java - 为我正在创建的 GUI 中的 JMenuItem "Copy"提供低级功能

Question

我正在创建一个具有 JMenuItems(例如复制和粘贴)的低级 GUI。我需要创建一个 selectText() 方法，用于复制已合并到 JScrollPane 中的 JTextArea 中的选定文本。我正在尝试找出我应该使用的代码。我尝试过使用 getSelectedText() 但总是返回“null”。我有一些操作仍然没有任何功能，或者显示一个消息对话框，显示“有效”，以知道我已经添加了 ActionEvent，但没有任何实际功能。最终，我尝试将功能添加到 JMenuItem“复制”中，以便我可以使用 JMenuItem“列表文件”打开文件(这只打开基本文件，例如 .txt)，然后复制 JTextArea 中显示的内容使用鼠标选择所需的文本，然后转到“工具”>“编辑”>“复制”，并使用 JMenuItem“复制”中集成的功能选择文本并使用名为 selectText() 的方法将其存储在字符串变量中。还要忽略 BasicFile 类中的一些方法，因为我从必须制作的另一个程序中重新使用了它。

这是我的代码:

MyJFrame.java

/*
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 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package MyJFrame;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GraphicsConfiguration;
import java.awt.HeadlessException;
import java.awt.event.ActionEvent;
import java.io.FileNotFoundException;
import javax.swing.AbstractAction;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.text.JTextComponent;

/**
 *
 * @author Alejandro
 */
public class MyJFrame extends JFrame{

    public MyJFrame(String title) throws HeadlessException {
       super(title);
       super.getContentPane().setBackground(Color.lightGray);
       super.setPreferredSize(new Dimension(800, 600));
       super.setLocation(500,300);
       super.pack();

       //CREATING MENU BAR
       JMenuBar menuBar = new JMenuBar();
       for(int i = 0; i < Constants.menus.length; i++)
       {
           JMenu newMenu = new JMenu(Constants.menus[i]);
           //CREATING MENU FOR FILE
           if(Constants.menus[i].equals("File"))
           {
               for(int fileItemCounter = 0; fileItemCounter < Constants.fileMenuChoices.length; fileItemCounter++)
               {
                   //ADDING SEPARATOR WHEN NEEDED
                   if(Constants.fileMenuChoices[fileItemCounter].equals("*"))
                   {
                       newMenu.addSeparator();
                   }
                   else if(Constants.fileMenuChoices[fileItemCounter].equals("New"))
                   {
                        JMenuItem newMenuItem = new JMenuItem(new AbstractAction("New") 
                        {
                            public void actionPerformed(ActionEvent e) 
                            {
                                // Button pressed logic goes here
                                MyJFrame childFrame = new MyJFrame("New File");
                                childFrame.setLocation(600, 400);
                            }
                        });
                        newMenu.add(newMenuItem);
                   }
                   else if(Constants.fileMenuChoices[fileItemCounter].equals("List Files"))
                   {
                       JMenuItem newMenuItem = new JMenuItem(new AbstractAction("List Files") 
                        {
                            public void actionPerformed(ActionEvent e) 
                            {
                                // Button pressed logic goes here
                                try
                                {
                                    BasicFile f = new BasicFile();
                                    DisplayText textToBeDisplayed = new DisplayText(f.getName(), f.getContents());
                                    JTextArea text = new JTextArea(textToBeDisplayed.getFileContents(),50, 50);
                                    JScrollPane pane = new JScrollPane(text);
                                    MyJFrame fileOpened = new MyJFrame(textToBeDisplayed.getFileName());
                                    fileOpened.add(pane);
                                    fileOpened.setLocation(600, 400);
                                }
                                catch(FileNotFoundException x)
                                {

