使JSpinner只读取数字，但也检测退格

问题描述

我正在尝试创建一个只接受数字的JSpinner，但我也想让它读取/响应退格。

I'm trying to make a JSpinner that will only accepts numbers but I also want it to read/respond to backspace.

public class test {
    JFrame frame;
    JPanel panel;
    JSpinner spinner;

    public test()
    {
        frame = new JFrame("test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setPreferredSize(new Dimension(200,200));

        panel = new JPanel();

        SpinnerNumberModel numSpin = new SpinnerNumberModel(10, 0,1000,1);
        spinner = new JSpinner(numSpin);
        JFormattedTextField txt = ((JSpinner.NumberEditor) spinner.getEditor()).getTextField();
        ((NumberFormatter) txt.getFormatter()).setAllowsInvalid(false);
        panel.add(spinner);

        frame.setContentPane(panel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);

    }
    public static void main(String[] args)

    {
        test test = new test();
    }
}

上面的代码仅用于制作数字，但这不是不允许我退格。我在这个网站上找到了一些例子，但它们都是用C语言编写的。

The code above works to make only numbers but this doesn't allow me to backspace. I found some examples on this site but they were written for C.

推荐答案

• 你是正确的 JFormattedTextField 没有正确实现到 JSpinner ，你有实现 DocumentFilter 用于过滤不需要的 Chars 从keyboad键入或从ClipBoard粘贴，（感谢@StanislavL）

  • you are right JFormattedTextField isn't correctly implemented to JSpinner, you have implements DocumentFilter for filtering of un_wanted Chars typed from keyboad or pasted from ClipBoard, (thanks to @StanislavL)

    您已自行解决 selectAll（）上的 focusGained（）包裹在<$ c $中c> invokeLater（），

    you have solve by yourself issues with selectAll() on focusGained() wrapped into invokeLater(),

    示例

    import java.awt.BorderLayout;
    import javax.swing.JButton;
    import javax.swing.JFrame;
    import javax.swing.JSpinner;
    import javax.swing.SpinnerNumberModel;
    import javax.swing.SwingUtilities;
    import javax.swing.text.*;
    
    public class TestDigitsOnlySpinner {
    
        public static void main(String... args) {
            SwingUtilities.invokeLater((Runnable) new Runnable() {
    
                @Override
                public void run() {
                    JFrame frame = new JFrame("enter digit");
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    JSpinner jspinner = makeDigitsOnlySpinnerUsingDocumentFilter();
                    frame.getContentPane().add(jspinner, BorderLayout.CENTER);
                    frame.getContentPane().add(new JButton("just another widget"), BorderLayout.SOUTH);
                    frame.pack();
                    frame.setVisible(true);
                }
    
                private JSpinner makeDigitsOnlySpinner_BasicAttempt() {
                    JSpinner spinner = new JSpinner(new SpinnerNumberModel());
                    return spinner;
                }
    
                private JSpinner makeDigitsOnlySpinnerUsingDocumentFilter() {
                    JSpinner spinner = new JSpinner(new SpinnerNumberModel(0, 0, 20, 1));
                    JSpinner.NumberEditor jsEditor = (JSpinner.NumberEditor) spinner.getEditor();
                    final Document jsDoc = jsEditor.getTextField().getDocument();
                    if (jsDoc instanceof PlainDocument) {
                        AbstractDocument doc = new PlainDocument() {
    
                            private static final long serialVersionUID = 1L;
    
                            @Override
                            public void setDocumentFilter(DocumentFilter filter) {
                                if (filter instanceof MyDocumentFilter) {
                                    super.setDocumentFilter(filter);
                                }
                            }
                        };
                        doc.setDocumentFilter(new MyDocumentFilter());
                        jsEditor.getTextField().setDocument(doc);
                    }
                    return spinner;
                }
            });
        }
    
        private static class MyDocumentFilter extends DocumentFilter {
    
            @Override
            public void insertString(FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException {
                if (stringContainsOnlyDigits(string)) {
                    super.insertString(fb, offset, string, attr);
                }
            }
    
            @Override
            public void remove(FilterBypass fb, int offset, int length) throws BadLocationException {
                super.remove(fb, offset, length);
            }
    
            @Override
            public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
                if (stringContainsOnlyDigits(text)) {
                    super.replace(fb, offset, length, text, attrs);
                }
            }
    
            private boolean stringContainsOnlyDigits(String text) {
                for (int i = 0; i < text.length(); i++) {
                    if (!Character.isDigit(text.charAt(i))) {
                        return false;
                    }
                }
                return true;
            }
        }
    
        private TestDigitsOnlySpinner() {
        }
    }
    

    这篇关于使JSpinner只读取数字，但也检测退格的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！