java - Java中使用DocumentFilter扫描条码

Question

我的条形码包括“1039723170303CC15-78” 我使用 DocumentFilter 的原因是我想将数字限制为仅 7 位。 其余数字自动转到第二个文本字段。

我的代码仅工作集 7 位数字，并非所有其余数字都会进入下一个文本字段。 (即，"1039723" 转到第一个文本字段，"70303CC15-78" 转到第二个文本字段。第二个文本字段中缺少 "1"。

我该如何解决这个问题？

lblTest = new JLabel("Testing : ");
panel.add(lblText, "cell 0 1,alignx trailing");

txtTest = new JTextField(7);

 AbstractDocument d = (AbstractDocument) txtTest.getDocument();
 d.setDocumentFilter(new DocumentFilter() {
     @Override  
        public void insertString(DocumentFilter.FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException  
        {
            if(fb.getDocument().getLength()+string.length()>7)
            {                       
                return;                     
            }
            fb.insertString(offset, string, attr);                  
        }  


        @Override  
        public void remove(DocumentFilter.FilterBypass fb, int offset, int length) throws BadLocationException 
        {                   
            fb.remove(offset, length);
        }


        @Override  
        public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attrs)throws BadLocationException 
        {  
                 if(fb.getDocument().getLength()+text.length()>7)
                 {
                     txtTest.transferFocus();
                    System.out.println("print.." +txtTest.getText());
                    return;
                }
                fb.insertString(offset, text, attrs);
        }
 });

打印输出:

print Mo No.:1039723
print Mo No.:1039723
print Mo No.:1039723

Answer 1

您遇到的基本问题是您正在检查的文本已被丢弃并且从未应用于任何内容。

例如，如果输入的文本是(假设一次一个字符)123456789，则 8 将被忽略，因为 9 将被发送到另一个字段。

您需要做的是手动设置下一个字段的文本以及您要忽略的文本。

现在，您的电流有两个根本缺陷。

1. 它没有考虑到 replace 应删除任何选定字符的事实
2. 不考虑将文本附加到字段时会发生什么
3. 不考虑文本是否在字段末尾以外的偏移处插入

这个例子试图回答所有这些问题

import javax.swing.JFrame;
import javax.swing.JPanel;
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 Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame("Test");
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            JTextField field1 = new JTextField(7);
            JTextField field2 = new JTextField(7);
            ((AbstractDocument) field1.getDocument()).setDocumentFilter(new LimitDocumentFilter(field2));
            add(field1);
            add(field2);
        }

    }

    public class LimitDocumentFilter extends DocumentFilter {

        private JTextField next;

        public LimitDocumentFilter(JTextField next) {
            this.next = next;
        }

        @Override
        public void insertString(FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException {
            super.insertString(fb, offset, text, attr);
            String textValue = fb.getDocument().getText(0, fb.getDocument().getLength());
            if (textValue.length() > 7) {
                remove(fb, 7, fb.getDocument().getLength() - 7);
                String overflow = textValue.substring(7);
                next.requestFocusInWindow();
                SwingUtilities.invokeLater(new Runnable() {
                    @Override
                    public void run() {
                        next.setText(overflow);
                        next.setCaretPosition(overflow.length());
                    }
                });
            }
        }

        @Override
        public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
            fb.remove(offset, length);
            insertString(fb, offset, text, attrs);
        }
    }

}

这真正需要的是一个委托(delegate)模型，它不是通过 DocumentFilter 改变字段焦点，而是将该责任委托(delegate)给其他观察者，并将溢出文本传递给它

更新

好的，这是一个更新版本，它提供了三种设置文本的方式:

