如何在JTextArea中打开文件并使用FileReader和FileWriter类进行写入和读取

时间：2011-11-28 03:34:22

标签： java swing jtextarea

我试图在JTextArea中打开一个文件然后写入并读取它。我终于使用FileReader在JTextArea中打开它，然后打破它尝试合并FileWriter。现在我再也无法在文本区域打开它。我看到过显示FileChooser打开特定文件的示例，但我希望用户能够传递变量，以便用户可以使用FileChooser打开他们浏览的任何文件。当我破坏代码时，我正在为我的OpenLister方法添加文件阅读器。将FileReader和FileWriter放在同一个ActionListener中是否常见？任何一个好的例子和建议的方向将非常感激。我复制了下面的代码。

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

public class ClassChooser extends JFrame implements ActionListener
{
//create a label
private JLabel response;
File file;
//menu tabs
private JMenu fileMenu;
private JMenu editMenu;
private JMenu helpMenu;
String line;
//create a file chooser
private JFileChooser fc;
 BufferedReader br;
//create a text area
JTextArea ta = new JTextArea();

//constructors
public ClassChooser
{
    //create scroll pane
    JScrollPane scrollPane = new JScrollPane(ta);

    ta.setText("Enter text to see scroll bars.");
    //create a panel
    JPanel content = new JPanel();
    content.setLayout(new BorderLayout());
    content.add(scrollPane, BorderLayout.CENTER);

    //call functions to create drop down menu's 
    createFileMenu();
    createEditMenu();
    createHelpMenu();

    //create menu bar and add drop down menu's
    JMenuBar menuBar = new JMenuBar();
    this.setJMenuBar(menuBar);
    menuBar.add(fileMenu);
    menuBar.add(editMenu);
    menuBar.add(helpMenu);


    this.setContentPane(content);
    this.setTitle("File Chooser");
    this.setVisible(true);
    this.setSize(600,250);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

 }

public void createFileMenu()
{
    JMenuItem item;

    fileMenu = new JMenu("File");

    item = new JMenuItem("New");
    item.addActionListener(this);
    fileMenu.add(item);

    item = new JMenuItem("Open");
    item.addActionListener(new OpenListener());
    fileMenu.add(item);

    item =  new JMenuItem("Save");
    item.addActionListener(this);
    fileMenu.add(item);

    item = new JMenuItem("Rename");
    item.addActionListener(this);
    fileMenu.add(item);

    item = new JMenuItem("Delete");
    item.addActionListener(this);
    fileMenu.add(item);

    item = new JMenuItem("Make Directory");
    item.addActionListener(this);
    fileMenu.add(item);
    fileMenu.addSeparator();

    item = new JMenuItem("Exit");
    item.addActionListener(this);
    fileMenu.add(item);

}
public void createEditMenu()
{
    JMenuItem item;

    editMenu = new JMenu("Edit");

    item = new JMenuItem("Cut");
    item.addActionListener(this);
    editMenu.add(item);

    item = new JMenuItem("Copy");
    item.addActionListener(this);
    editMenu.add(item);

    item = new JMenuItem("Paste");
    item.addActionListener(this);
    editMenu.add(item);

}
public void createHelpMenu()
{
    JMenuItem item;

    helpMenu = new JMenu("Help");

    item = new JMenuItem("Welcome");
    item.addActionListener(this);
    helpMenu.add(item);

    item = new JMenuItem("Help Contents");
    item.addActionListener(this);
    helpMenu.add(item);
}

private class OpenListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{       
      fc = new JFileChooser();
      // directories only to be selected
      fc.setFileSelectionMode(JFileChooser.FILES_ONLY);
      fc.setSelectedFile(fc.getCurrentDirectory() );
      fc.setDialogTitle("Directory Chooser");
      fc.setMultiSelectionEnabled(false);

      int retVal = fc.showOpenDialog(ClassChooser.this);
      //File file;

      if(retVal == fc.APPROVE_OPTION)
      {
         file = fc.getSelectedFile();

        try {
            br = new BufferedReader(new FileReader(file));
        } catch (FileNotFoundException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        try {
            line = br.readLine();
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
         while(line != null)
         {
             ta.append(line + "\n");
             try {
                line = br.readLine();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
         }
         }

  }
}

public static void main(String[] args)
{
   ClassChooser fce = new ClassChooser;
       String filename = File.separator + "tmp";

}

public void actionPerformed(ActionEvent e) 
{
// TODO Auto-generated method stub
 String menuName;

    menuName = e.getActionCommand();

    if(menuName.equals("Exit"))
    {
    System.exit(0);
    }
else
    {
    response.setText("Menu Item '" + menuName + "' is selected.");
    }   
}

}

1 个答案:

答案 0 :(得分：3)

