如何解决如何删除最后一行/组件/图标/小部件/等来自 JTextPane
我有一个庞大的 Java 项目，它使用像 UI 这样的控制台。对于控制台，我使用 JTextPane。最近我需要分别删除第一行和最后一行的方法。我删除第一行的方法很简单，如下
public void removeFirstLine() {
try {
Element root = outputArea.getDocument().getDefaultRootElement();
Element first = root.getElement(0);
outputArea.getDocument().remove(first.getStartOffset(),first.getEndOffset());
outputArea.setCaretPosition(outputArea.getDocument().getLength());
} catch (BadLocationException e) {
ErrorHandler.handle(e);
}
}
然而，当我尝试删除最后一行（不是文本，我重复不是文本）时，我的问题就出现了。该行可以是任何可附加到 JTextPane 的内容，例如自定义组件、文本字符串、图标等。如果有人知道如何删除附加到 JTextPane 的最后一个“东西”，我将永远感激您。
编辑：添加最小的可重现示例：
import javax.swing.*;
import javax.swing.text.*;
public class Test {
public static void main(String[] args) {
new test();
}
private static final String ELEM = AbstractDocument.ElementNameAttribute;
private static final String ICON = StyleConstants.IconElementName;
private static final String COMP = StyleConstants.ComponentElementName;
private JTextPane outputArea;
test() {
try {
//init pane
outputArea = new JTextPane();
//insert component
JTextField c = new JTextField(20);
Style cs = outputArea.getStyledDocument().addStyle("name",null);
StyleConstants.setComponent(cs,c);
outputArea.getStyledDocument().insertString(outputArea.getStyledDocument().getLength(),"string",cs);
//new line
println("");
//add string
println("this is a string added to the pane");
//add image
outputArea.insertIcon(new ImageIcon("/path/to/image.png"));
//new line
println("");
//before
printContents();
//----------------------------
//call removeLastLine() as many times as needed and it should remove the last added "thing"
//regardless of the order added (ex: component,text,icon should function the same as text,component obvIoUsly)
//changes should be reflected here
printContents();
} catch (Exception e) {
e.printstacktrace();
}
}
public void removeLastLine() {
//Todo remove last line of text,last component,last image icon,etc.
}
public void println(String Usage) {
try {
StyledDocument document = (StyledDocument) outputArea.getDocument();
document.insertString(document.getLength(),Usage + "\n",null);
outputArea.setCaretPosition(outputArea.getDocument().getLength());
}
catch (Exception e) {
e.printstacktrace();
}
}
public void printContents() {
try {
ElementIterator iterator = new ElementIterator(outputArea.getStyledDocument());
Element element;
while ((element = iterator.next()) != null) {
System.out.println(element);
AttributeSet as = element.getAttributes();
if (as.containsAttribute(ELEM,ICON)) {
System.out.println(StyleConstants.getIcon(as).getClass());
}
else if (as.containsAttribute(ELEM,COMP)) {
System.out.println(StyleConstants.getComponent(as).getClass());
}
}
} catch (Exception e) {
e.printstacktrace();
}
}
}
解决方法
以下是我之前使用过的用于删除文本的代码：
public void removeLastLine() {
// We use start minus 1 to make sure we remove the newline
// character of the previous line
Element root = outputArea.getDocument().getDefaultRootElement();
Element line = root.getElement(root.getElementCount() - 1);
int start = line.getStartOffset();
int end = line.getEndOffset();
try
{
outputArea.getDocument().remove(start - 1,end - start);
}
catch(BadLocationException ble)
{
System.out.println(ble);
}
}
似乎也适用于其他对象，因为“after”输出与“before”输出不同。
我会让您验证文本窗格是否按预期更新。
获取了代码编辑：
尝试删除第一行时，上面的代码不起作用，因为起始偏移量将为负。
以下是也处理删除第一行的更新版本：
import java.awt.*;
import javax.swing.*;
import javax.swing.*;
import javax.swing.text.*;
public class Test {
public static void main(String[] args) {
new Test();
}
private static final String ELEM = AbstractDocument.ElementNameAttribute;
private static final String ICON = StyleConstants.IconElementName;
private static final String COMP = StyleConstants.ComponentElementName;
private JTextPane outputArea;
Test() {
try {
//init pane
