从JTextField只接受指定的模式,可以通过以下步骤实现:
下面是一个示例代码,演示如何限制JTextField只接受数字:
import javax.swing.*;
import javax.swing.text.*;
public class PatternTextFieldExample {
public static void main(String[] args) {
JFrame frame = new JFrame("PatternTextField Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JTextField textField = new JTextField(20);
((AbstractDocument) textField.getDocument()).setDocumentFilter(new PatternDocumentFilter("\\d+"));
frame.getContentPane().add(textField);
frame.pack();
frame.setVisible(true);
}
}
class PatternDocumentFilter extends DocumentFilter {
private String pattern;
public PatternDocumentFilter(String pattern) {
this.pattern = pattern;
}
@Override
public void insertString(FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException {
StringBuilder builder = new StringBuilder();
builder.append(fb.getDocument().getText(0, fb.getDocument().getLength()));
builder.insert(offset, text);
if (builder.toString().matches(pattern)) {
super.insertString(fb, offset, text, attr);
}
}
@Override
public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
StringBuilder builder = new StringBuilder();
builder.append(fb.getDocument().getText(0, fb.getDocument().getLength()));
builder.replace(offset, offset + length, text);
if (builder.toString().matches(pattern)) {
super.replace(fb, offset, length, text, attrs);
}
}
}
这个示例代码创建了一个带有限制的JTextField,只接受数字输入。PatternDocumentFilter类继承自DocumentFilter,并在insertString和replace方法中使用正则表达式来检查插入或替换的文本是否为数字。在主方法中,将PatternDocumentFilter对象应用到JTextField的Document中。
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