java强制JTextField只能是大写 [英] java force JTextField to be uppercase only

问题描述

是否有一种方法可以强制将 JTextField 中的所有用户输入在Java中变为大写?

Is there a way to force all user input in a JTextField to be uppercase in Java?

推荐答案

一个完整的工作示例可能会对您有所帮助

a complete working example may help you

import java.awt.Dimension;
import java.awt.FlowLayout;

import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;

public class UpperCasedTextFieldTester extends JFrame {
    /** */
    private static final long serialVersionUID = -4767854098431909437L;

    public UpperCasedTextFieldTester(){
        setSize(200, 200);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new FlowLayout(FlowLayout.LEFT));

        DocumentFilter filter = new UppercaseDocumentFilter();

        JTextField firstName = new JTextField();
        firstName.setPreferredSize(new Dimension(100, 20));
        ((AbstractDocument) firstName.getDocument()).setDocumentFilter(filter);

        JTextField lastName = new JTextField();
        lastName.setPreferredSize(new Dimension(100, 20));
        ((AbstractDocument) lastName.getDocument()).setDocumentFilter(filter);

        add(firstName);
        add(lastName);
    }

    public static void main(String[] args) {
        new UpperCasedTextFieldTester().setVisible(true);
    }

}

class UppercaseDocumentFilter extends DocumentFilter {
    public void insertString(DocumentFilter.FilterBypass fb, int offset,
            String text, AttributeSet attr) throws BadLocationException {

        fb.insertString(offset, text.toUpperCase(), attr);
    }

    public void replace(DocumentFilter.FilterBypass fb, int offset, int length,
            String text, AttributeSet attrs) throws BadLocationException {

        fb.replace(offset, length, text.toUpperCase(), attrs);
    }
}

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