Question

我一直关注Oracle Java文档网站上的How to Print Text教程。但是，当我尝试将一些代码实现到我的代码中时，我收到了一个错误。

javac PrintableForms.java
PrintableForms.java:165: error: incompatible types: PrintableForms cannot be converted to Component
JOptionPane.showMessageDialog(this, msg, "Printing", type);

我的代码是

import javax.swing.*;
import java.awt.*;
import java.io.*;
import javax.swing.*;
import java.awt.print.PrinterException;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import javax.swing.*;
import java.text.MessageFormat;
import javax.xml.transform.Source;

public class PrintableForms
{
    JFrame myMainWindow = new JFrame("This is my title");

    JPanel  firstPanel = new JPanel();

    JButton btnDoc1 = new JButton();
    JButton btnP1 = new JButton();

    GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
    String []fontFamilies = ge.getAvailableFontFamilyNames();
    Font FontT5 = new Font("SansSerif", Font.BOLD, 50);
    ///////////
    JCheckBox backgroundCheck = new JCheckBox();
    JCheckBox interactiveCheck = new JCheckBox();
    JTextArea text = new JTextArea();
    JTextField headerField = new JTextField();
    JTextField footerField = new JTextField();

    public void runGUI()
    {
        myMainWindow.setBounds(10, 10, 1200, 500);
        myMainWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        myMainWindow.setLayout(new GridLayout(1,1));

        createFirstPanel();

        myMainWindow.getContentPane().add(firstPanel);

        myMainWindow.setVisible(true);
        load(text, "Athlete.txt");
    }

    public void createFirstPanel()
    {
        firstPanel.setLayout(null);

        btnDoc1.setLocation(10,120);
        btnDoc1.setSize(900,50);
        btnDoc1.setText("Update Personal Information");
        btnDoc1.setFont(FontT5);
        firstPanel.add(btnDoc1);

        btnP1.setLocation(910,120);
        btnP1.setSize(250,50);
        btnP1.setText("Print");
        btnP1.setFont(FontT5);
        btnP1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                print(evt);
            }
        });
        firstPanel.add(btnP1);


        footerField.setText("Page {0}");
        headerField.setText("Athlete Form");
        backgroundCheck.setSelected(true);
        interactiveCheck.setSelected(true);
    }

    private void load(JTextArea comp, String fileName) {
        try {
            comp.read(
                new InputStreamReader(
                    getClass().getResourceAsStream(fileName)),
                null);
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    private void print(java.awt.event.ActionEvent evt) 
    {
        MessageFormat header = createFormat(headerField);
        MessageFormat footer = createFormat(footerField);
        boolean interactive = interactiveCheck.isSelected();
        boolean background = backgroundCheck.isSelected();

        PrintingTask task = new PrintingTask(header, footer, interactive);
        if (background) 
        {
            task.execute();
        } 

        else 
        {
            task.run();
        }
    }

    private class PrintingTask extends SwingWorker<Object, Object> 
    {
        private final MessageFormat headerFormat;
        private final MessageFormat footerFormat;
        private final boolean interactive;
        private volatile boolean complete = false;
        private volatile String message;
        JTextArea text = new JTextArea();

        public PrintingTask(MessageFormat header, MessageFormat footer, boolean interactive) 
        {
            this.headerFormat = header;
            this.footerFormat = footer;
            this.interactive = interactive;
        }

        @Override
        protected Object doInBackground() {
            try {
                complete = text.print(headerFormat, footerFormat,
                        true, null, null, interactive);
                message = "Printing " + (complete ? "complete" : "canceled");
            } catch (PrinterException ex) {
                message = "Sorry, a printer error occurred";
            } catch (SecurityException ex) {
                message =
                    "Sorry, cannot access the printer due to security reasons";
            }
            return null;
        }

        @Override
        protected void done() {
            message(!complete, message);
        }
    }

    private MessageFormat createFormat(JTextField source) {
        //String text = new Scanner( new File("Athlete.txt") ).useDelimiter("\\A").next();
        String text = source.getText();
        if (text != null && text.length() > 0) {
            try {
                return new MessageFormat(text);
            } catch (IllegalArgumentException e) {
                error("Sorry, this format is invalid.");
            }
        }
        return null;
    }

    private void message(boolean error, String msg) 
    {
        int type = (error ? JOptionPane.ERROR_MESSAGE :
                            JOptionPane.INFORMATION_MESSAGE);
        JOptionPane.showMessageDialog(this, msg, "Printing", type);
    }

    private void error(String msg) 
    {
        message(true, msg);
    }

    public static void main(String[] args)
    {
        PrintableForms pf = new PrintableForms();
        pf.runGUI();
    }
}

我试图这样做，当我点击一个按钮时，btnP1在这种情况下，它会打开一个对话框，然后允许您打印预设文档。在此代码中，该文档是Athlete.txt，所有内容都是This is a test

我会帮助解决这个问题，谢谢

Answer 1

您应该扩展组件类或创建组件类型对象并作为参数传递而不是此，因为

JOptionPane.showMessageDialog(this, msg, "Printing", type);

第一个参数是组件类型，您将类型 PrintableForms 的参数传递为此。

Answer 2

您可以传递框架对象，该对象是您想要显示对话框窗口时创建的主窗口。

如下所示。

JOptionPane.showMessageDialog(myMainWindow, msg, "Printing", type);

Answer 3

尝试实施Printable界面。

尝试创建打印功能时出错

3 个答案: