使用JFileChooser保存

问题描述

我正在使用JFileChooser和showSaveDialoge()和setSelectionMode(JfileChooser.DIRECTORIES_ONLY)来设置预选文件的保存位置和名称.

I am using a JFileChooser and the showSaveDialoge() and setSelectionMode(JfileChooser.DIRECTORIES_ONLY) to set where a preselected file will be saved and what it will be called.

我希望用户能够选择新版本的名称以及放置位置.我该怎么办?我也希望选择一个默认名称.

I want the user to be able to choose the name the new version, and where to put it. How do I go about this? I also wish to choose a default name.

推荐答案

我希望以下代码符合您的问题要求.您的问题中的条件在代码注释中得到回答.如果您需要澄清，请告诉我.

I hope the codes below implemented inline with your question requirements. The criteria in your question are answered in the code comment. If you need clarification, please let me know.

import java.awt.BorderLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

public class MyFileChooser extends JPanel implements ActionListener
{
    JButton saveButton;
    JTextArea content;
    JFileChooser jfc;

    private boolean docUpdate = false;
    private String default_filename = "default.txt";
    private String default_directory = "/home/foo/workspace";
    private int version = 0;

    public MyFileChooser()
    {
        super(new BorderLayout());

        content = new JTextArea(5, 20);
        content.setMargin(new Insets(5, 5, 5, 5));
        content.getDocument().addDocumentListener(new DocumentListener()
        {

            @Override
            public void removeUpdate(DocumentEvent e)
            {
                System.out.println("remove update");
                docUpdate = true;
            }

            @Override
            public void insertUpdate(DocumentEvent e)
            {
                System.out.println("insert update");
                docUpdate = true;
            }

            @Override
            public void changedUpdate(DocumentEvent e)
            {
                System.out.println("changed update");
                docUpdate = true;
            }
        });
        JScrollPane logScrollPane = new JScrollPane(content);

        jfc = new JFileChooser();

        /**
         * Set a initial default directory and a initial default filename here.
         */
        //fc.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
        jfc.setCurrentDirectory(new File(default_directory));
        jfc.setSelectedFile(new File(default_filename));
        jfc.addPropertyChangeListener(new PropertyChangeListener() {

            @Override
            public void propertyChange(PropertyChangeEvent evt)
            {
                if (docUpdate == true)
                {
                    /**
                     * User can use the suggested filename or remove the suggested,
                     * and enter a new filename.
                     * Here, we set to a new directory and of cause, user can select
                     * what is the directory he want.
                     */
                    jfc.setCurrentDirectory(new File("/home/foo"));
                    jfc.setSelectedFile(new File("default" + version + ".txt"));
                }
            }
        });

        saveButton = new JButton("Save a File...");
        saveButton.addActionListener(this);

        JPanel buttonPanel = new JPanel();
        buttonPanel.add(saveButton);

        add(buttonPanel, BorderLayout.PAGE_START);
        add(logScrollPane, BorderLayout.CENTER);
    }

    @Override
    public void actionPerformed(ActionEvent e)
    {

        int returnVal = jfc.showSaveDialog(MyFileChooser.this);
        if (returnVal == JFileChooser.APPROVE_OPTION)
        {
            File file = jfc.getSelectedFile();
            // save the file.
            BufferedWriter bw;
            try {
                bw = new BufferedWriter(new FileWriter(file));
                bw.write(content.getText());
                bw.flush();
            }
            catch (IOException e1)
            {
                e1.printStackTrace();
            }
            version++;

        }
        else
        {
            System.out.println("Save command cancelled by user. ");
        }
        content.setCaretPosition(content.getDocument().getLength());

    }

    private static void createAndShowGUI()
    {
        JFrame frame = new JFrame("FileChooserDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.add(new MyFileChooser());

        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {

            @Override
            public void run()
            {
                createAndShowGUI();
            }
        });
    }

}

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