像超级市场一样的Java长单打印

Question

我正在使用 Java SE 开发POS系统。我需要像超市账单一样打印长账单。

我希望使用 EPSON TM-U220D （https://www.epson.eu/products/sd/pos-printer/epson-tm-u220b-series）作为收据打印机。

但是问题是收据打印一段时间后会停止。。我使用了 java.awt.print.PrinterJob 来生成收据和打印。我从互联网上找到了代码。但是它没有按预期打印收据。

这是我在程序中使用的代码：

BillPrinter {

private DBQuery dbq;

    private String billid;

private Bill bill;

private BillItem billitems[];

private int maxTextLength = 34;
private int y = 0;
private int yShift = 10;

public BillPrinter(DBQuery dbq) {
    this.dbq = dbq;
}

public void printBill(String billid) {
    this.billid = billid;
    try {
        bill = dbq.getBillByBillID(billid);
        if (bill != null) {
            billitems = dbq.getBillItemByBill(bill);
            System.out.println(bill.getBillid() + " - " + bill.getId());
            if (billitems.length > 0) {


                PrinterJob printerJob = PrinterJob.getPrinterJob();

                PageFormat pageFormat = printerJob.defaultPage();

                Paper paper = new Paper();

                paper = new Paper();

                double **middleHeight** = billitems.length * 0.1;
                double **headerHeight** = 0.5;                
                double **footerHeight** = 0.5;                  

                double **width** = convert_CM_To_PPI(7);
                double **height** = convert_CM_To_PPI(headerHeight + middleHeight + footerHeight);
                paper.setSize(width, height);

                pageFormat.setPaper(paper);

                pageFormat.setOrientation(PageFormat.PORTRAIT);

                paper.setImageableArea(
                        convert_CM_To_PPI(0.025),
                        convert_CM_To_PPI(0.05),
                        width - convert_CM_To_PPI(0.035),
                        height - convert_CM_To_PPI(0.1)
                );

                printerJob.setPrintable(new BillPrintable(), pageFormat);

                try {
                    printerJob.print();
                } catch (PrinterException ex) {
                    ex.printStackTrace();
                }
            }
        }
    } catch (NullPointerException npe) {
        npe.printStackTrace();
    }

}

 private double convert_CM_To_PPI(double cm) {
    return toPPI(cm * 0.393600787);
}

private double toPPI(double inch) {
    return inch * 72d;
}

public class BillPrintable implements Printable {

    public int print(Graphics graphics, PageFormat pageFormat, int pageIndex)
            throws PrinterException {
        int result = NO_SUCH_PAGE;
        if (pageIndex == 0) {

            y = 10;

            Graphics2D g2d = (Graphics2D) graphics;

            g2d.translate((double) pageFormat.getImageableX(), (double)pageFormat.getImageableY());

            try {

                g2d.setFont(new Font("Monospaced", Font.BOLD, 10));
                TextLengthFormater(g2d, "----------------------------------");

                g2d.setFont(new Font("Monospaced", Font.BOLD, 10));
                TextLengthFormater(g2d, "<Company Name>");

                g2d.setFont(new Font("Monospaced", Font.PLAIN, 10));
                TextLengthFormater(g2d, "<Address>");
                TextLengthFormater(g2d, "<Contact>");
                TextLengthFormater(g2d, "<Email>");
                TextLengthFormater(g2d, "<Website>");

                g2d.setFont(new Font("Monospaced", Font.BOLD, 10));
                TextLengthFormater(g2d, "----------------------------------");

                g2d.setFont(new Font("Monospaced", Font.PLAIN, 8));
                TextLengthFormater(g2d, "Bill ID: " + billid);
                TextLengthFormater(g2d, "Date: " + bill.getDate());
                TextLengthFormater(g2d, "Description: " + bill.getDescription());

                g2d.setFont(new Font("Monospaced", Font.BOLD, 10));
                TextLengthFormater(g2d, "----------------------------------");

                g2d.setFont(new Font("Monospaced", Font.PLAIN, 8));
                for (int i = 0; i < billitems.length; i++) {
                    TextLengthFormater(g2d, billitems[i].getItem().getName());

                    StringBuilder sb = new StringBuilder("");
                    sb = addStringTo(sb, Integer.toString(billitems[i].getQuntity()), 3);
                    sb = addStringTo(sb, "X", 5);
                    sb = addStringTo(sb, Double.toString(billitems[i].getItem().getPrice()), 10);
                    sb = addStringTo(sb, "=", 5);
                    double amount = (billitems[i].getItem().getPrice() * billitems[i].getQuntity());
                    sb = addStringTo(sb, Double.toString(amount), 10);
                    TextLengthFormater(g2d, sb.toString());
                }

                g2d.setFont(new Font("Monospaced", Font.BOLD, 10));
                TextLengthFormater(g2d, "----------------------------------");

                g2d.setFont(new Font("Monospaced", Font.PLAIN, 8));
                double total = bill.getTotal() * 100 /(100 - billitems[0].getDiscount());
                TextLengthFormater(g2d, "Total: " + addStringTo(new StringBuilder(), Double.toString(total), 26).toString());
                TextLengthFormater(g2d, "Discount: " + addStringTo(new StringBuilder(), Double.toString(total - bill.getTotal()), 23).toString());
                TextLengthFormater(g2d, "Sub Total: " + addStringTo(new StringBuilder(), Double.toString((bill.getTotal())), 22).toString());

                TextLengthFormater(g2d, "Pay: " + addStringTo(new StringBuilder(), Double.toString(bill.getPayment()), 28).toString());
                TextLengthFormater(g2d, "Change: " + addStringTo(new StringBuilder(), Double.toString(bill.getPayment() - (bill.getTotal())), 25).toString());

                g2d.setFont(new Font("Monospaced", Font.BOLD, 10));
                TextLengthFormater(g2d, "----------------------------------");
                TextLengthFormater(g2d, "             THANK YOU");
                TextLengthFormater(g2d, "----------------------------------");
            } catch (Exception r) {
                r.printStackTrace();
            }
            result = PAGE_EXISTS;
        }
        return result;
    }
}

private void TextLengthFormater(Graphics2D g2d, String text) {
    Vector<String> vtr = new Vector<String>();
    while (text.length() > 0) {
        vtr.add(text.substring(0, (text.length() > maxTextLength ? maxTextLength : text.length())));
        text = text.substring((text.length() > maxTextLength ? maxTextLength : text.length()));
    }
    for (String str : vtr) {
        g2d.drawString(str, 0, y);
        y += yShift;
    }
}

private StringBuilder addStringTo(StringBuilder sb, String value, int place) {
    int count = 0;
    while (value.length() + count < place) {
        sb.append(" ");
        count++;
    }
    sb.append(value);
    return sb;
}}

问题出在哪里，我该如何解决？

我认为，我没有在 middleHeight 上设置正确的参数，   headerHeight ， footerHeight ，宽度和高度。

我还认为打印机的问题在于打印机只能以该长度打印。

或者我的代码中有问题要停止打印？还有另一种打印长期收据的方法吗？

我该如何解决？

您的帮助将不胜感激！