Error in making image viewer

Question

I am actually trying to make a simple image viewer using Java. It includes a label and three buttons. Two of these buttons act as left and right arrow keys for navigation and 3rd is an open button to select a directory. However, when I click on open only the first JPG image is viewed and that too unscaled . If I click on the forward button, the navigation does not happen.

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


public class picframe extends Thread implements ActionListener
{
  JTree tr;
  JScrollPane jsp;
  JFrame f;
  JButton b1,b2,b3;
  JLabel lab;
  File fl;
  File[] flist;
  ImageIcon ig;
  int k,j=0;
  FileDialog fdial;
  String str;

  picframe()
  {
    f=new JFrame("My Frame");
    f.setVisible(true);
    f.setLayout(null);


    lab=new JLabel();
    lab.setBounds(100,50,1166,500);
    f.add(lab);

    b1=new JButton(" <| ");
    b1.setBounds(486,600,100,30);
    b1.setEnabled(false);
    f.add(b1);
    b1.addActionListener(this);



    b2=new JButton(" |> ");
    b2.setBounds(786,600,100,30);
    f.add(b2);
    b2.setEnabled(false);
    b2.addActionListener(this);

    b3=new JButton("Open");
    b3.setBounds(633,650,100,30);
    f.add(b3);
    b3.addActionListener(this);

    f.pack();
    f.setSize(1366,768);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }

  public void actionPerformed(ActionEvent ae)
  {

    if(ae.getActionCommand().equals("Open"))
    {
      FileDialog fdial=new FileDialog(f,"Open Box",FileDialog.LOAD);
      fdial.setSize(300,300);
      fdial.setVisible(true);
      str=fdial.getDirectory();
      fl=new File(str);
      flist=fl.listFiles();
      b2.setEnabled(true);


      rat:while(j<flist.length)
      {
        if(flist[j].isFile())
        {
          if(flist[j].getName().toLowerCase().endsWith(".jpg"))
          {
            ig=new ImageIcon(fdial.getDirectory()+flist[j].getName());
            lab.setIcon(ig);
            break rat;

          }
        }

        j++;
      }


    }

    if(ae.getActionCommand().equals("<|"))
    {
      --j;

      if(j+1!=0)
      {
        bat:while(j<flist.length)
        {
          if(flist[j].isFile())
          {
            if(flist[j].getName().toLowerCase().endsWith(".jpg"))
            {
              ig=new ImageIcon(fdial.getDirectory()+flist[j].getName());
              lab.setIcon(ig);
              b1.setEnabled(true);
              break bat;
            }
          }

          j--;
        }
      }

      if(j<0 || !flist[j].isFile())
      {
        lab.setText("no image");
      }

      if(ae.getActionCommand().equals("|>"))
      {
        ++j;

        if(j-1!=flist.length)
        {
          cat:while(j<flist.length)
          {
            if(flist[j].isFile())
            {
              if(flist[j].getName().toLowerCase().endsWith(".jpg"))
              {
                ig=new ImageIcon(fdial.getDirectory()+flist[j].getName());
                lab.setIcon(ig);
                b1.setEnabled(true);
                break cat;

              }
            }

            j++;
          }
        }

        if(j>flist.length || !flist[j].isFile())
        {
          lab.setText("no image");
        }
      }

    }
  }
  public static void main(String args[])
  {
    new picframe();
  }


}

Answer 1

and that too unscaled

And what makes you think it should be otherwise?? Swing doesn't provide any components (of the top of my head) that do automatically scale its contents, this, you're going to have to work out for your self. Take a look at these previous questions on the subject for some solutions

• Java: maintaining aspect ratio of JPanel background image
• Jpanel resize on repaint

Updated #1

You other problems is this f.setLayout(null);, doing this means you suddenly become responsible for managing the size of components, so when you load a new image, it's size may be different from the previous, but you don't seem to make any attempt to update the image label...

Update #2

flist[j].getPath() will give you a better result then fdial.getDirectory()+flist[j].getName() as you may be missing the path separator ;)

Update #3

Here's a working example...without scaling

public class BetterBrowser {

    public static void main(String[] args) {
        new BetterBrowser();
    }

    public BetterBrowser() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new BrowserPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }

        });
    }

    public class BrowserPane extends JPanel {

        private FileModel fileModel;
        private JButton open;
        private JButton next;
        private JButton prev;

        private JLabel image;

        public BrowserPane() {
            fileModel = new FileModel();
            setLayout(new BorderLayout());

            JToolBar tb = new JToolBar();
            tb.add((open = new JButton(new OpenAction(fileModel))));

            add(tb, BorderLayout.NORTH);

            JPanel navPane = new JPanel(new FlowLayout(FlowLayout.CENTER));
            navPane.add((prev = new JButton(new PrevAction(fileModel))));
            navPane.add((next = new JButton(new NextAction(fileModel))));

            add(navPane, BorderLayout.SOUTH);
            add(new JScrollPane((image = new JLabel())));

            fileModel.addListDataListener(new ListDataListener() {
                @Override
                public void intervalAdded(ListDataEvent e) {
                }

                @Override
                public void intervalRemoved(ListDataEvent e) {
                }

                @Override
                public void contentsChanged(ListDataEvent e) {
                    if (e.getIndex0() == -1 && e.getIndex1() == -1) {
                        File file = (File) fileModel.getSelectedItem();
                        try {
                            ImageIcon icon = new ImageIcon(ImageIO.read(file));
                            image.setIcon(icon);
                        } catch (IOException exp) {
                            exp.printStackTrace();;
                            image.setIcon(null);
                        }
                    }
                }
            });
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 400);
        }

    }

    public class OpenAction extends AbstractAction {

        private FileModel model;

        public OpenAction(FileModel model) {
            this.model = model;
            putValue(NAME, "Open");
        }

        public FileModel getModel() {
            return model;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            JFileChooser fc = new JFileChooser();
            fc.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
            fc.setMultiSelectionEnabled(false);
            switch (fc.showOpenDialog((Component) e.getSource())) {
                case JFileChooser.APPROVE_OPTION:
                    File folder = fc.getSelectedFile();
                    File[] files = folder.listFiles(new FileFilter() {
                        @Override
                        public boolean accept(File pathname) {
                            String name = pathname.getName().toLowerCase();
                            return name.endsWith(".jpg")
                                            || name.endsWith(".png")
                                            || name.endsWith(".gif");
                        }

                    });

                    model.removeAllElements();

                    FileModel model = getModel();
                    for (File file : files) {
                        model.addElement(file);
                    }

                    if (model.getSize() > 0) {
                        model.setSelectedItem(model.getElementAt(0));
                    }
                    break;
            }
        }

    }

    public class FileModel extends DefaultComboBoxModel<File> {
    }

    public abstract class AbstractNavigationAction extends AbstractAction {

        private FileModel fileModel;
        private int direction;

        public AbstractNavigationAction(FileModel fileModel, int direction) {
            this.fileModel = fileModel;
            this.direction = direction;
            fileModel.addListDataListener(new ListDataListener() {
                @Override
                public void intervalAdded(ListDataEvent e) {
                    updateState();
                }

                @Override
                public void intervalRemoved(ListDataEvent e) {
                    updateState();
                }

                @Override
                public void contentsChanged(ListDataEvent e) {
                    updateState();
                }

            });
            updateState();
        }

        protected void updateState() {
            setEnabled(getFileModel().getSize() > 0);
        }

        public FileModel getFileModel() {
            return fileModel;
        }

        public int getDirection() {
            return direction;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            FileModel model = getFileModel();
            if (model.getSize() > 0) {
                File file = (File) model.getSelectedItem();
                int index = model.getIndexOf(file);

                index += direction;
                if (index < 0) {
                    index = model.getSize() - 1;
                } else if (index >= model.getSize()) {
                    index = 0;
                }
                file = model.getElementAt(index);
                model.setSelectedItem(file);
            }
        }

    }

    public class PrevAction extends AbstractNavigationAction {

        public PrevAction(FileModel fileModel) {
            super(fileModel, -1);
            putValue(NAME, "< Previous");
        }

    }

    public class NextAction extends AbstractNavigationAction {

        public NextAction(FileModel fileModel) {
            super(fileModel, 1);
            putValue(NAME, "Next >");
        }

    }

}

Answer 2

Mistakes are many mistakes I will help you to fix that mistakes.

