MDL 浮动标签文本字段：强制标签浮动

Question

这个 HTML 文件应该在单击“添加文本”按钮时将“新文本”写入文本字段。有谁知道如何使文本字段的标签在单击按钮时浮动，而不是这样做？

谢谢。

textbox.html

<!--Template page for all other pages-->
<!--Based MDL items -->
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Textfield Demo</title>
  <!-- Import MDL libraries -->
  <link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons">
  <link rel="stylesheet" href="https://code.getmdl.io/1.3.0/material.blue-red.min.css"/>
  <script defer src="https://code.getmdl.io/1.3.0/material.min.js"></script>
  <script src="js/config.js"></script>
</head>
<body>
  <div class="mdl-layout mdl-js-layout mdl-layout--fixed-header">
    <main class="mdl-layout__content">
      <div class="page-content">
        <div class="mdl-grid">
          <div class="mdl-cell mdl-cell--1-col"></div>
          <div class="mdl-cell--10-col" style="text-align:center; height:60vh">
            <div class="mdl-textfield mdl-js-textfield mdl-textfield--floating-label">
              <input class="mdl-textfield__input" type="text" id="search-bar">
              <label class="mdl-textfield__label" for="search-bar">Text...</label>
            </div>
            <button class="mdl-button mdl-js-button mdl-button--raised mdl-js-ripple-effect mdl-button--accent" 
            id="button" onclick="addText()">Add Text</button><br>
          </div>
          <div class="mdl-cell mdl-cell--1-col"></div>
        </div>
      </div>
    </main>
  </div>
  <script src="textbox.js"></script>
</body>
</html>

textbox.js

function addText() {
    let searchBar = document.getElementById('search-bar');
    let text = 'New text';
    searchBar.value = text;
}

Answer 1

您需要先“关注”(reference) 输入才能获得来自 Material Design 的正确动画，因为它应该具有 is-dirty class 你还需要将它添加到父级。

 function addText() {
    let searchBar = document.getElementById('search-bar');
    // These two lines:
    searchBar.focus();
    searchBar.parentElement.classList.add("is-dirty");

    let text = 'New text';
    searchBar.value = text;
}

MDL 浮动标签文本字段：强制标签浮动

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