Re: need advice using swing jfilechooser

Knute Johnson <>
Wed, 27 Oct 2010 20:16:15 -0700
On 10/27/2010 10:06 AM, jimgardener wrote:

I created a gui app in which I have two jfilechooser widgets ,one to
select a file and other to select a different directory.I want the
selected filename and selected directory name to be displayed in a
textarea.If no selection is made ,i want to display an error message
I coded like this

class MyView extends JFrame {
     private JFileChooser filechooser;
     private JFileChooser dirchooser;
     private JTextArea resultfield;
    ...//and many jpanels to contain these widgets above
      //and ok,quit buttons
    public MyView(MyModel model){
    super("top frame");
    public void createAndAddAllWidgets(){
    filechooser=new JFileChooser("Select imagefile");
    dirchooser=new JFileChooser();
    //similarly adds textarea and needed ok, quit buttons
    public String getSelectedFile(){
    public String getSelectedFolder(){
   public void displayMessage(String msg){
    public void addOKButtonListener(ActionListener okl){
    public void addQuitButtonListener(ActionListener qbl){

}//end of MyView class

class MyController{
    private MyModel model;
    private MyView view;
    public MyController(MyModel m,MyView v ){
        view.addOKButtonListener(new OKButtonListener());
        view.addQuitButtonListener(new QuitButtonListener());
         class OKButtonListener implements ActionListener {
         public void actionPerformed(ActionEvent e) {
          String fileselection=view.getSelectedFile();
          String folderselection=view.getSelectedFolder();

          String result=model.processSelections(fileselection,
    }//end inner class
    class QuitButtonListener implements ActionListener {
         public void actionPerformed(ActionEvent e) {
    }//end inner class
}//end of MyController class

class MyModel{
    public String processSelections(String filename,String foldername){
        String result="you selected file:"+filename+" you selected
        return result;
}//end of MyModel class

What I couldn't figure out was how to code the logic in MyView's
getSelectedFile(),getSelectedFolder() methods..
I can get the selected file name string as ,

filechooser.getSelectedFile().getPath() and
the selected folder name as

But,how should I deal with the situation when no file is selected or
no folder is selected?Should I return an empty string from the method ?
How can I display an error message if both happen at the same time?
I need to display the result from MyModel's processSelections() if
selections are made.I am not sure how I should do this.Should I define
a new Exception for these empty selection cases? or should I create
StringBuffer and append messages into it, and use it when I call
MyView's displayMessage() ?
If anyone can help me here ,it would be nice.

You didn't say what you wanted your program to do and the two
JFileChoosers didn't make a lot of sense. They are designed to allow
you to move through the directories and select the file you want. So
here is a simple program to select, load and display an image file.
There are a lot of ways to go about this but this is pretty simple and
covers a lot of things that can prove to be problematic when you first
try them. In this example if you don't select a file, nothing happens.
  If you successfully pick one then it will be displayed on the JPanel.
  If there is an error, a dialog is displayed with the error information.

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.imageio.*;
import javax.swing.*;
import javax.swing.filechooser.*;

public class test extends JPanel {
     // create this now so there won't be a delay on first opening
     private final JFileChooser fc = new JFileChooser();
     private final AbstractAction loadAction;

     private BufferedImage bi;

     public test() {
         // set a default size for the JPanel
         setPreferredSize(new Dimension(640,480));
         // put a title on the JFileChooser dialog
         fc.setDialogTitle("Select Image File");
         // set a filefilter to show only directories and image files
         fc.addChoosableFileFilter(new FileNameExtensionFilter(
          "Image Files","jpg","jpeg","gif","png"));
         // create the action for the load button
         loadAction = new LoadAction();

     public void paintComponent(Graphics g) {
         // clear the background
         // draw the image

     public class LoadAction extends AbstractAction {
         public LoadAction() {
             // label for the button
             putValue(NAME,"Load Image");

         public void actionPerformed(final ActionEvent ae) {
             // show the file chooser dialog
             int option = fc.showOpenDialog(test.this);

             if (option == JFileChooser.CANCEL_OPTION) {
                 // nothing to do here
             } else if (option == JFileChooser.APPROVE_OPTION) {
                 try {
                     // read the image file
                     bi =;
                     // resize the JPanel to the image
                     test.this.setPreferredSize(new Dimension(
                     // cause it to be re-layed out
                     // repaint it
                 } catch (IOException ioe) {
                     // display the io exception in a dialog
             } else if (option == JFileChooser.ERROR_OPTION) {
                 // display an error dialog
                  "ERROR READING IMAGE FILE","ERROR!",

     public static void main(String[] args) {
         EventQueue.invokeLater(new Runnable() {
             public void run() {
                 // create the frame
                 JFrame f = new JFrame();
                 // create the panel to show the image
                 test t = new test();
                 // wrap in a JScrollPane and add to frame
                 f.add(new JScrollPane(t),BorderLayout.CENTER);
                 // put the button on the frame
                 f.add(new JButton(t.loadAction),BorderLayout.SOUTH);
                 // display the frame


Knute Johnson
email s/nospam/knute2010/

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