                                }        
                            }
                        });
                        newMenu.add(newMenuItem);
                   }
                   else
                   {
                        JMenuItem newMenuItem = new JMenuItem(Constants.fileMenuChoices[fileItemCounter]);
                        newMenu.add(newMenuItem);
                   }
               }
           }
           //CREATING MENU FOR TOOLS
           if(Constants.menus[i].equals("Tools"))
           {
               for(int toolsItemCounter = 0; toolsItemCounter < Constants.toolsMenuChoices.length; toolsItemCounter++)
               {
                   //CREATING SUBMENU FOR MENU ITEM "EDIT"
                   if(Constants.toolsMenuChoices[toolsItemCounter].equals("Edit"))
                   {
                       JMenu newSubMenu = new JMenu(Constants.toolsMenuChoices[toolsItemCounter]);
                       for(int editMenuChoicesCounter = 0; editMenuChoicesCounter < Constants.editMenuChoices.length; editMenuChoicesCounter++)
                       {
                           if(Constants.editMenuChoices[editMenuChoicesCounter].equals("Copy"))
                           {
                                JMenuItem menuItem = new JMenuItem(new AbstractAction("Copy") 
                                {
                                    public void actionPerformed(ActionEvent e) 
                                    {
                                        // Button pressed logic goes here
                                        JOptionPane.showMessageDialog(null, "works");
                                    }
                                });
                                newSubMenu.add(menuItem);
                           }
                           else if(Constants.editMenuChoices[editMenuChoicesCounter].equals("Paste"))
                           {
                               JMenuItem menuItem = new JMenuItem(new AbstractAction("Paste") 
                                {
                                    public void actionPerformed(ActionEvent e) 
                                    {
                                        // Button pressed logic goes here
                                        JOptionPane.showMessageDialog(null, "works");
                                    }
                                });
                                newSubMenu.add(menuItem);
                           }
                                newMenu.add(newSubMenu);
                       }
                   }
                   else
                   {
                       JMenuItem newMenuItem = new JMenuItem(Constants.toolsMenuChoices[toolsItemCounter]);
                       newMenu.add(newMenuItem);
                   }
               }
           }
           menuBar.add(newMenu);
       }
       super.setJMenuBar(menuBar);
       super.setVisible(true);
    }

    public static void main(String[] args) {
       MyJFrame mainFrame = new MyJFrame("My First GUI");
    }
}

DisplayText.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package MyJFrame;

import javax.swing.JTextArea;

/**
 *
 * @author Alejandro
 */
public class DisplayText {
    String fileName;
    String fileContents;

    public DisplayText(String fileName, String fileContents) {
        this.fileName = fileName;
        this.fileContents = fileContents;
    }

    public String getFileName() {
        return fileName;
    }

    public String getFileContents() {
        return fileContents;
    }

//    public String selectText()
//    {
//        ;
//    }
}

BasicFile.java

 /*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package MyJFrame;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.LineNumberReader;
import java.io.StreamTokenizer;
import java.util.Scanner;
import javax.swing.JFileChooser;
import javax.swing.JOptionPane;

/**
 *
 * @author Alejandro
 */
public class BasicFile
{
    File f;
    File backupFile;

    public BasicFile()
    {
                    JFileChooser choose = new JFileChooser(".");
                    int status = choose.showOpenDialog(null);

                    try
                    {
                                    if (status != JFileChooser.APPROVE_OPTION) 
                                            throw new IOException();
                                    f = choose.getSelectedFile();
                                    if (!f.exists()) 
                                            throw new FileNotFoundException();
                    }
                    catch(FileNotFoundException e)
                    {
                                    display(e.toString(), "File not found ....");
                    }
                    catch(IOException e)
                    {
                                    display(e.toString(),  "Approve option was not selected");
                    }
    }

    void display(String msg, String s)
    {
                    JOptionPane.showMessageDialog(null, msg, s, JOptionPane.ERROR_MESSAGE);
    }

    // Other methods may be included

    String getContents() throws FileNotFoundException{
     String content = "";
     Scanner readFile = new Scanner(f);
     while(readFile.hasNext()){
         content = content + readFile.nextLine() + "\n";
     }
     return content;
    }

    long getFileSize(){
        return f.length();
    }

    String getPath(){
        return f.getPath();
    }

    String getName(){
        return f.getName();
    }

    String backUpFile(){
        return "File successfully backed up!";
    }

    String displayFileInfo(){
        File parentDirectory = new File(f.getParent());
        File[] filesAndDirectories = parentDirectory.listFiles();
        String filesAndDirectoriesInfo = "";
        for(File f : filesAndDirectories){
            filesAndDirectoriesInfo = filesAndDirectoriesInfo + f.getAbsolutePath() + "\n";
        }
        return "File name: " + f.getName() + "\nAbsolute Path: " + f.getAbsolutePath() + "\nFiles and Directories:\n"
                 + filesAndDirectoriesInfo + "\nFile Size: " + f.length() + " bytes";
    }


