Question

我正在尝试用Java编写文本编辑器应用程序。以下程序读取一个文本文件，然后通过BufferedReader方法显示它。但是，在这一点上我完全被困住了。可以在JFrame窗口中编辑显示的文本。但是在编辑后，我不知道如何关闭并保存编辑后的文件（即，如何合并事件处理程序，然后保存编辑后的文本）。

我已经尝试了很多事情，但是非常感谢您从这一点开始的进步。我是Java的新手，所以也许我程序的整个结构是错误的-任何帮助都值得赞赏。主程序在这里，随后是调用的显示面板创建者。该程序将弹出一个窗口，其中包含放置在目录中的名为text.txt的任何文本文件。

主要：

import java.io.*;
import java.util.ArrayList;
import static java.lang.System.out;
public class testApp4 {
    public static void main(String args[]) {
        ArrayList<String> listToSend = new ArrayList<String>();
        String file = "text.txt";
        try (BufferedReader br = new BufferedReader(new FileReader(file))) 
        {
            String line;
            while ((line = br.readLine()) != null) {
               listToSend.add(line);
            }
        br.close();
        }
        catch(FileNotFoundException e)
        {
            out.println("Cannot find the specified file...");
        }
        catch(IOException i)
        {
            out.println("Cannot read file...");
        }
        new DisplayPanel(listToSend);
    }
}

显示面板创建者：

import java.awt.Font;
import java.util.ArrayList;
import javax.swing.JFrame;// javax.swing.*;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JScrollPane;
import javax.swing.ScrollPaneConstants;

public class DisplayPanel {
    public DisplayPanel(ArrayList<String> list) //constructor of the DisplayGuiHelp object that has the list passed to it on creation
    {
        JTextArea theText = new JTextArea(46,120); //120 monospaced chrs
        theText.setFont(new Font("monospaced", Font.PLAIN, 14));
        theText.setLineWrap(true);
        theText.setEditable(true);
        for(String text : list)
        {
            theText.append(text + "\n"); //append the contents of the array list to the text area
        }
        JScrollPane scroll = new JScrollPane(theText);
        scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

        JPanel mainPanel = new JPanel();
        mainPanel.add(scroll);

        final JFrame theFrame = new JFrame();
        theFrame.setTitle("textTastico");
        theFrame.setSize(1100, 1000);
        theFrame.setLocation(550, 25);
        theFrame.add(mainPanel); //add the panel to the frame
        theFrame.setVisible(true);

        System.out.print(theText.getText()); //double check output!!!

    }
}

Answer 1

一种解决方法是更改窗口关闭的默认行为，并添加一个捕获窗口关闭事件的WindowListener并在那里保存。

可以在DisplayPanel类中添加一个简单示例（在创建jFrame对象之后）：

    theFrame.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
    theFrame.addWindowListener(new WindowAdapter() {
        @Override
        public void windowClosing(WindowEvent e) {
            super.windowClosing(e);
            String[] lines = theText.getText().split("\\n");
            try (BufferedWriter writer = new BufferedWriter(new FileWriter("newfile.txt"))) {
                for (String line : lines)
                    writer.write(line + "\n");
            } catch (IOException i) {
                System.out.println("Cannot write file...");
            }

            System.out.println("File saved!");
            System.exit(0);
        }
    });

以上代码将在关闭窗口时将更改后的文本保存到文件newfile.txt中。

在上面的示例中，可能不需要拆分成几行；您可能只通过执行writer.write(theText.getText());就可以得到正确的输出。主要的收获应该是使用WindowAdapter。

一些相关文档：

How to Write Window Listeners

Answer 2

以下是使用JButton来触发事件保存文本文件的示例。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import java.io.*;

public class DisplayPanel {

    public static String textFilePath = // adjust path as needed
            "C:\\Users\\Andrew\\Documents\\junk.txt";
    private JComponent ui = null;
    private JFrame frame;
    private JTextArea theText;
    private JButton saveButton;
    private ActionListener actionListener;
    File file;

    DisplayPanel(File file) {
        this.file = file;
        try {
            initUI();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    private void saveText() {
        Writer writer = null;
        try {
            writer = new FileWriter(file);
            theText.write(writer);
        } catch (IOException ex) {
            ex.printStackTrace();
        } finally {
            try {
                writer.close();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }

    public final void initUI() throws FileNotFoundException, IOException {
        if (ui != null) {
            return;
        }

        ui = new JPanel(new BorderLayout(4, 4));
        ui.setBorder(new EmptyBorder(4, 4, 4, 4));

        theText = new JTextArea(20, 120); //120 monospaced chrs
        theText.setFont(new Font(Font.MONOSPACED, Font.PLAIN, 14));
        theText.setLineWrap(true);
        theText.setEditable(true);
        JScrollPane scroll = new JScrollPane(theText);
        scroll.setVerticalScrollBarPolicy(
                ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

        ui.add(scroll);

        saveButton = new JButton("Save");
        ui.add(saveButton, BorderLayout.PAGE_START);

        actionListener = (ActionEvent e) -> {
            saveText();
        };
        saveButton.addActionListener(actionListener);

        Reader reader = new FileReader(file);
        theText.read(reader, file);
    }

    public void createAndShowGUI() {
        frame = new JFrame(this.getClass().getSimpleName());
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.setLocationByPlatform(true);

        frame.setContentPane(getUI());
        frame.pack();
        frame.setMinimumSize(frame.getSize());

        frame.setVisible(true);
    }

    public JComponent getUI() {
        return ui;
    }

    public static void main(String[] args) {
        Runnable r = () -> {
            try {
                UIManager.setLookAndFeel(
                        UIManager.getSystemLookAndFeelClassName());
            } catch (Exception useDefault) {
            }
            File file = new File(textFilePath);
            DisplayPanel o = new DisplayPanel(file);
            o.createAndShowGUI();
        };
        SwingUtilities.invokeLater(r);
    }
}

如何将已编辑的文本文件保存在JTextArea中？

2 个答案: