CIS-257 Home: http://www.c-jump.com/bcc/c257c/c257syllabus.html

NetBeans GUI Builder, controls, and events

1. NetBeans GUI Project
2. Button Click Event
3. Swing containment hierarchy
4. Using JFrame class
5. JFrame default content pane
6. Using JPanel instead of the default content panel
7. Adding a menu bar to JFrame
8. The Root Pane
9. Classes in the Component hierarchy
10. java.awt.Container class
11. java.awt.Window class
12. javax.awt.JFrame class
13. Common properties for forms
14. JFrame Appearance
15. Common properties and methods for controls
16. Text Field Control
17. Displaying a form
18. JLabel control
19. JButton control
20. Runtime Events
21. ActionListener interface
22. Tool Tips
23. Font class
24. Extending the JFrame class

1. NetBeans GUI Project

• NetBeans, New Project

• Category: General Type: Java Application

• Make sure to deselect the "Create Main Class" checkbox

• For step-by-step instructions, see Setting up CelsiusConverter Project tutorial.

  • (This tutorial is part of Creating a GUI With JFC/Swing series of Oracle Java tutorials.)

   

2. Button Click Event

• Right-click the button in the design view and choose

  
      Events -> Action -> ActionPerformed
  
  

   

   

3. Swing containment hierarchy

• 
      javax.awt.JFrame
  
      javax.awt.JDialog
  
      javax.awt.JApplet
  
  

• Each of the above classes start a single containment hierarchy.

• AWT is the Abstract Window Toolkit, Java's original platform-independent windowing, graphics, and user-interface widget toolkit.

• The AWT is part of the Java Foundation Classes (JFC) - the standard Java GUI API.

   

4. Using JFrame class

• 
      // create JFrame
      JFrame firstFrame = new JFrame( "Hello" );
  
      // set size and title
      firstFrame.setSize( 200, 100 );
      firstFrame.setTitle( "My frame" );
  
  

   

5. JFrame default content pane

• Method

  
      frame.getContentPane() // returns a Container object
  
  

  returns the default content pane of the JFrame

• For example,

  
      frame.getContentPane().add( myLabel, BorderLayout.CENTER );
  
  

• The default content pane is a container that inherits from JComponent

• The pane is using the BorderLayout as its layout manager

• The default layout manager for JPanel is FlowLayout

   

6. Using JPanel instead of the default content panel

• 
  package pckg;
  
  import javax.swing.*;
  import javax.swing.event.*;
  import javax.swing.border.*;
  import javax.swing.text.*;
  import java.awt.BorderLayout;
  
  public class SwingMain
  {
      public static void main(String args [])
      {
          JFrame frame = new JFrame("JFrame is me");
          frame.setBounds(0, 0, 400, 300);
          frame.setDefaultCloseOperation( javax.swing.WindowConstants.EXIT_ON_CLOSE );
  
          // Create content JPanel
          JPanel contentPane = new JPanel( new BorderLayout() );
          Border border = BorderFactory.createEtchedBorder();
          border = BorderFactory.createTitledBorder( border, "My Title");
          contentPane.setBorder( border );
          frame.setContentPane( contentPane );
  
           // add button to layout:
          JButton button = new JButton( "Hello" );
          frame.getContentPane().add(button);
  
          frame.setVisible(true);
      } //main
  } //SwingMain
  
  

   

7. Adding a menu bar to JFrame

• 
      mbar = new JMenuBar();       // create menu bar
      frame.setJMenuBar( mbar );   // add to JFrame
  
  

   

8. The Root Pane

9. Classes in the Component hierarchy

• 
  import javax.swing.*;
  
      java.lang.Object
          java.awt.Component
              javax.awt.JComponent
  
      java.lang.Object
          java.awt.Component
              java.awt.Container	 
                  java.awt.Window
                      java.awt.Frame
                          javax.awt.JFrame
  
  

   

10. java.awt.Container class

• Type of component that holds other components

• Can treat group as single entity

• Defined in Container class

• Often takes form of window

  • Drag

  • Resize

  • Minimize

  • Restore

  • Close

   

11. java.awt.Window class

• Child of Container

• Does not have title bars or borders

• Rarely used

• Instead, use JFrame subclasses

   

12. javax.awt.JFrame class

• Swing GUI app:

  • creates JFrame

  • adds other GUI widgets within JFrame for display

• JFrame constructors:

  
  	JFrame()
  	JFrame( String title )
  	JFrame( GraphicsConfiguration gc )
  	JFrame( String title, GraphicsConfiguration gc )
  
  

   

13. Common properties for forms

• Default JFrame behavior:

  • When the user clicks Close button 'X', JFrame window becomes hidden, but the application keeps running.

• To allow window to close and exit the application,

  
      JFrame frame = new JFrame( "JFrame is me" );
      frame.setBounds( 0, 0, 400, 300 );
      frame.setDefaultCloseOperation( javax.swing.WindowConstants.EXIT_ON_CLOSE );
  
  

• To change the window title.

  
      frame.setTitle( "Celsius Converter App" );
  
  

• To make window fixed-size (non-resizable)

  
      frame.setResizable( false ); // default is true
  
  

   

14. JFrame Appearance

• Window decorations:

  • Icon and button Appearance

  • Look and feel

• Default appearance and behavior of user interface

  
      JFrame frame = new JFrame( "window caption goes here" );
      frame.setDefaultLookAndFeelDecorated( true );
  
  

   

15. Common properties and methods for controls

• 
      // Managing text
      getText()
      setText( String )
  
      // Enable text editing
      setEditable( boolean )        // whether user can edit the text
      selectAll()
  
      // Enable user interaction with the control
      setEnabled( boolean )         // if enabled, it may respond to user input
  
      // Enable control to receive focus on the form
      requestFocusInWindow()        // set focus
      setFocusable( boolean )       // enable to receive focus
  
      // Set horizontal alignment for the text
      // JTextField.LEFT, CENTER, RIGHT, LEADING, TRAILING
      setHorizontalAlignment( int )
      getHorizontalAlignment()
  
  

   

16. Text Field Control

• JTextField is a component where user can type a single line of text data

• Getting text from the control:

  
      double dbl = Double.parseDouble( myTextField.getText() );
      int value = Integer.parseInt( myTextField.getText() );
  
  

• Setting the text in a control:

  
      myTextField.setText( "HELLO" );
  
  

• Moving focus to the control:

  
      myTextField.requestFocusInWindow();
  
  

   

17. Displaying a form

• Two methods for displaying a form:

  
      frame.setVisible( boolean ) // makes window visible (the default is invisible)
  
      setLocationRelativeTo( component ) // set the location of dialog in respect of parent dialog
      setLocationRelativeTo( null )  // centers the window on the screen
  
  

   

18. JLabel control

• Holds visible text on the form

• Methods:

  
      add()
      remove()
      setText()
      getText()
  
  

   

19. JButton control

• Represents a clickable button

• Methods:

  
      setText( String caption )
      getText() // get caption
  
  

• JFrame.add() method adds JButton to the frame

• Note: when clicked, no resulting action occurs -- the code has to be written to handle the click event.

   

20. Runtime Events

• Event-driven program expects various events in any order: user keystrokes, mouse clicks, minimizing windows, and so on

• Source: a component where the event is generated

• Listener: an object to be notified about the event and processing it

• To accept event messages, create a class that implements ActionListener:

  
      import java.awt.*;
      import java.awt.event.*;
      import javax.swing.*;
      import javax.swing.event.*;
  
      class MyButtonClickAction implements ActionListener
      {
          JButton mButton;
  
          public MyButtonClickAction( JButton button )
          {
              mButton = button;
          }
  
          /** 
          * Handles user clicks
          */
          public void actionPerformed( ActionEvent event )
          {
              mButton.setText( "Click!" );
          }
      }//class MyButtonClickAction
  
  

• Add action listener to the event source widget:

  
      JButton button = new JButton( "Hello" );
      button.addActionListener( new MyButtonClickAction( button ) );
  
  

   

21. ActionListener interface

• ActionListener interface specifies the

  
      actionPerformed( ActionEvent evt );
  
  

  method. The implementation can execute any statements in response to the event.

• The actionPerformed() is invoked when the user

  • clicks a button

  • chooses a menu item

• Note: When more than one component is added to the JFrame, it is necessary to find out which component is the source of the event:

  
      /** 
      * Handles user clicks
      */
      public void actionPerformed( ActionEvent event )
      {
          Object obj = event.getSource();
          if ( obj == mButton )
          {
              mButton.setText( "Click!" );
          }
      }
  
  

   

22. Tool Tips

• A tool tip helps to understand the purpose of component on the input form

• Tool tips appear when a user hovers the mouse over the component

  
      // Create frame
      // ...
      // Add button and set font:
      JButton button = new JButton( "Hello" );
      button.setToolTipText( "tool tip text goes here" );
      frame.getContentPane().add( button );
      frame.setVisible( true );
  
  

   

23. Font class

• Creates an object that holds typeface and size information

• Font constructor arguments: typeface, style, and point size.

• For example, changing a JButton's font requires Font object argument:

  
      // Create frame
      // ...
      // Add button and set font:
      JButton button = new JButton( "Hello" );
      Font headlineFont = new Font( "Arial", Font.BOLD, 36 );
      button.setFont( headlineFont );
      frame.getContentPane().add( button );
      frame.setVisible( true );
  
  

   

24. Extending the JFrame class

• Common practice: define a class that descends from JFrame class

• Advantages: configure JFrame properties and controls in object's constructor

• Note: remember to call parent class constructor using the super keyword

  
      public class JMyFrame extends JFrame
      {
          static final int WINDOW_WIDTH = 210;
          static final int WINDOW_HEIGHT = 130;
  
          //constructor
          public JMyFrame()
          {
              super( "window title goes here" );
              setSize( WINDOW_WIDTH, WINDOW_HEIGHT );
              setDefaultCloseOperation( javax.swing.WindowConstants.EXIT_ON_CLOSE );
              setVisible( true );
          }
      }//class JMyFrame