您的代码实际上会打开文件，但您将在文本区域中附加，而不会清除以前加载的文件的内容。

因此，在OpenListener类actionPerformed方法中添加ta.setText("")作为第一个语句，然后继续加载文件内容。

代码：

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

public class ClassChooser extends JFrame implements ActionListener {
   // create a label
   private JLabel           response;
   File                 file;
   // menu tabs
   private JMenu            fileMenu;
   private JMenu            editMenu;
   private JMenu            helpMenu;
   String                   line;
   // create a file chooser
   private JFileChooser fc = null; 
   BufferedReader           br;
   // create a text area
   JTextArea                ta  = new JTextArea();
     private String currentFileBeingEdited = null;
   // constructors
   public ClassChooser() {
       // create scroll pane
       JScrollPane scrollPane = new JScrollPane(ta);
       ta.setText("Enter text to see scroll bars.");
       // create a panel
       JPanel content = new JPanel();
       content.setLayout(new BorderLayout());
       content.add(scrollPane, BorderLayout.CENTER);
       // call functions to create drop down menu's
       createFileMenu();
       createEditMenu();
       createHelpMenu();
       // create menu bar and add drop down menu's
       JMenuBar menuBar = new JMenuBar();
       this.setJMenuBar(menuBar);
       menuBar.add(fileMenu);
       menuBar.add(editMenu);
       menuBar.add(helpMenu);
       this.setContentPane(content);
       this.setTitle("File Chooser");
       this.setVisible(true);
       this.setSize(600, 250);
       this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 }

 public void createFileMenu() {
       JMenuItem item;
       fileMenu = new JMenu("File");
       item = new JMenuItem("New");
       item.addActionListener(this);
       fileMenu.add(item);
       item = new JMenuItem("Open");
       item.addActionListener(new OpenListener());
       fileMenu.add(item);
       item = new JMenuItem("Save");
       item.addActionListener(this);
       fileMenu.add(item);
       item = new JMenuItem("Rename");
       item.addActionListener(this);
       fileMenu.add(item);
       item = new JMenuItem("Delete");
       item.addActionListener(this);
       fileMenu.add(item);
       item = new JMenuItem("Make Directory");
       item.addActionListener(this);
       fileMenu.add(item);
       fileMenu.addSeparator();
       item = new JMenuItem("Exit");
       item.addActionListener(this);
       fileMenu.add(item);
 }

 public void createEditMenu() {
       JMenuItem item;
       editMenu = new JMenu("Edit");
       item = new JMenuItem("Cut");
       item.addActionListener(this);
       editMenu.add(item);
       item = new JMenuItem("Copy");
       item.addActionListener(this);
       editMenu.add(item);
       item = new JMenuItem("Paste");
       item.addActionListener(this);
       editMenu.add(item);
 }

public void createHelpMenu() {
    JMenuItem item;
    helpMenu = new JMenu("Help");
    item = new JMenuItem("Welcome");
    item.addActionListener(this);
    helpMenu.add(item);
    item = new JMenuItem("Help Contents");
    item.addActionListener(this);
    helpMenu.add(item);
    }

private class OpenListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
        //ADDED ONLY THIS LINE
        ta.setText("");
        fc = new JFileChooser();
        // directories only to be selected
        fc.setFileSelectionMode(JFileChooser.FILES_ONLY);
        fc.setSelectedFile(fc.getCurrentDirectory());
        fc.setDialogTitle("Directory Chooser");
        fc.setMultiSelectionEnabled(false);

        int retVal = fc.showOpenDialog(ClassChooser.this);
        // File file;

        if (retVal == fc.APPROVE_OPTION) {
            file = fc.getSelectedFile();
            currentFileBeingEdited = file.getAbsolutePath();
            try {
                br = new BufferedReader(new FileReader(file));
            } catch (FileNotFoundException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            try {
                line = br.readLine();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            while (line != null) {
                ta.append(line + "\n");
                try {
                    line = br.readLine();
                } catch (IOException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            }
        }

    }
}

public static void main(String[] args) {
    ClassChooser fce = new ClassChooser();
    String filename = File.separator + "tmp";

}

public void actionPerformed(ActionEvent e) {
    // TODO Auto-generated method stub
    String menuName;

    menuName = e.getActionCommand();

    if (menuName.equals("Exit")) {
        System.exit(0);
    } else if("Save".equalsIgnoreCase(menuName)){
        PrintWriter pw = null;
        try {
            pw = new PrintWriter(new File(currentFileBeingEdited));
            pw.println(ta.getText());
        } catch (FileNotFoundException e1) {
            e1.printStackTrace();
        } finally {
            if(pw != null){
                pw.close();
            }
        }

    } else {
        response.setText("Menu Item '" + menuName + "' is selected.");
    }
}

}
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