Having problem with JTextArea

Question

grga4life 0 Newbie Poster

14 Years Ago

Hello everyone,I have little problem over here with my work. It gives null pointer about JTextArea in ActionListener. Could anyone help me,please? Thanks in advance
Here's code:

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

import javax.swing.*;

/**
 * @author Nikola
 * 
 */

public class FileListener implements ActionListener {

    private JMenuItem exit;
    private JMenuItem new1, open, save, saveas, wordcount, fileviewer;
    private JTextArea area;
    private JTextField field;
    private JFileChooser fileChoose;

    public FileListener(JMenuItem exit, JMenuItem wordcount, JTextArea area,
            JTextField field, JMenuItem open, JMenuItem save, JMenuItem saveas) {
        this.exit = exit;
        this.wordcount = wordcount;
        this.area = area;
        this.field = field;
        this.open = open;
        this.save = save;
        this.saveas = saveas;
    }

    @Override
    public void actionPerformed(ActionEvent e) {

        if (e.getSource() == exit) {
            System.exit(0);
        }

        else if (e.getSource() == wordcount) {
            if (area.getText().equals("")) {
                JOptionPane.showMessageDialog(null, "Text file is empty",
                        "Message", JOptionPane.ERROR_MESSAGE);
            }

            else {

                String in = area.getText();

                String[] words = in.split(" "); // separate string around spaces
                int count = words.length; // count number of wotrds

                JOptionPane.showMessageDialog(null, "The number of words is:  "
                        + count, "WordCount", JOptionPane.INFORMATION_MESSAGE);
            }

        }

        else if (e.getSource() == new1) {
            area.setText("");
            // field.setEditable(true);
            field.setText("");
        }

        else if (e.getSource() == open) {

            int result = fileChoose.showOpenDialog(area);
            File file = fileChoose.getSelectedFile();
            if (file != null && result == JFileChooser.APPROVE_OPTION) {
                try {
                    // open file
                    BufferedReader in = new BufferedReader(new FileReader(file));
                    StringBuffer sb = new StringBuffer(); // holds the incoming
                                                            // data

                    // read all data from file
                    String line = null;
                    while ((line = in.readLine()) != null) {
                        sb.append(line + "\n");
                    }

                    // done getting data, place it in the text area
                    area.setText(sb.toString());
                } catch (IOException ioe) {
                    // unexpected problem as file was found
                    System.out.println(ioe.getMessage());
                    ioe.printStackTrace();
                }
            } // end if

        }

        else if (e.getSource() == save) {
            String fileName = field.getText();
            File newFile = new File(fileName);

            String whatIsIn = area.getText();

            try {

                if (newFile.exists()) {
                    FileWriter fos = new FileWriter(newFile);
                    fos.write(whatIsIn);
                    fos.close();

                }

            } catch (IOException ioe) {
                ioe.printStackTrace();
            }

        }

        else if (e.getSource() == saveas) {

            int result = fileChoose.showSaveDialog(area);
            File file = fileChoose.getSelectedFile();
            if (file != null && result == JFileChooser.APPROVE_OPTION)
                try {
                    BufferedWriter out = new BufferedWriter(
                            new FileWriter(file));
                    out.write(area.getText());
                    out.close();
                } catch (IOException ioe) {
                    ioe.printStackTrace();
                }

            String setNameFile = file.getName();
            field.setText(setNameFile);

        }

    }

}




  import javax.swing.*;

   import java.awt.*;
import java.awt.event.*;


public class FileViewer extends JFrame
{
     private JTextField field;
    private JTextArea area;
     private JLabel name;
     private JMenu file,tools,help;
     private JButton setfont;
     private JMenuItem new1,open,save,saveas,exit,wordcount,fileviewer;
     private JComboBox font,size;
     private JMenuBar bar;
     private JPanel jp1,jp2,jp3,jp4,jp5,jp6;
    // private JFileChooser jf;

    public FileViewer()
    {
        setTitle("FileViewer");
        setLocation(250,200);
        setSize(640,505);   
        setResizable(false);
        setLayout(new BorderLayout());

        bar=new JMenuBar();
        setJMenuBar(bar);

        file=new JMenu("File");
        bar.add(file);

        tools=new JMenu("Tools");
        bar.add(tools);

        help=new JMenu("Help");
        bar.add(help);

        new1= new JMenuItem("New");
        new1.setMnemonic('N');
        file.add(new1);

        open=new JMenuItem("Open");
        open.setMnemonic('O');
        file.add(open);

        save=new JMenuItem("Save");
        save.setMnemonic('S');
        file.add(save);

        saveas=new JMenuItem("Save as");
        saveas.setMnemonic('S');
        file.add(saveas);

        exit=new JMenuItem("Exit");
        exit.setMnemonic('E');
        file.add(exit);

        wordcount=new JMenuItem("Word Count");
        wordcount.setMnemonic('W');
        tools.add(wordcount);

        fileviewer=new JMenuItem("About");
        fileviewer.setMnemonic('A');
        help.add(fileviewer);

        jp1=new JPanel();
        add(jp1,"West");

        area=new JTextArea(25,40);
        area.setLineWrap(true);
        area.setWrapStyleWord(true);
        jp1.add(area);

        //Panel for East
        jp2=new JPanel();
        add(jp2,"East");
        jp2.setLayout(new BorderLayout(174,174));

        String[] strfont= {"Regular","Italic","Bold","Bold Italic"};
        font=new JComboBox(strfont);
        Object obj1 = font.getSelectedItem();
        jp2.add(font,"North");

