我扩展了DocumentFilter类以限制要输入到文本字段中指定数字的字符数。这里是我的SSCE:在Java文本框中使用鼠标选择粘贴/替换字符(具有指定的字符数限制)
主要类:
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Font;
import java.net.*;
import java.io.*;
import java.util.Date;
import java.util.StringTokenizer;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import javax.swing.text.PlainDocument;
public class Sandbox implements Runnable {
private JFrame frame;
private JTextField inputField;
private JButton searchButton;
private int MAX_CHAR_LIMIT = 1;
public Sandbox() {
inputField = new JTextField();
inputField.setColumns(10);
inputField.setFont(new Font(null, Font.BOLD, 20));
}
@Override
public void run() {
frame = new JFrame("SSCE");
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setPreferredSize(new Dimension(500, 300));
PlainDocument doc = (PlainDocument) inputField.getDocument();
doc.setDocumentFilter(new DocumentCharLimitFilter(MAX_CHAR_LIMIT));
frame.getContentPane().setLayout(new FlowLayout());
frame.getContentPane().add(inputField);
frame.pack();
frame.setVisible(true);
}
public static void main(String args[]) {
SwingUtilities.invokeLater(new Sandbox());
}
}
DocumentCharLimitFilter类
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
public class DocumentCharLimitFilter extends DocumentFilter {
private int MAX_CHAR_LIMIT;
public DocumentCharLimitFilter(int maxChars) {
this.MAX_CHAR_LIMIT = maxChars;
}
// You don't need insertString() when entering text in JTextField.
@Override
public void replace(FilterBypass fb, int offset, int length, String newText, AttributeSet aSet) throws BadLocationException {
int oldTextLength = fb.getDocument().getLength();
String oldText = fb.getDocument().getText(0, oldTextLength);
String combinedText = oldText + newText;
if (combinedText.length() <= MAX_CHAR_LIMIT) {
super.replace(fb, offset, length, newText, aSet);
// paste characters upto maximum allowed limit
} else if (oldTextLength < MAX_CHAR_LIMIT) {
int cutPosition = MAX_CHAR_LIMIT - oldTextLength;
String cutToFit = newText.substring(0, cutPosition);
super.replace(fb, offset, length, cutToFit, aSet);
} else {
System.out.println("Character limit of " + MAX_CHAR_LIMIT + " exceeded.");
}
}
}
当我火了上述程序,并尝试粘贴在现有的基础上增加一些新特性字符使用Ctrl + V,它将我带到DocumentCharLimitFilter的replace()方法的其他循环中,并且我得到:
超过1的字符限制。
从我所理解的所有这些,我使用鼠标和Ctrl + V粘贴的新角色被视为现有角色顶部的附加角色,并且我得到了上述消息。当我使用键盘输入字符时,它工作得很好。如果我将MAX_CHAR_LIMIT增加到2,我可以粘贴文本,但现在当我从键盘输入时,我可以输入两个我不想要的字符。
如何使上面的代码如同正常粘贴在现有文本之上并使用Ctr + V替换它,并仍将键盘字符限制到指定的限制?我是Java的初学者。如果我需要提供任何信息,我会很乐意这样做。谢谢。
更新:@camickr,@VGR非常感谢你! 我没有注意到replace()
方法中的length
参数。这是我在DocumentCharLimitFilter阶级都:
@Override
public void replace(FilterBypass fb, int offset, int length, String newText, AttributeSet aSet) throws BadLocationException {
System.out.println(fb.getClass());
int oldTextLength = fb.getDocument().getLength();
String oldText = fb.getDocument().getText(0, oldTextLength);
String combinedText = oldText + newText;
if (combinedText.length() <= MAX_CHAR_LIMIT) {
super.replace(fb, offset, length, newText, aSet);
// paste characters upto maximum allowed limit
} else if (oldTextLength < MAX_CHAR_LIMIT) {
int cutPosition = MAX_CHAR_LIMIT - oldTextLength;
String cutToFit = newText.substring(0, cutPosition);
super.replace(fb, offset, length, cutToFit, aSet);
// NEW CODE
// http://stackoverflow.com/questions/42512743/pasting-replacing-a-character-using-mouse-selection-in-java-textfield-with-spec
// length indicates number of characters highlighted using mouse or keyboard. This will work only when
// the entire text is highlighted (if entire text is not highlighted, it would get complicated)
// and when it is highlighted, I make sure that the new text to be pasted is within limits of the MAX_CHAR_LIMIT
} else if (length == MAX_CHAR_LIMIT) {
String correctedString = newText;
if (newText.length() > MAX_CHAR_LIMIT) {
correctedString = newText.substring(0, MAX_CHAR_LIMIT);
}
super.replace(fb, offset, length, correctedString, aSet);
} else {
System.out.println("Entered characters exceed specified limit of " + MAX_CHAR_LIMIT + "exceeded.");
}
}
尝试在[实现DocumentFilter](http://docs.oracle.com/javase/tutorial/uiswing/components/generaltext.html#filter)中找到的'DocumentFilter'来查看该过滤器是否有效。然后比较你的代码和工作代码,看看有什么不同。 – camickr
您忽略了传递给replace方法的'length'参数,该参数包含被替换的现有字符数。另外,我很好奇“在JTextField中输入文本时不需要insertString()”来自;我从来没有听说过。 – VGR
@VGR我认为这些字符不会被替换。新字符被附加到旧字符。我如何在这里使用长度参数?当我使用它时,inserString()永远不会被调用。它总是去替换()。 [检查此](http://stackoverflow.com/questions/6844848/documentfilter-insert-never-called) – retrazil