How to "hide" a JFrame using a JButton outside the main

Question

So i've nearly completed this project, the last thing being the "hide" button. My teacher never gave instruction on what to do, but since it's annoying me and I can't find an answer that works, I figured i'd ask you good folks.

I've tried:

1. setExtendedState(JFrame.ICONIFIED) //causes a compiler error, can't find my variable name
2. setState(JFrame.ICONIFIED) //same issue, "can't find symbol", or rather find my variable
3. setVisible(false) //this doesn't work bc it hides my entire frame, and I can't get it back without closing the program.

I use Container c = getContentPane() to create the pane, then inside the main I use:

ClassName variableName = new ClassName() to create the parameters.

This is how I was taught and I have to use this way for now(since it is what my teacher wants) but I have noticed there are other ways to achieve this same goal.

Any input specific to my program would be awesome! Thanks!

My program as follows(I posted the whole thing so nothing may be left out):

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Arrays;

public class Project9 extends JFrame
{
  Font f1 = new Font("Serif", Font.BOLD, 30);
  Font f2 = new Font("Serif", Font.PLAIN, 18);

  private BOOKItem[] bookArray = new BOOKItem[10];

  private JLabel headerLbl;
  private JLabel messagesLbl;

  private JTextField idLabelFld;
  private JTextField idFld;
  private JTextField priceLabelFld;
  private JTextField priceFld;
  private JTextField numInStockLabelFld;
  private JTextField numInStockFld;
  private JTextField codeLabelFld;
  private JTextField codeFld;
  private JTextField messagesFld;

  private JButton insertBtn;
  private JButton deleteBtn;
  private JButton displayBtn;
  private JButton displayOneBtn;
  private JButton hideBtn;
  private JButton clearBtn;

  private String input = "";
  private String displayOneStr = "";

  private int idInput = 0;
  private double priceInput = 0.0;
  private int numInStockInput = 0;
  private int codeInput = 0;

  private int index = 0;
  private int numItems = 0;
  private int responseCode = 0;

  private Container c = getContentPane();

  //Main Method, sets arrayFrame params
  public static void main(String[] args)
  {
        Project9 arrayFrame = new Project9();
        arrayFrame.setSize(555,450);
        arrayFrame.setVisible(true);
        arrayFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }     


  //Constructor
  public Project9()
  {
        //Creates the array 
        for (int i = 0; i < bookArray.length; i++)
        {
              bookArray[i] = new BOOKItem();
              System.out.println(bookArray[i]);
        } 

        setTitle("Project 9");
        c.setLayout(new FlowLayout());

        headerLbl = new JLabel("Data Entry: BestBargainBook Store");
        headerLbl.setFont(f1);
        c.add(headerLbl);

        idLabelFld = new JTextField("Enter ID:", 15);
        idLabelFld.setEditable(false);
        c.add(idLabelFld);

        idFld = new JTextField(25);
        c.add(idFld);

        priceLabelFld = new JTextField("Enter Price:", 15);
        priceLabelFld.setEditable(false);
        c.add(priceLabelFld);

        priceFld = new JTextField(25);
        c.add(priceFld);

        numInStockLabelFld = new JTextField("Enter Number In Stock:", 15);
        numInStockLabelFld.setEditable(false);
        c.add(numInStockLabelFld);

        numInStockFld = new JTextField(25);
        c.add(numInStockFld);

        codeLabelFld = new JTextField("Enter Code: 1,2,3 or 4:", 15);
        codeLabelFld.setEditable(false);
        c.add(codeLabelFld);

        codeFld = new JTextField(25);
        c.add(codeFld);

        insertBtn = new JButton("Insert");
        c.add(insertBtn);

        deleteBtn = new JButton("Delete");
        c.add(deleteBtn);

        displayBtn = new JButton("Display");
        c.add(displayBtn);

        displayOneBtn = new JButton("DisplayOne");
        c.add(displayOneBtn);

        hideBtn = new JButton("Hide");
        c.add(hideBtn);

        clearBtn = new JButton("Clear");
        c.add(clearBtn);

        messagesLbl = new JLabel("Messages:");
        messagesLbl.setFont(f2);
        c.add(messagesLbl);

        messagesFld = new JTextField(30);
        c.add(messagesFld);

        //Event Listeners
        insertBtn.addActionListener(new EventHandler());
        deleteBtn.addActionListener(new EventHandler());
        displayBtn.addActionListener(new EventHandler());
        displayOneBtn.addActionListener(new EventHandler());
        hideBtn.addActionListener(new EventHandler());
        clearBtn.addActionListener(new EventHandler());