        String[] strsize= {"10","12","15"};
        size=new JComboBox(strsize);
        Object obj2 = size.getSelectedItem();

        jp2.add(size,"Center");

        setfont=new JButton("Set Font");
        setfont.setMnemonic('S');
        jp2.add(setfont,"South");

        //South
        jp3=new JPanel();
        add(jp3,"South");

        name=new JLabel("File Name: ");
        jp3.add(name);

        field=new JTextField(10);
        field.setEditable(false);
        jp3.add(field);

        // help listener
        HelpListener help = new HelpListener(fileviewer);
        fileviewer.addActionListener(help); // add to help listener

        // file listener

        FileListener listening = new FileListener(exit, wordcount,area,field,open,save,saveas);
        exit.addActionListener(listening);
        wordcount.addActionListener(listening);
        new1.addActionListener(listening);
        open.addActionListener(listening);
        save.addActionListener(listening);
        saveas.addActionListener(listening);
        //area.addActionListener(listening);
        // TODO  setfont.addActionListener(listening);
        //jf.addActionListener(listening);



/*        Listener8 listening= new Listener8(field, area, setfont, new1, open, save, saveas, exit, wordcount, fileviewer,font,size, jf);

        field.addActionListener(listening);



        fileviewer.addActionListener(listening);
        font.addActionListener(listening);
        //size.addActionListener(listening);
    //  jf.addActionListener(listening);
        */

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);

    }

    public static void main(String[]args)
    {
        FileViewer int8=new FileViewer();
    }

}

and here is the ERROR that shows :

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

at FileListener.actionPerformed(FileListener.java:113)

at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2028)

at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2351)

at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)

at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)

at javax.swing.AbstractButton.doClick(AbstractButton.java:389)

at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:809)

at com.apple.laf.AquaMenuItemUI.doClick(AquaMenuItemUI.java:137)

at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:850)

at java.awt.Component.processMouseEvent(Component.java:6375)

at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)

at java.awt.Component.processEvent(Component.java:6140)

at java.awt.Container.processEvent(Container.java:2083)

at java.awt.Component.dispatchEventImpl(Component.java:4737)

at java.awt.Container.dispatchEventImpl(Container.java:2141)

at java.awt.Component.dispatchEvent(Component.java:4565)

at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4619)

at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4280)

at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4210)

at java.awt.Container.dispatchEventImpl(Container.java:2127)

at java.awt.Window.dispatchEventImpl(Window.java:2482)

at java.awt.Component.dispatchEvent(Component.java:4565)

at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:684)

at java.awt.EventQueue.access$000(EventQueue.java:85)

at java.awt.EventQueue$1.run(EventQueue.java:643)

at java.awt.EventQueue$1.run(EventQueue.java:641)

at java.security.AccessController.doPrivileged(Native Method)

at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)

at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)

at java.awt.EventQueue$2.run(EventQueue.java:657)

at java.awt.EventQueue$2.run(EventQueue.java:655)

at java.security.AccessController.doPrivileged(Native Method)

at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)

at java.awt.EventQueue.dispatchEvent(EventQueue.java:654)

at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)

at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)

at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

java:swing

3 Contributors
4 Replies
185 Views
53 Minutes Discussion Span
Latest Post 14 Years Ago Latest Post by NormR1

Dani AI

Generated 6 Months Ago

Short answer: the NullPointerException on line 113 is almost certainly caused by fileChoose being null — it’s declared in FileListener but never created or passed in. As suggested, inspect the variables used on that line; in this code the call fileChoose.showOpenDialog(...) (or showSaveDialog) will NPE if fileChoose is null. is also correct that you should pass a proper parent component (the top-level JFrame) to the chooser dialog rather than relying on a child component.

Concrete fixes and safe patterns:

Initialize the chooser (simple fix inside FileListener):

// inside the FileListener constructor
this.fileChoose = new JFileChooser();

Or supply the chooser (and the parent frame) from the window that creates the listener:

// FileViewer: new FileListener(this, new JFileChooser(), ...);
// FileListener fields:
private final Component parent;
private final JFileChooser fileChoose;
public FileListener(Component parent, JFileChooser chooser, ...) {
    this.parent = parent;
    this.fileChoose = chooser;
    ...
}
// use fileChoose.showSaveDialog(parent);

Fix the save-as logic: only call file.getName() and update field when the user actually approved the dialog. Use try-with-resources to write the file so streams are always closed.

Other notes: new1 in FileListener is never set (you either need to pass it in or remove that check), but that alone wouldn’t throw at the showDialog line. Construct the GUI on the EDT (SwingUtilities.invokeLater), and add a quick debug print or debugger check at the suspicious line if uncertain — printing the local variables will immediately reveal which one is null.

All 4 Replies

NormR1 580 Posting Sage

14 Years Ago

It gives null pointer

Look at line 113 and find the variable with the null value. Then backtrack in the code to see why that variable does not have a valid value.

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grga4life 0 Newbie Poster · Answer 1 · 2012-06-25T12:11:22+00:00

Yes,I know there's problem in that line but I can not see the problem and I do not understand why is it?

delta_frost 0 Newbie Poster · Answer 2 · 2012-06-25T12:17:55+00:00

A JFileChooser's showSaveDialog method accepts a Component reference.This must refer to the parent JFrame over which the Dialog is created.

NormR1 580 Posting Sage Team Colleague · Answer 3 · 2012-06-25T12:26:13+00:00

I do not understand why is it?

There is a variable on that line with a null value causing the NPE.
If you can not see what variable has the null value, add a println() statement just before that line that prints out the values of all the variables used on that line so you can see which variable has the null value.

Having problem with JTextArea

Dani AI

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