   void backupFile() throws FileNotFoundException
   {
        JOptionPane.showMessageDialog(null, "Please select or create a file for the backup", "File Backup", JOptionPane.INFORMATION_MESSAGE);
        JFileChooser backupChoose = new JFileChooser(".");
        int backupStatus = backupChoose.showSaveDialog(null);        
        try
        {
                        if (backupStatus != JFileChooser.APPROVE_OPTION) 
                                throw new IOException();
                        backupFile = backupChoose.getSelectedFile();
        }
        catch(IOException e)
        {
                        display(e.toString(),  "Approve option was not selected");
        }
        DataInputStream in = null;
        DataOutputStream out = null;
        try
        {
            in = new DataInputStream(new FileInputStream(f));
            out = new DataOutputStream(new FileOutputStream(backupFile));
            try
            {
                while (true)
                {
                    byte data = in.readByte();
                    out.writeByte(data);
                }
            }
            catch(EOFException e)
            {
                  JOptionPane.showMessageDialog(null, "File was successfully backed up!",
                                 "Complete", JOptionPane.INFORMATION_MESSAGE);
            }
            catch (IOException e)
            {
                JOptionPane.showMessageDialog(null, "File not found",
                                 "Error", JOptionPane.INFORMATION_MESSAGE);
            }
        }
        finally
        {
            try
            {
                in.close();
                out.close();
            }
            catch(Exception e)
            {
                display(e.toString(), "Error");
            }
        }
    }

   String countFile()
   {
        try
        {
            int wordCount = 0;
            int numberCount = 0;
            int lineCount = 1;
            int charCount = 0;
            int totalWords = 0;

            FileReader reader = new FileReader(f);
            StreamTokenizer st = new StreamTokenizer(reader);
            st.eolIsSignificant(true);
            st.whitespaceChars(0, ' ');
            st.wordChars('a','z');
            st.wordChars('A','Z');
            do{
                if(st.ttype == StreamTokenizer.TT_NUMBER){
                    numberCount++;
                    charCount++;
                }
                if(st.ttype == StreamTokenizer.TT_WORD){
                    charCount += st.sval.length();
                    wordCount++;
                }
                if(st.ttype == StreamTokenizer.TT_EOL){
                    lineCount++;
                }
                if(st.ttype == StreamTokenizer.TT_EOF){
                    break;
                }
            }while(st.nextToken() != StreamTokenizer.TT_EOF);
            reader.close();
            totalWords = numberCount + wordCount;
            return f.getName() + " has " + lineCount + " lines, " 
                    + totalWords + " words, " + numberCount + " numbers, " + charCount + " characters.  (Approximately)";
        }
        catch(IOException e)
        {
            display(e.toString(), "Error");
        }
        return "null";
   }

   public String findString(String line, String currentLine, String stringToSearch, LineNumberReader lnr) throws Exception  
    { 
      if(currentLine != null)  
      {       
        String s = currentLine.toLowerCase();   

        if(s.contains(stringToSearch.toLowerCase()))  
        {  
           line = line + "\nLine " + lnr.getLineNumber() + ": " + currentLine;  
        }  
        return findString(line, lnr.readLine(), stringToSearch, lnr );
      } 
       return line;
     }  

   String search() throws FileNotFoundException, IOException, Exception{
       String stringSearched = JOptionPane.showInputDialog("Enter string to search for: ");
       LineNumberReader lnr = new LineNumberReader(new FileReader(f));
       String results = findString("", lnr.readLine(), stringSearched, lnr);
       return results;
   }
}

Constants.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package MyJFrame;

/**
 *
 * @author Alejandro
 */
public interface Constants {

    public static final String[] menus = {"File","Tools","Help"};

    public static final String[] fileMenuChoices = {"New", "List Files","*", "Save As", "*", "Close"};

    public static final String[] toolsMenuChoices = {"Sort", "Search", "Edit"};

    public static final String[] editMenuChoices = {"Copy", "Paste"};

}

Answer 1

您应该考虑使用JTextArea的内置功能...

• JTextArea#copy
• JTextArea#cut
• JTextArea#paste

您可能还想看看 How to Use Actions