  }//end constructor      

private class EventHandler implements ActionListener
{
  public void actionPerformed(ActionEvent ev)
  {

        if (ev.getSource() == insertBtn)
        {
              input = idFld.getText();
              idInput = Integer.parseInt(input);

              input = priceFld.getText();
              priceInput = Double.parseDouble(input);

              input = numInStockFld.getText();
              numInStockInput = Integer.parseInt(input);

              input = codeFld.getText();
              codeInput = Integer.parseInt(input);

              insert(idInput, priceInput, numInStockInput, 
                     codeInput); 

              if (responseCode == 0)
              {
                    messagesFld.setText("Array is full. Cannot insert book ID: " + 
                                        idInput);
              }
              else if (responseCode == 1)
              {
                    messagesFld.setText("Succesful insertion of " + idInput);
              }
              else if (responseCode == -1)
              {
                    messagesFld.setText("Duplicate ID: " + idInput);
              }                          



        }

        else if (ev.getSource() == deleteBtn)
        {
              input = idFld.getText();
              idInput = Integer.parseInt(input);

              delete(idInput);

              if (responseCode == 1)
              {      
                    messagesFld.setText("Successful delete of book ID: " +
                                        idInput);
              }
              else if (responseCode == -1)
              {
                    messagesFld.setText("ID: " + idInput + " not found.");
              }                                

        }

        else if (ev.getSource() == displayBtn)
        {
              for (index = 0; index < bookArray.length; index++)
              {
                    bookArray[index].display();
              }      
        }

        else if (ev.getSource() == displayOneBtn)
        {
              input = idFld.getText();
              idInput = Integer.parseInt(input);

              for (index = 0; index < bookArray.length; index++)
              {
                    if (bookArray[index].getID() == idInput)
                    {
                          bookArray[index].getID();
                          bookArray[index].getPrice();
                          bookArray[index].getNumberInStock();
                          bookArray[index].getCode();

                          messagesFld.setText("id: " + bookArray[index].getID() +
                                              "  Price: " + bookArray[index].getPrice() +
                                              "  Number In Stock: " + bookArray[index].getNumberInStock() +
                                              "  Code: " + bookArray[index].getCode()); 
                    }
              }      

        }      

        else if (ev.getSource() == hideBtn)
        {

        }

        else if (ev.getSource() == clearBtn)
        {
              idFld.setText("");
              priceFld.setText("");
              numInStockFld.setText("");
              codeFld.setText("");
              messagesFld.setText("");
              repaint();
        }

  }//End actionPerformed

}//End handler

  //insert method, called when insert button is pressed
  public int insert(int iD, double prc, int numInStock, int code)
  {
        if (numItems == 10)
        {
              System.out.println("\nThe Array is full, please delete an entry");

              responseCode = 0;
              return responseCode;
        }      

        for (index = 0; index < bookArray.length; index++)
        {
              if (bookArray[index].getID() == iD)
              {
                    System.out.println("\nThat ID already exists");

                    responseCode = -1;
                    return responseCode;
              }
              else if (bookArray[index].getID() == 0)
              {
                    bookArray[index] = new BOOKItem(iD, prc, numInStock, code);
                    numItems++; 

                    System.out.println("\n" + idInput + "\n" + priceInput + "\n" + 
                                       numInStockInput + "\n" + codeInput + "\n" + index);
                    System.out.println("\nID: " + bookArray[index].getID());
                    System.out.println("Price: " + bookArray[index].getPrice());
                    System.out.println("NIS: " + bookArray[index].getNumberInStock());
                    System.out.println("Code: " + bookArray[index].getCode());
                    System.out.println("Items in Array: " + numItems); 

                    responseCode = 1;
                    return responseCode;
              }               

        }

        return responseCode;

  }//end insert method 

  //Delete method, called when delete button is pressed
  public int delete(int id)
  {
        for (index = 0; index < bookArray.length; index++)
        {
              if (bookArray[index].getID() == id)
              {
                    bookArray[index].setID(0);
                    bookArray[index].setPrice(0);
                    bookArray[index].setStock(0);
                    bookArray[index].setCode(0);
                    numItems--;
                    System.out.println("\nSuccessful deletion");

                    responseCode = 1;
                    return responseCode;
              }               

        }

        responseCode = -1;
        return responseCode;

  }//end delete method


}//end app                                                                 

Answer 1

In the ActionListener for your "Hide" button the basic code would be:

JButton button = (JButton)e.getSource();
Window window = SwingUtilities.windowForComponent( button );
JFrame frame = (JFrame)window;
frame.setState(JFrame.ICONIFIED);

This way you are not depending on any instance variable that identifies your frame. Using the source object of the event is a good way to make your listeners generic and flexible.

Answer 2

You can just simply do this with a button listener that sets the visiblity of the frame to false:

button.addActionListener(new ActionListener()
{
    public void actionPerformed(ActionEvent e)
    {
        frame.setVisible(false);
    }
});

If you want to iconify a JFrame:

minimize with frame.setState(Frame.ICONIFIED)

restore with frame.setState(Frame.NORMAL)

taken from: How to minimize a JFrame window from Java?

Answer 3

In your EventHandler nested class, try something like

Project9.this.setState(JFrame.ICONIFIED);