32.5. PreparedStatement | Introduction to Java Programming-Comprehensive Version (6th Edition)

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29.7. Creating Custom Dialogs

Standard JOptionPane dialogs are sufficient in most cases. Occasionally, you need to create custom dialogs. In Swing, the JDialog class can be extended to create custom dialogs.

As with JFrame , components are added to the contentPane of JDialog . Creating a custom dialog usually involves laying out user interface components in the dialog, adding buttons for dismissing the dialog, and installing listeners that respond to button actions.

The standard dialog is modal , which means that no other window can be accessed before the dialog is dismissed. However, the custom dialogs derived from JDialog are not modal by default. To make a dialog modal, set its modal property to true . To display an instance of JDialog , set its visible property to true .

Let us create a custom dialog box for choosing colors, as shown in Figure 29.17(a). Use this dialog to choose the color for the foreground of the button, as shown in Figure 29.17(b). When the user clicks the Change Button Text Color button, the Choose Color dialog box is displayed.

Figure 29.17. The custom dialog allows you to choose a color for the label's foreground.

Create a custom dialog component named ColorDialog by extending JDialog . Use three sliders to specify red, green, and blue components of a color. The program is given in Listing 29.6.

Listing 29.6. ColorDialog.java

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 1   import   java.awt.*; 2   import   java.awt.event.*; 3   import   javax.swing.*; 4   import   javax.swing.event.*; 5 6   public      class   ColorDialog   extends   JDialog  { 7  // Declare color component values and selected color  8   private int   redValue, greenValue, blueValue; 9   private   Color color =   null   ; 10 11  // Create sliders  12   private   JSlider jslRed =   new   JSlider(     ,   128   ); 13   private   JSlider jslGreen =   new   JSlider(     ,   128   ); 14   private   JSlider jslBlue =   new   JSlider(     ,   128   ); 15 16  // Create two buttons  17   private   JButton jbtOK =   new   JButton(   "OK"   ); 18   private   JButton jbtCancel =   new   JButton(   "Cancel"   ); 19 20  // Create a panel to display the selected color  21   private   JPanel jpSelectedColor =   new   JPanel(); 22

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 23    public   ColorDialog()  { 24    this   (   null   ,   true   );  25 } 26 27    public   ColorDialog(java.awt.Frame parent,   boolean   modal)  { 28    super   (parent, modal);  29 setTitle(   "Choose Color"   ); 30 31  // Group two buttons OK and Cancel  32 JPanel jpButtons =   new   JPanel(); 33 jpButtons.add(jbtOK); 34 jpButtons.add(jbtCancel); 35 36  // Group labels  37 JPanel jpLabels =   new   JPanel(); 38 jpLabels.setLayout(   new   GridLayout(   3   ,     )); 39 jpLabels.add(   new   JLabel(   "Red"   )); 40 jpLabels.add(   new   JLabel(   "Green"   )); 41 jpLabels.add(   new   JLabel(   "Blue"   )); 42 43  // Group sliders for selecting red, green, and blue colors  44 JPanel jpSliders =   new   JPanel(); 45 jpSliders.setLayout(   new   GridLayout(   3   ,     )); 46 jpSliders.add(jslRed); 47 jpSliders.add(jslGreen); 48 jpSliders.add(jslBlue); 49 50  // Group jpLabels and jpSliders  51 JPanel jpSelectColor =   new   JPanel(); 52 jpSelectColor.setLayout(   new   BorderLayout()); 53 jpSelectColor.setBorder( 54 BorderFactory.createTitledBorder(   "Select Color"   )); 55 jpSelectColor.add(jpLabels, BorderLayout.WEST); 56 jpSelectColor.add(jpSliders, BorderLayout.CENTER); 57 58  // Group jpSelectColor and jpSelectedColor  59 JPanel jpColor =   new   JPanel(); 60 jpColor.setLayout(   new   BorderLayout()); 61 jpColor.add(jpSelectColor, BorderLayout.SOUTH); 62 jpColor.add(jpSelectedColor, BorderLayout.CENTER); 63 64  // Place jpButtons and jpColor into the dialog box  65 add(jpButtons, BorderLayout.SOUTH); 66 add(jpColor, BorderLayout.CENTER); 67 pack(); 68 69  jbtOK.addActionListener(   new   ActionListener()  { 70    public void   actionPerformed(ActionEvent e)  { 71  setVisible(   false   );  72 } 73 }); 74 75  jbtCancel.addActionListener(   new   ActionListener()  { 76    public void   actionPerformed(ActionEvent e)  { 77  color =   null   ;  78  setVisible(   false   );  79 } 80 }); 81

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 82 jslRed.addChangeListener(   new   ChangeListener() { 83   public void   stateChanged(ChangeEvent e) { 84 redValue = jslRed.getValue(); 85 color =   new   Color(redValue, greenValue, blueValue); 86 jpSelectedColor.setBackground(color); 87 } 88 }); 89 90 jslGreen.addChangeListener(   new   ChangeListener() { 91   public void   stateChanged(ChangeEvent e) { 92 greenValue = jslGreen.getValue(); 93 color =   new   Color(redValue, greenValue, blueValue); 94 jpSelectedColor.setBackground(color); 95 } 96 }); 97 98 jslBlue.addChangeListener(   new   ChangeListener() { 99   public void   stateChanged(ChangeEvent e) { 100 blueValue = jslBlue.getValue(); 101 color =   new   Color(redValue, greenValue, blueValue); 102 jpSelectedColor.setBackground(color); 103 } 104 }); 105 } 106 107   public   Dimension getPreferredSize() { 108   return new   java.awt.Dimension(   200   ,   200   ); 109 } 110 111  /** Return color */  112   public   Color getColor() { 113   return   color; 114 } 115 }

Create a test class to use the color dialog to select the color for the foreground color of the button in Listing 29.7.

Listing 29.7. TestColorDialog.java

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 1   import   javax.swing.*; 2   import   java.awt.*; 3   import   java.awt.event.*; 4 5   public class   TestColorDialog   extends   JApplet { 6   private   ColorDialog colorDialog1 =   new   ColorDialog(); 7   private   JButton jbtChangeColor =   new   JButton(   "Choose color"   ); 8 9   public   TestColorDialog() { 10 setLayout(   new   java.awt.FlowLayout()); 11 jbtChangeColor.setText(   "Change Button Text Color"   ); 12 jbtChangeColor.addActionListener(   new   ActionListener() { 13   public void   actionPerformed(ActionEvent e) { 14 colorDialog1.setVisible(   true   ); 15 16   if   (colorDialog1.getColor() !=   null   ) 17 jbtChangeColor.setForeground(colorDialog1.getColor()); 18 } 19 });

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 20 add(jbtChangeColor); 21 } 22 }

The custom dialog box allows the user to use the sliders to select colors. The selected color is stored in the color variable. When the user clicks the Cancel button, color becomes null , which implies that no selection has been made.

The dialog box is displayed when the user clicks the "Change Button Text Color" button and is closed when the OK button or the Cancel button is clicked.

Tip

Not setting the dialog modal when needed is a common mistake. In this example, the dialog is set modal in line 24 in ColorDialog.java (Listing 29.6). If the dialog is not modal, all the statements in the "Change Button Text Color" button handler are executed before the color is selected from the dialog box.