1. 直接通过setText
2. 从剪贴板粘贴
3. 通过Robot注入(inject)键盘缓冲区的击键

这提供了条形码扫描仪“可能”如何工作的最佳示例

import java.awt.AWTException;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.StringSelection;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusListener;
import java.awt.event.KeyEvent;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.UIDefaults;
import javax.swing.UIManager;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
import javax.swing.text.DocumentFilter.FilterBypass;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame("Test");
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            JTextField field1 = new JTextField(7);
            JTextField field2 = new JTextField(7);
            LimitDocumentFilter filter = new LimitDocumentFilter();
            filter.add(new LimitListener() {
                @Override
                public void limitReached(LimitDocumentFilter filter, String overflow) {
                    // This is to overcome the issue of MacOS autoselecting the
                    // text when it gets focus ... dumb
                    FocusListener[] listeners = field2.getFocusListeners();
                    for (FocusListener listener : listeners) {
                        field2.removeFocusListener(listener);
                    }
                    field2.setText(overflow);
                    field2.requestFocusInWindow();
                    field2.setCaretPosition(overflow.length());
                    SwingUtilities.invokeLater(new Runnable() {
                        @Override
                        public void run() {
                            for (FocusListener listener : listeners) {
                                field2.addFocusListener(listener);
                            }
                        }
                    });
                }
            });
            ((AbstractDocument) field1.getDocument()).setDocumentFilter(filter);
            add(field1);
            add(field2);

            JButton sim = new JButton("Simulate");
            sim.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    field1.setText(null);
                    field2.setText(null);
                    field1.requestFocusInWindow();
                    SwingUtilities.invokeLater(new Runnable() {
                        @Override
                        public void run() {
                            Thread t = new Thread(new Simulator());
                            t.start();
                        }
                    });
                }
            });
            JButton paste = new JButton("Paste");
            paste.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    field1.setText(null);
                    field2.setText(null);
                    String text = "1234567abcdefg";
                    Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
                    clipboard.setContents(new StringSelection(text), null);
                    field1.requestFocusInWindow();
                    SwingUtilities.invokeLater(new Runnable() {
                        @Override
                        public void run() {
                            field1.paste();
                        }
                    });
                }
            });
            JButton set = new JButton("Set");
            set.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    field1.setText(null);
                    field2.setText(null);
                    field1.setText("1234567abcdefghijklmnopqrstuvwxyz");
                }
            });

            add(sim);
            add(paste);
            add(set);
        }

    }

    public class Simulator implements Runnable {

        @Override
        public void run() {
            try {
                Robot bot = new Robot();
                type(KeyEvent.VK_1, bot);
                type(KeyEvent.VK_2, bot);
                type(KeyEvent.VK_3, bot);
                type(KeyEvent.VK_4, bot);
                type(KeyEvent.VK_5, bot);
                type(KeyEvent.VK_6, bot);
                type(KeyEvent.VK_7, bot);

                type(KeyEvent.VK_A, bot);
                type(KeyEvent.VK_B, bot);
                type(KeyEvent.VK_C, bot);
                type(KeyEvent.VK_D, bot);
                type(KeyEvent.VK_E, bot);
                type(KeyEvent.VK_F, bot);
                type(KeyEvent.VK_G, bot);
            } catch (AWTException ex) {
                ex.printStackTrace();
            }
        }

        protected void type(int keyStoke, Robot bot) {
            bot.keyPress(keyStoke);
            bot.keyRelease(keyStoke);
        }

    }

    public interface LimitListener {

        public void limitReached(LimitDocumentFilter filter, String overflow);
    }

    public class LimitDocumentFilter extends DocumentFilter {

        private List<LimitListener> listeners = new ArrayList<>(25);

        public LimitDocumentFilter() {
        }

        public void add(LimitListener listener) {
            listeners.add(listener);
        }

        public void remove(LimitListener listener) {
            listeners.remove(listener);
        }

        protected void limitReached(String overflow) {
            for (LimitListener listener : listeners) {
                listener.limitReached(this, overflow);
            }
        }

        @Override
        public void insertString(FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException {
            super.insertString(fb, offset, text, attr);
            String textValue = fb.getDocument().getText(0, fb.getDocument().getLength());
            if (textValue.length() > 7) {
                remove(fb, 7, fb.getDocument().getLength() - 7);
                String overflow = textValue.substring(7);
                limitReached(overflow);
            }
        }

        @Override
        public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
            fb.remove(offset, length);
            insertString(fb, offset, text, attrs);
        }
    }

}