对于那些需要更具体地解释 HTMLEditorKit 处理列表的特殊方式的人来说，这一切都归结为生成的标记。我会尽量让它保持简单。让我们回过头来谈谈 Swing 中的 HTML 文档。
事实证明，Swing 依靠段落来进行光标定位和导航。例如，每次你写一个新行，就会生成一个新的页面。甚至文档的相应视图也取决于正确位置是否存在段落。文档中必须始终有一个段落。否则，奇怪的事情就会开始发生。
那么，如果文档完全空白会发生什么？当然，那里不需要一个段落。好吧，令人难以置信的是，即使在那种情况下也有一段。这是文档所称的p-implicit或implicit paragraph的效果之一。为空白文档生成的 HTML 是：
<html>
<head></head>
<body>
<p style="margin-top: 0">
</p>
</body>
</html>
预计，当您插入一个列表时，它被放置在段落内：
<html>
<head></head>
<body>
<p style="margin-top: 0">
<ul>
<li>
</li>
</ul>
</p>
</body>
</html>
...这当然是无效的标记（不仅仅是因为头部没有标题）。可是等等！它变得更加有趣。插入列表后，文档的“内部指针”就在结束</ul>标记之后。因此，如果您键入“Hello”，它将被放置在列表之外：
<html>
<head></head>
<body>
<p style="margin-top: 0">
<ul>
<li>
</li>
</ul>
Hello
</p>
</body>
</html>
这就是为什么“Hello”相对于插入的项目符号出现在右侧的原因。现在，正如斯蒂芬在问题中提到的那样，setText(getText())神奇地解决了这个问题。这是因为手动设置 JTextPane 实例的内容会触发解析器，进而将“内部指针”放置在应有的位置；列表内。现在，当您键入“Hello”时，它会显得更接近项目符号。我说得更近了，因为 HTML 仍有一些不正确的地方：
<html>
<head></head>
<body>
<p style="margin-top: 0">
<ul>
<li>
Hello
</li>
</ul>
</p>
</body>
</html>
请注意，列表中没有包含新文本的段落。这就是为什么文本不会出现在项目符号旁边的原因。
你如何处理这一切？嗯，这就是斯蒂芬所说的棘手的一点。正如我们所见，您将面临错误（例如这个）、未记录的故障（例如这个）和默认行为的组合。最简单的方法是使用 Stephane 列表中的一种解决方案。我同意Shef是最好的，但自 2009 年以来没有那么多活动（！）。就个人而言，我发现Stanislav 的网站对所有 EditorKit 都非常有用。
你也可以看看ADAPRO：一个非常稳定的开源辅助编辑器，我曾大量参与其中。辅助功能有问题，但核心编辑功能已经过全面测试。以下代码来自该项目。它需要SHEF 的net.atlanticbb.tantlinger.ui.text包中的ElementWriter类。
//HTML representation of an empty paragraph
private static final String sEmptyParagraph = "<p style=\"margin-top: 0\"></p>";
/**
* Translates into HTML a given element of the document model.
* @param element Element to serialise to a HTML string
* @param out Serialiser to HTML string
* @return HTML string "equivalent" to given element
*/
static String extractHTML (Element element, StringWriter out) {
ElementWriter writer = new ElementWriter (out, element);
try {
writer.write();
} catch (IOException e) {
System.out.println ("Error encountered when serialising element: " +e);
e.printStackTrace();
} catch (BadLocationException e) {
System.out.println ("Error encountered when extracting HTML at the element's position: " +e);
e.printStackTrace();
}
return out.toString();
}
/**
* Determines if the parent element of the current paragraph element is one of a number provided as a list
* of tag names. If so, it returns the parent element.
* @param document Document model of the text
* @param iCaretPos Caret's current position
* @param sTags Possible parent tags
* @return Parent element
*/
static Element getNearestParent (HTMLDocument document, int iCaretPos, String sTags) {
Element root;
root = document.getParagraphElement (iCaretPos);
do {
root = root.getParentElement();
} while (sTags.indexOf (root.getName()) == -1);
return root;
}
/**
* Inserts all HTML tags required to build an ordered/unordered list at the caret's current position.
* If the aim is instead to turn the numbered/bulleted paragraphs into plain ones, it takes care of
* deleting the necessary tags.
* @param sTypeList Type of list to build: "ul" or "ol".
* @param textArea Editable area containing text.
*/
static void insertList (String sTypeList, JTextPane textArea) {
boolean bOnlyListSelected; //selection includes a list exclusively
int iStartIndex, iEndIndex, //element indexes included in selection
iStartSel, iEndSel, //starting and ending offset of selected text
iItemNo, //total number of list items
i;
String sHTML, //HTML code of text represented by a given element
sHTMLBlock, //HTML code block to be inserted into document model
sRest; //part of the text remaining unselected after the selected block
HTML.Tag tag; //current list tag
HTMLDocument document; //data model underlying the typed text
Element root, //root element of the document model tree
section; //element representing a block of text
SimpleAttributeSet attribIns; //backup of current input attributes
//Fetches the current document
document = (HTMLDocument) textArea.getDocument();
//Finds the topmost parent element of the current paragraph (effectively, is the list inside a table?)
root = getNearestParent (document, textArea.getCaretPosition(), "td body");
//Range of elements included in the selection
iStartSel = textArea.getSelectionStart();
iEndSel = textArea.getSelectionEnd();
iStartIndex = root.getElementIndex (iStartSel);
iEndIndex = root.getElementIndex (iEndSel);
//HTML-related initialisations
sHTML = "";
sHTMLBlock = "";
tag = null;
//Checks if selection is comprised of just list items
i = iStartIndex;
bOnlyListSelected = true;
do {
tag = HTML.getTag (root.getElement(i).getName());
//Is it a list tag?
if ((tag == null) || ((!tag.equals (HTML.Tag.OL)) && (!tag.equals (HTML.Tag.UL))))
bOnlyListSelected = false;
i++;
} while (bOnlyListSelected && (i <= iEndIndex));
//Back up current input attributes
attribIns = new SimpleAttributeSet (textArea.getInputAttributes());
try {
//At some point in the selection there is no previous list...
if (!bOnlyListSelected) {
//Inserts <LI> tags for every text block
for (i = iStartIndex; i <= iEndIndex; i++) {
section = root.getElement(i);
tag = HTML.getTag (section.getName());
//Retrieves current HTML
sHTML = extractHTML (section, new StringWriter());
//If it is non-listed text, reconstitute the paragraph
if (tag == null)
sHTML = "<p style=\"margin-top: 0;\">" +sHTML+ "</p>";
//Text in a list already => no nesting (delete <UL>/<OL> tags)
if (sHTML.indexOf("<li>") != -1) {
sHTML = sHTML.substring (sHTML.indexOf("<li>"), sHTML.length());
sHTML = sHTML.substring (0, sHTML.lastIndexOf("</li>") + 5);
//Non-listed text => add <LI> tags
} else sHTML = "<li>" +sHTML+ "</li>";
sHTMLBlock = sHTMLBlock + sHTML;
}
sHTMLBlock = "<"+sTypeList+">" +sHTMLBlock.trim()+ "</"+sTypeList+">";
//Gets the text coming after caret or end of selection
sRest = textArea.getText (iEndSel, document.getLength() - iEndSel);
//Adds an empty paragraph at the end of the list if the latter coincides with the end of the document
//or if the rest of the document is empty. This is to avoid a glitch in the editor kit's write() method.
//http://java-sl.com/tip_html_kit_last_empty_par.html
if ((root.getElement(iEndIndex).getEndOffset() == root.getEndOffset()) ||
sRest.replaceAll ("[\\p{Z}\\s]", "").trim().isEmpty())
sHTMLBlock = sHTMLBlock + sEmptyParagraph;
//Removes the remaining old non-listed text block and saves resulting HTML string to document model
document.setOuterHTML (root.getElement(iEndIndex), sHTMLBlock);
if (iEndIndex > iStartIndex)
document.remove (root.getElement(iStartIndex).getStartOffset(),
root.getElement(iEndIndex - 1).getEndOffset() -
root.getElement(iStartIndex).getStartOffset());
//Selection just includes list items
} else {
//Works out the list's length in terms of element indexes
root = root.getElement (root.getElementIndex (iStartSel));
iItemNo = root.getElementCount();
iStartIndex = root.getElementIndex (textArea.getSelectionStart());
iEndIndex = root.getElementIndex (textArea.getSelectionEnd());
//For everery <LI> block, remove the <LI> tag
for (i = iStartIndex; i <= iEndIndex; i++) {
sHTML = extractHTML (root.getElement(i), new StringWriter());
sHTML = sHTML.substring(sHTML.indexOf("<li>") + 4, sHTML.length());
sHTML = sHTML.substring(0, sHTML.lastIndexOf("</li>"));
sHTMLBlock = sHTMLBlock + sHTML;
}
//List selected partially? => divide list
if (iItemNo > (iEndIndex - iStartIndex + 1)) {
//Saves HTML string to document model
((HTMLEditorKit) textArea.getEditorKit()).insertHTML (document, root.getElement(iEndIndex).getEndOffset(),
sHTMLBlock, 3, 0, HTML.Tag.P);
//Removes the old block
document.remove (root.getElement(iStartIndex).getStartOffset(),
root.getElement(iEndIndex).getEndOffset() -
root.getElement(iStartIndex).getStartOffset());
//Removes the list tag associated with the block
} else document.setOuterHTML (root, sHTMLBlock.trim());
}
} catch (Exception eTexto) {
System.out.println ("Problemas al eliminar/insertar texto: " +eTexto);
eTexto.printStackTrace();
}
//Recover selection. Previous operations displace the cursor and thus selection highlight is lost
textArea.setSelectionStart (iStartSel);
textArea.setSelectionEnd (iEndSel);
//If only one list item has been created and is the first one, copy all previous style information to the list
if ((!bOnlyListSelected) && (iStartSel == iEndSel)) {
textArea.setCharacterAttributes (attribIns, false);
}
}