First of all FileDialog fdial; sould be placed on the class attr. later reference it, but don't create a local variable.

Now the problem is in the actionPerformed method. First the equals method didn't worked because strings returned by the getActionCommand not correspond.

In the method actionPerformed you should switch between different cases and exit and nothing more.

The j variable used to keep current file in the list of files. Increase and decrease it should no exceed the bounds of the array or ArrayIndexOfBoundException.

The fixed code is:

public class picframe extends Thread implements ActionListener
{
  JTree tr;
  JScrollPane jsp;
  JFrame f;
  JButton b1,b2,b3;
  JLabel lab;
  File fl;
  File[] flist;
  ImageIcon ig;
  int k,j=0;
  FileDialog fdial;

  picframe ()
  {
    f=new JFrame("My Frame");
    f.setVisible(true);
    f.setLayout(null);


    lab=new JLabel();
    lab.setBounds(100,50,1166,500);
    f.add(lab);

    b1=new JButton(" <| ");
    b1.setBounds(486,600,100,30);
    b1.setEnabled(false);
    f.add(b1);
    b1.addActionListener(this);



    b2=new JButton(" |> ");
    b2.setBounds(786,600,100,30);
    f.add(b2);
    b2.setEnabled(false);
    b2.addActionListener(this);

    b3=new JButton("Open");
    b3.setBounds(633,650,100,30);
    f.add(b3);
    b3.addActionListener(this);

    f.pack();
    f.setSize(1366,768);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }

  public void actionPerformed(ActionEvent ae)
  {

    if(ae.getActionCommand().equals("Open"))
    {
      fdial=new FileDialog(f,"Open Box",FileDialog.LOAD);
      fdial.setSize(300,300);
      fdial.setVisible(true);
      String str=fdial.getDirectory();
      fl=new File(str);
      flist=fl.listFiles();
      b2.setEnabled(true);
      j = 0;
      if (flist != null)
        while(j<flist.length)
        {
          if(flist[j].isFile())
          {
            if(flist[j].getName().toLowerCase().endsWith(".jpg"))
            {
              ig=new ImageIcon(fdial.getDirectory()+flist[j].getName());
              lab.setIcon(ig);
              break;

            }
          }

          j++;
        }


    }

    if(ae.getActionCommand().equals(" <| "))
    {
      --j;
      if (flist != null)
        if(j<0 )  {
          j = -1;
          lab.setText("no image");
        } else {

          while(j<flist.length)
          {
            if(flist[j].isFile())
            {
              if(flist[j].getName().toLowerCase().endsWith(".jpg"))
              {
                ig=new ImageIcon(fdial.getDirectory()+flist[j].getName());
                lab.setIcon(ig);
                b1.setEnabled(true);
                break;
              }
            }

            j--;
          }
        }
    }

    if(ae.getActionCommand().equals(" |> "))
    {
      ++j;

      if (flist != null)
        if(j>=flist.length){
          j = flist.length;
          lab.setText("no image");
        } else  {
          while(j<flist.length)
          {
            if(flist[j].isFile())
            {
              if(flist[j].getName().toLowerCase().endsWith(".jpg"))
              {
                ig=new ImageIcon(fdial.getDirectory()+flist[j].getName());
                lab.setIcon(ig);
                b1.setEnabled(true);
                break;

              }
            }

            j++;
          }
        }
    }



  }
  public static void main(String args[])
  {
    new picframe ();
  }

}