outputArea = new JTextPane();
JButton button = new JButton("Remove Last Line");
button.addActionListener((e) -> removeLastLine());
JFrame frame = new JFrame();
frame.add( new JScrollPane(outputArea) );
frame.add( button,BorderLayout.PAGE_END);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setSize(300,300);
frame.setLocationByPlatform( true );
frame.setVisible( true );
println("first line");
//insert component
JTextField c = new JTextField(20);
Style cs = outputArea.getStyledDocument().addStyle("name",null);
StyleConstants.setComponent(cs,c);
outputArea.getStyledDocument().insertString(outputArea.getStyledDocument().getLength(),"string",cs);
//new line
println("");
//add string
println("this is a string added to the pane");
//add image
outputArea.insertIcon(new ImageIcon("about16.gif"));
//new line
println("\nsecond last line");
} catch (Exception e) {
e.printStackTrace();
}
}
public void removeLastLine()
{
// We use start minus 1 to make sure we remove the newline
// character of the previous line
Element root = outputArea.getDocument().getDefaultRootElement();
Element line = root.getElement(root.getElementCount() - 1);
int start = line.getStartOffset();
int end = line.getEndOffset();
try
{
int offset = start - 1;
int length = end - start;
// removing the first line
if (offset < 0)
{
offset = 0;
length -= 1;
}
outputArea.getDocument().remove(offset,length);
}
catch(BadLocationException ble)
{
System.out.println(ble);
}
}
public void println(String Usage) {
try {
StyledDocument document = (StyledDocument) outputArea.getDocument();
document.insertString(document.getLength(),Usage + "\n",null);
outputArea.setCaretPosition(outputArea.getDocument().getLength());
}
catch (Exception e) {
e.printStackTrace();
}
}
}
我用我整个下午写的以下代码解决了这个问题。
/**
* Removes the last "thing" addeed to the JTextPane whether it's a component,* icon,or string of multi-llined text.
*
* In more detail,this method figures out what it'll be removing and then determines how many calls
* are needed to {@link StringUtil#removeLastLine()}
*/
public void removeLast() {
boolean removeTwoLines = false;
LinkedList<Element> elements = new LinkedList<>();
ElementIterator iterator = new ElementIterator(outputArea.getStyledDocument());
Element element;
while ((element = iterator.next()) != null) {
elements.add(element);
}
int leafs = 0;
for (Element value : elements)
if (value.getElementCount() == 0)
leafs++;
int passedLeafs = 0;
for (Element value : elements) {
if (value.getElementCount() == 0) {
if (passedLeafs + 3 != leafs) {
passedLeafs++;
continue;
}
if (value.toString().toLowerCase().contains("icon") || value.toString().toLowerCase().contains("component")) {
removeTwoLines = true;
}
}
}
if (removeTwoLines) {
removeLastLine();
}
removeLastLine();
}
/**
* Removes the last line added to the linked JTextPane. This could appear to remove nothing,* but really be removing just a newline (line break) character.
*/
public void removeLastLine() {
try {
LinkedList<Element> elements = new LinkedList<>();
ElementIterator iterator = new ElementIterator(outputArea.getStyledDocument());
Element element;
while ((element = iterator.next()) != null) {
elements.add(element);
}
int leafs = 0;
for (Element value : elements)
if (value.getElementCount() == 0)
leafs++;
int passedLeafs = 0;
for (Element value : elements) {
if (value.getElementCount() == 0) {
if (passedLeafs + 2 != leafs) {
passedLeafs++;
continue;
}
outputArea.getStyledDocument().remove(value.getStartOffset(),value.getEndOffset() - value.getStartOffset());
}
}
} catch (BadLocationException ignored) {}
catch (Exception e) {
e.printStackTrace();
}
}
可以在以下位置查看完整代码：https://github.com/NathanCheshire/Cyder/blob/master/src/cyder/utilities/StringUtil.java
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