< Back >

• Instructions for making interfaces   
   
• Chapter ‘Creating a GUI with JFC/Swing’ in Java Tutorial explains how to create interfaces, but here is short ‘conclusion’ for it:

  Appearences of forms
   

  • To have own LayoutManager for each of the windows, that is the idea of making forms.
    These managers then handle the locations of interface elements on the form.
    
  • There are numerous LayoutManager methods to choose from.
    This is an example of one of the most complex and versatile LayoutManager that exits : GridBagLayout.

public class PasswordWindow extends JFrame {

....

Container pane = getContentPane();
pane.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
c.anchor = GridBagConstraints.WEST;
// Anchors elements to ‘west’ (left),

c.fill = GridBagConstraints.HORIZONTAL;
// If component has more space to use than needed,
// width will be increased horizontally.

c.insets = new Insets(2,2,2,2);
// 2 pixels of space is left around each element.
c.gridx = 0;
c.gridy = 0;

jlYritys = new JLabel("Company:");
pane.add(jlCompany,c);
c.gridy++;

jtfCompany = new JTextField(14);
pane.add(jtfCompany,c);
c.gridy++;

etc.

c.gridx = 0;
c.gridwidth = GridBagConstraints.REMAINDER;
// If some elements needs more cells horizontally,
// GRIDWIDTH value can be set to meet cell count needed
// or just use the line above, which takes rest of the row.
jlLAFLabel = new JLabel("Available Look And Feels:");
pane.add(jlLAFLabel, c);

etc.

• Using JPanel component in proper place, you can put one LM within the other.
  JPanel is invisible to user and it is inherited from Container,
  so it can have own LM and it accepts also .add commands.

< Top >

Form functions

• When improving functionality of an interface, the idea is to set own ‘listning’ classes for each of the components,
  which can then call methods when certain events happen. Events that need such methods are:
   
  • Moving the mouse
  • Clicking a button (on form)
  • Moving focus on/off a field
  • Pushing button (on keyboard)
  • Opening/closing window
  • Etc.
     
• These ‘listeners’ can be set using 3 different ways:

  Option 1 : create own interface
   

  • Interface class of its own can do the job:
    

  public class SendWindow extends JFrame implements ActionListener {
  
      ....

      JButton jb = new JButton("Send");
      jb.addActionListener( this );
      jb.setActionCommand("Send");
      pane.add( jb, c );

  ....

  public void actionPerformed( ActionEvent e) {
      if (e.getActionCommand().equals("Send")) {
  
    ...
  
    }
  }
   

  < Top >

  Option 2 : create own class
   

  • Listener can be also a class of its own:

  .....

  jtfField.addFocusListener( new LookupListener( jtfField, this, ... ) );
  
  .....

  public class LookupListener implements FocusListener {
  public LookupListener( JTextField p_jtfField, JFrame p_jframe, ... ) {

  ...

  }

  // ---------------- f o c u s G a i n e d --------------
  /**
  * Save old value
  */
  // bTemporary == true if cursor moves outside of the windows
  public void focusGained( FocusEvent e) {
      if (!bTemporary) {

      ....

    }
  }

  // -------------------- f o c u s L o s t --------------------
  /**
  * Will be executed when focus is lost. Check lookup status.
  * If lookup was not found method for that case will be executed
  */
  public void focusLost( FocusEvent e) {
      if (e.isTemporary())
          bTemporary = true;
      else {
          bTemporary = false;

      ......

      }
    }
  }

  < Top >

  Option 3 : create a minor class
   

  Listener can set as a minor class which is inherited from major class and is executed immediately after major class.
  Although this custom is quite rapid, wide use of it can cause quite messy code.
  This method is best used when only a few events are handled.

  ....

  setTitle( "Title" );
  addWindowListener( new WindowAdapter() {
      public void windowActivated( WindowEvent e) {
          System.out.println("windowActivated");

      }

      public void windowDeactivated( WindowEvent e) {
          System.out.println("windowDeactivated");
      }
  
      public void windowOpened( WindowEvent e) {
          System.out.println("windowOpened");   
      }

      public void windowClosing( WindowEvent e) {
          System.out.println("windowClosing");
      }

      public void windowClosed( WindowEvent e) {
          System.out.println("windowClosing");
      }
  });

  JPanel jpParameters = new JPanel( new GridBagLayout() );
  GridBagConstraints c = new GridBagConstraints();
  c.gridx = 0;  c.gridy = 0;
  c.anchor = GridBagConstraints.WEST;

  .....

  Code above is kind of a ‘short expression’ in which a new class is specified.
  This class is inherited from class WindowAdapter and it also get new instance at the same time.

    <Top>

< Back >