Java如何将JTextField文本格式化为大写？
JTextField通过使用方法DocumentFilter向JTextField组件中添加a，可以轻松地将文本更改为大写setDocumentFilter()。该DocumentFilter让我们筛选器操作的文档中的更改，如插入，替换和删除。
下面的代码段向我们展示了如何实现。
package org.nhooo.example.swing;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.HeadlessException;
public class DocumentFilterExample extends JFrame {
public DocumentFilterExample() throws HeadlessException {
initComponents();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new DocumentFilterExample().setVisible(true));
}
protected void initComponents() {
setSize(250, 250);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
getContentPane().setLayout(new FlowLayout(FlowLayout.LEFT));
JTextField firstName = new JTextField();
firstName.setPreferredSize(new Dimension(150, 20));
JTextField lastName = new JTextField();
lastName.setPreferredSize(new Dimension(150, 20));
DocumentFilter filter = new UppercaseDocumentFilter();
AbstractDocument firstNameDoc = (AbstractDocument) firstName.getDocument();
firstNameDoc.setDocumentFilter(filter);
AbstractDocument lastNameDoc = (AbstractDocument) lastName.getDocument();
lastNameDoc.setDocumentFilter(filter);
getContentPane().add(new JLabel("First Name: "));
getContentPane().add(firstName);
getContentPane().add(new JLabel("Last Name: "));
getContentPane().add(lastName);
}
static class UppercaseDocumentFilter extends DocumentFilter {
@Override
public void insertString(DocumentFilter.FilterBypass fb, int offset, String text, AttributeSet attr)
throws BadLocationException {
fb.insertString(offset, text.toUpperCase(), attr);
}
@Override
public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attrs)
throws BadLocationException {
fb.replace(offset, length, text.toUpperCase(), attrs);
}
}
}