Java代码正在打印白页

Question

我必须使用热敏打印机 Sewoo SLK-TS400 打印收据。我正在制作一个字符串并想用打印机打印它。但它正在打印白页。我已经搜索了很多东西，但什么也没发生。

账单制作方法

package printprogram;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.swing.table.DefaultTableModel;

public class MakingBill {
public static void main(String[] args)
{

  DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
  DateFormat timeFormat = new SimpleDateFormat("HH:mm");
  Date date = new Date();
  Date time = new Date();
  String Date = dateFormat.format(date);
  String Time = timeFormat.format(time);
  String Header = 
        "   ****Super Market****       \n"
        + "Date: "+Date+"     Time: "+Time+"\n"
        + "---------------------------------\n"
        + "Name          Qty    Rate     Amt\n"
        + "---------------------------------\n";

  String amt  =    
        "\n \n \nTotal Amount = "   +"\n"
        + "Tax ="       + "\n"
        + "*********************************\n"
        + "Thank you. \n";

  String bill = Header;
    System.out.println(bill);

  Main mn = new Main();
  mn.printCard(bill);    
 }
}

以及打印账单的类

package printprogram;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.print.PageFormat;
import java.awt.print.Printable;
import java.awt.print.PrinterException;
import java.awt.print.PrinterJob;

public class Main {

public static void printCard(final String bill) {
    Printable contentToPrint = new Printable() {
        @Override
        public int print(Graphics graphics, PageFormat pageFormat, int page)       throws PrinterException {
            if (page > 0) {
                return NO_SUCH_PAGE;
            }
            pageFormat.setOrientation(PageFormat.LANDSCAPE);
            Graphics2D g2d = (Graphics2D) graphics.create();

            g2d.setPaint(Color.black);
            g2d.setFont(new Font("Arial", Font.BOLD, 10));
            g2d.translate(pageFormat.getImageableX(), pageFormat.getImageableX());

            g2d.drawString(bill, 0, 0); 

            return PAGE_EXISTS;
        }
    };

    PrinterJob job = PrinterJob.getPrinterJob();
    job.setPrintable(contentToPrint);
    //You can show a print dialog before printing by job by wrapping the following blocks with a conditional statement if(job.printDialog()){...}
    try {
        job.print();
    } catch (PrinterException e) {
        System.err.println(e.getMessage());
    }

  }
}

请帮忙。我是java新手。

Answer 1

首先我想说抱歉，这么长时间才有人回答您的问题。现在进入主题。

您的代码存在一些问题，但它们仅出现在 Main.java

1. 如果您有代码 g2d.translate(pageFormat.getImageableX(), pageFormat.getImageableX());，则调用 getImageableX() 两次，而不是 g2d.translate(pageFormat.getImageableX(), pageFormat.getImageableY());。

2. 在尝试绘制字符串 bill 时，您似乎没有意识到 drawString() 无法处理新行 \n。要解决此问题，您可以使用 FontMetrics 。例如:

   private void drawString(Graphics g, String text, int x, int y) {
       for (String line : text.split("\n"))
           g.drawString(line, x, y += g.getFontMetrics().getHeight());
   }
   

为了确保下面提供的代码有效，我对其进行了测试并且可以正确打印。

<小时/>

这会给你留下如下所示的代码

Main.java

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.print.PageFormat;
import java.awt.print.Printable;
import java.awt.print.PrinterException;
import java.awt.HeadlessException;
import java.awt.print.PrinterJob;

public class Main {
    private void drawString(Graphics g, String text, int x, int y) {
        for (String line : text.split("\n"))
            g.drawString(line, x, y += g.getFontMetrics().getHeight());
    }

    public Main(String bill) {
        Printable contentToPrint = new Printable() {
            @Override
            public int print(Graphics graphics, PageFormat pageFormat, int page) throws PrinterException {
                if (page > 0) {
                    return NO_SUCH_PAGE;
                }
                pageFormat.setOrientation(PageFormat.LANDSCAPE);
                Graphics2D g2d = (Graphics2D)graphics;

                g2d.setPaint(Color.black);
                g2d.setFont(new Font("Arial", Font.BOLD, 10));
                g2d.translate(pageFormat.getImageableX(), pageFormat.getImageableY());

                drawString(g2d, bill, 0, 0); 

                return PAGE_EXISTS;
            }
        };

        PrinterJob job = PrinterJob.getPrinterJob();
        job.setPrintable(contentToPrint);
        try {
            job.printDialog();
            job.print();
        } catch (PrinterException e) {
            System.err.println(e.getMessage());
        } catch (HeadlessException e) {
            System.err.println(e.getMessage());
        }
    }
}

MakingBill.java

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.swing.table.DefaultTableModel;

public class MakingBill {
    public static void main(String[] args) {
        DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
        DateFormat timeFormat = new SimpleDateFormat("HH:mm");
        Date date = new Date();
        Date time = new Date();
        String Date = dateFormat.format(date);
        String Time = timeFormat.format(time);
        String Header = 
            "   ****Super Market****       \n"
            + "Date: "+Date+"     Time: "+Time+"\n"
            + "---------------------------------\n"
            + "Name          Qty    Rate     Amt\n"
            + "---------------------------------\n";

        String amt  =    
            "\n \n \nTotal Amount = "   +"\n"
            + "Tax ="       + "\n"
            + "*********************************\n"
            + "Thank you. \n";

        String bill = Header;
        System.out.println(bill);

        Main mn = new Main(bill);
    }
}

这会产生如下所示的输出:

要使所有内容按照您的意愿排列，请添加额外的 - 或更改字体。