负整数和正整数的DocumentFilter

Question

我知道这是一个常见的问题，但我正在尝试创建一个只接受int数的TextField，它几乎完成了，下面是代码：

创建textfield：

nome = new JFormattedTextField();
            nome.setHorizontalAlignment(SwingConstants.CENTER);
            nome.setColumns(2);

            DocumentFilter filtro = new FiltroNumero();
            ((AbstractDocument) nome.getDocument()).setDocumentFilter(filtro);

            panel.add(nome);

DocummentFilter：

public class FiltroNumero extends DocumentFilter{

    public void insertString(DocumentFilter.FilterBypass fb, int offset, int length,
              String text, javax.swing.text.AttributeSet attr)

              throws BadLocationException {
                    fb.insertString(offset, text.replaceAll("[^-0-9]", ""), attr);
         }  
}

这样，TextField将只接受数字和"-"，但这意味着"1-“是一个可能的值。

我需要的是一种使textfield在第一个字符之后不接受减号的方法。

如果有人能帮我，我会很高兴的

Answer 1

您只需从Document中获取整个文本(即“前替换”)，然后从该文档文本中创建一个新的字符串，添加text参数。然后，只需检查与整数(负或正)匹配的完整正则表达式。如果匹配，则执行替换操作。类似于：

@Override
public void replace(FilterBypass fb, int offs, int length,
        String str, AttributeSet a) throws BadLocationException {

    String text = fb.getDocument().getText(0,
            fb.getDocument().getLength());

    StringBuilder builder = new StringBuilder(text);
    builder.insert(offs, str);
    String newText = builder.toString();

    // check
    System.out.println("text = " + text 
                   + ", offset = " + offs 
                   + ", newText = " + newText);

    if (newText.matches("(-)?\\d*")) {
        super.replace(fb, offs, length, str, a);
    } else {
        Toolkit.getDefaultToolkit().beep();
    }
}

注意:您应该使用的是replace而不是insertString，尽管覆盖两者都没有坏处。

这是一个完整的演示

import java.awt.Toolkit;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;

public class FilterDemo {

    public FilterDemo() {
        JFrame frame = new JFrame();
        frame.add(createFilteredField());
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationByPlatform(true);
        frame.setVisible(true);

    }

    private  JTextField createFilteredField() {
        JTextField field = new JTextField(10);
        AbstractDocument document = (AbstractDocument) field.getDocument();
        document.setDocumentFilter(new DocumentFilter() {

            @Override
            public void replace(FilterBypass fb, int offs, int length,
                    String str, AttributeSet a) throws BadLocationException {

                String text = fb.getDocument().getText(0,
                        fb.getDocument().getLength());

                StringBuilder builder = new StringBuilder(text);
                builder.insert(offs, str);
                String newText = builder.toString();

                // check
                System.out.println("text = " + text 
                               + ", offset = " + offs 
                               + ", newText = " + newText);

                if (newText.matches("(-)?\\d*")) {
                    super.replace(fb, offs, length, str, a);
                } else {
                    Toolkit.getDefaultToolkit().beep();
                }
            }


            @Override
            public void insertString(FilterBypass fb, int offs, String str,
                    AttributeSet a) throws BadLocationException {

                String text = fb.getDocument().getText(0,
                        fb.getDocument().getLength());

                StringBuilder builder = new StringBuilder(text);
                builder.insert(offs, str);
                String newText = builder.toString();

                // checks
                System.out.println("text = " + text 
                               + ", offset = " + offs 
                               + ", newText = " + newText);

                if (newText.matches("(-)?\\d*")) {
                    super.insertString(fb, offs, str, a);
                } else {
                    Toolkit.getDefaultToolkit().beep();
                }
            } 
        });
        return field;
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new FilterDemo();
            }
        });
    }
}