 100%;
  background-repeat: no-repeat;
  color: #000;
}

input:focus,
input:valid {
  box-shadow: none;
  outline: none;
  background-position: 0 0;
}

input::-webkit-input-placeholder {
  font-family: 'roboto', sans-serif;
  -webkit-transition: all 0.3s ease-in-out;
  transition: all 0.3s ease-in-out;
}

input:focus::-webkit-input-placeholder,
input:valid::-webkit-input-placeholder {
  color: #007bff;
  font-size: 12px;
  -webkit-transform: translateY(-20px);
  transform: translateY(-20px);
  visibility: visible !important;
}

<input placeholder="Username" type="text" required>
<input placeholder="Password" type="password" required>

Answer 1

如评论所述，您应该使用label。 也正确连接到其输入以保持连贯。

https://www.w3.org/wiki/HTML/Elements/label

<label>元素表示用户界面中的标题。


HTML属性 for = string


指定用于指示与标题关联的表单控件。   属性的值必须是与label元素在同一Document中的可标记表单关联元素的ID。

示例：<input type="checkbox" id="lost" name="lost"> <label for="lost">Lost</label>

从那里开始，在输入后设置label，它将通过+选择器设置样式。

CSS示例

label {
  position: absolute;
  margin-top: -1.75em;/*climbs under the input */
  transition: all 0.3s ease-in-out;
}
input {
  position: relative;
  z-index: 1;/* set input on top of label. opaque white bg color can be used to lighten label's color */
  width: 100%;
  display: block;
  border: none;
  padding: 20px 0 10px 0;
  border-bottom: solid 1px #343a40;
  transition: all 0.3s cubic-bezier(0.64, 0.09, 0.08, 1);
  transition: all 0.3s cubic-bezier(0.64, 0.09, 0.08, 1);
  background: linear-gradient(
    to top,
    rgba(255, 255, 255, 0) 99%,
    #007bff 1%
  );
  background: linear-gradient(to bottom, rgba(255, 255, 255, 0) 99%, #007bff 1%)
    rgba(255, 255, 255, 0.4);
  background-position: -1000px 0;
  background-size: auto 100%;
  background-repeat: no-repeat;
  color: transparent;/* hide value if any when label is standing here too */
}
input:focus {
  color: #000;
}
input:valid + label {
  color: #06a31b;
  z-index: 1;/* let's show this field is filled */
}
input:focus + label, input:active + label {
  font-size: 12px;
  color: #007bff;
  font-size: 12px;
  transform: translateY(-2em);/* move it up more */
}

input:focus,
input:valid {
  box-shadow: none;
  outline: none;
  background-position: 0 0;
}

<input placeholder="" id="User" type="text" required><label for="User">Username</label>
<input id="pwd" placeholder="" type="password" required><label for="pwd">Password</label>

其他CSS示例，其中标签在填充字段时位于顶部

label {
  position: absolute;
  margin-top: -1.75em;/*climbs under the input */
  transition: all 0.3s ease-in-out;
}
input {
  position: relative;
  z-index: 1;/* set input on top of label. opaque white bg color can be used to lighten label's color */
  width: 100%;
  display: block;
  border: none;
  padding: 20px 0 10px 0;
  border-bottom: solid 1px #343a40;
 transition: all 0.3s cubic-bezier(0.64, 0.09, 0.08, 1);
  transition: all 0.3s cubic-bezier(0.64, 0.09, 0.08, 1);
  background:linear-gradient(
    to top,
    rgba(255, 255, 255, 0) 99%,
    #007bff 1%
  );
  background: linear-gradient(to bottom, rgba(255, 255, 255, 0) 99%, #007bff 1%)
    rgba(255, 255, 255, 0.4);
  background-position: -1000px 0;
  background-size: auto 100%;
  background-repeat: no-repeat;
}
input:focus {
  color: #000;
}
input:valid + label,
input:focus + label, input:active + label {
  font-size: 12px;
  color: #007bff;
  font-size: 12px;
  transform: translateY(-2em);/* move it up more */
}

input:focus,
input:valid {
  box-shadow: none;
  outline: none;
  background-position: 0 0;
}

<input placeholder="" id="User" type="text" required><label for="User">Username</label>
<input id="pwd" placeholder="" type="password" required><label for="pwd">Password</label>

对于infos：:valid/:invalid是CSS选择器级别4，仍处于草稿状态https://drafts.csswg.org/selectors-4/#validity-pseudos但尚未完成http://caniuse.com/#search=%3Avalid

键入后保留占位符

1 个答案: