Core Java™ 2 Volume II - Advanced Features, Seventh

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• Core Java™ 2 Volume II - Advanced Features, Seventh Edition

• By: Cay S. Horstmann; Gary Cornell

• Publisher: Prentice Hall

• Pub. Date: November 22, 2004   Most Recent Edition

• Print ISBN-10: 0-13-111826-9

• Print ISBN-13: 978-0-13-111826-3

• Pages in Print Edition: 1024

• Subscriber Rating: [0 Ratings]

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关键词：features Advanced Seventh ADVANCE feature Java

1. Code View: Scroll / Show All
   
2. 1. package com.horstmann.corejava;
   
3. 2.
   
4. 3. import java.awt.*;
   
5. 4. import java.io.*;
   
6. 5. import javax.imageio.*;
   
7. 6. import javax.swing.*;
   
8. 7.
   
9. 8. /**
   
10. 9.    A bean for viewing an image.
    
11. 10. */
    
12. 11. public class ImageViewerBean extends JLabel
    
13. 12. {
    
14. 13.
    
15. 14.    public ImageViewerBean()
    
16. 15.    {
    
17. 16.       setBorder(BorderFactory.createEtchedBorder());
    
18. 17.    }
    
19. 18.
    
20. 19.    /**
    
21. 20.       Sets the fileName property.
    
22. 21.       @param fileName the image file name
    
23. 22.    */
    
24. 23.    public void setFileName(String fileName)
    
25. 24.    {
    
26. 25.       try
    
27. 26.       {
    
28. 27.          file = new File(fileName);
    
29. 28.          setIcon(new ImageIcon(ImageIO.read(file)));
    
30. 29.       }
    
31. 30.       catch (IOException e)
    
32. 31.       {
    
33. 32.          file = null;
    
34. 33.          setIcon(null);
    
35. 34.       }
    
36. 35.    }
    
37. 36.
    
38. 37.    /**
    
39. 38.       Gets the fileName property.
    
40. 39.       @return the image file name
    
41. 40.    */
    
42. 41.    public String getFileName()
    
43. 42.    {
    
44. 43.       if (file == null) return null;
    
45. 44.       else return file.getPath();
    
46. 45.    }
    
47. 46.
    
48. 47.    public Dimension getPreferredSize()
    
49. 48.    {
    
50. 49.       return new Dimension(XPREFSIZE, YPREFSIZE);
    
51. 50.    }
    
52. 51.
    
53. 52.    private File file = null;
    
54. 53.    private static final int XPREFSIZE = 200;
    
55. 54.    private static final int YPREFSIZE = 200;
    
56. 55. }
    
57. 
    
58. 
    
59.                                           

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Simple Properties

A simple property is one that takes a single value such as a string or a number. The fileName property of the ImageViewer is an example of a simple property. Simple properties are easy to program: Just use the set/get naming convention we indicated earlier. For example, if you look at the code in Example 8-1, you can see that all it took to implement a simple string property is the following:

[size=28.3500003814697px]

1. public void setFileName(String f)
   
2. {
   
3.    fileName = f;
   
4.    image = . . .
   
5.    repaint();
   
6. }
   
7. 
   
8. public String getFileName()
   
9. {
   
10.    if (file == null) return null;
    
11.    else return file.getPath();
    
12. }

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Indexed Properties

An indexed property is one that gets or sets an array. A chart bean (see below) would use an indexed property for the data points. With an indexed property, you supply two pairs of get and set methods: one for the array and one for individual entries. They must follow this pattern:

Type[] getPropertyName()
void setPropertyName(Type[] x)
Type getPropertyName(int i)
void setPropertyName(int i, Type x)

Here's an example of the indexed property we use in the chart bean that you will see later in this chapter.

1. public double[] getValues() { return values; }
   
2. public void setValues(double[] v) { values = v; }
   
3. public double getValues(int i)
   
4. {
   
5.    if (0 <= i && i < values.length) return values[i];
   
6.    return 0;
   
7. }
   
8. public void setValues(int i, double value)
   
9. {
   
10.    if (0 <= i && i < values.length) values[i] = value;
    
11. }
    
12. . . .
    
13. private double[] values;

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The

setPropertyName(int i, Type x)

method cannot be used to grow the array. To grow the array, you must manually build a new array and then pass it to this method:

Constrained Properties

[size=28.3500003814697px]A constrained property is constrained by the fact that any listener can “veto” proposed changes, forcing it to revert to the old setting. The Java library contains only a few examples of constrained properties. One of them is the closed property of the JInternalFrame class. If someone tries to callsetClosed(true) on an internal frame, then all of its VetoableChangeListeners are notified. If any of them throws a PropertyVetoException, then the closed property is not changed, and the setClosedmethod throws the same exception. For example, a VetoableChangeListener may veto closing the frame if its contents have not been saved.

[size=28.3500003814697px]To build a constrained property, your bean must have the following two methods to manageVetoableChangeListener objects:

[size=28.3500003814697px]public void addVetoableChangeListener(VetoableChangeListener listener);public void removeVetoableChangeListener(VetoableChangeListener listener);

[size=28.3500003814697px]Just as there is a convenience class to manage property change listeners, there is a convenience class, called VetoableChangeSupport, that manages vetoable change listeners. Your bean should contain an object of this class.

[size=28.3500003814697px]
private VetoableChangeSupport vetoSupport = new VetoableChangeSupport(this);

[size=28.3500003814697px]Adding and removing listeners should be delegated to this object. For example:

[size=28.3500003814697px]

1. public void addVetoableChangeListener(VetoableChangeListener listener)
   
2. {
   
3.    vetoSupport.addVetoableChangeListener(listener);
   
4. }
   
5. public void removeVetoableChangeListener(VetoableChangeListener listener)
   
6. {
   
7.    vetoSupport.removeVetoableChangeListener(listener);
   
8. }

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1. 1. package com.horstmann.corejava;
   
2.   2.
   
3.   3. import java.awt.*;
   
4.   4. import java.awt.event.*;
   
5.   5. import java.beans.*;
   
6.   6. import java.io.*;
   
7.   7. import javax.swing.*;
   
8.   8.
   
9.   9. /**
   
10. 10.    A bean for specifying file names.
    
11. 11. */
    
12. 12. public class FileNameBean extends JPanel
    
13. 13. {
    
14. 14.    public FileNameBean()
    
15. 15.    {
    
16. 16.       dialogButton = new JButton("...");
    
17. 17.       nameField = new JTextField(30);
    
18. 18.
    
19. 19.       chooser = new JFileChooser();
    
20. 20.
    
21. 21.       chooser.setFileFilter(new
    
22. 22.          javax.swing.filechooser.FileFilter()
    
23. 23.          {
    
24. 24.             public boolean accept(File f)
    
25. 25.             {
    
26. 26.                String name = f.getName().toLowerCase();
    
27. 27.                return name.endsWith("." + defaultExtension) || f.isDirectory();
    
28. 28.             }
    
29. 29.             public String getDescription()
    
30. 30.             {
    
31. 31.                return defaultExtension + " files";
    
32. 32.             }
    
33. 33.          });
    
34. 34.
    
35. 35.       setLayout(new GridBagLayout());
    
36. 36.       GridBagConstraints gbc = new GridBagConstraints();
    
37. 37.       gbc.weightx = 100;
    
38. 38.       gbc.weighty = 100;
    
39. 39.       gbc.anchor = GridBagConstraints.WEST;
    
40. 40.       gbc.fill = GridBagConstraints.BOTH;
    
41. 41.       gbc.gridwidth = 1;
    
42. 42.       gbc.gridheight = 1;
    
43. 43.       add(nameField, gbc);
    
44. 44.
    
45. 45.       dialogButton.addActionListener(
    
46. 46.          new ActionListener()
    
47. 47.          {
    
48. 48.             public void actionPerformed(ActionEvent event)
    
49. 49.             {
    
50. 50.                int r = chooser.showOpenDialog(null);
    
51. 51.                if(r == JFileChooser.APPROVE_OPTION)
    
52. 52.                {
    
53. 53.                   File f = chooser.getSelectedFile();
    
54. 54.                   try
    
55. 55.                   {
    
56. 56.                      String name = f.getCanonicalPath();
    
57. 57.                      setFileName(name);
    
58. 58.                   }
    
59. 59.                   catch (IOException e)
    
60. 60.                   {
    
61. 61.                   }
    
62. 62.                }
    
63. 63.             }
    
64. 64.          });
    
65. 65.       nameField.setEditable(false);
    
66. 66.
    
67. 67.       gbc.weightx = 0;
    
68. 68.       gbc.anchor = GridBagConstraints.EAST;
    
69. 69.       gbc.fill = GridBagConstraints.NONE;
    
70. 70.       gbc.gridx = 1;
    
71. 71.       add(dialogButton, gbc);
    
72. 72.    }
    
73. 73.
    
74. 74.    /**
    
75. 75.       Sets the fileName property.
    
76. 76.       @param newValue the new file name
    
77. 77.    */
    
78. 78.    public void setFileName(String newValue)
    
79. 79.    {
    
80. 80.       String oldValue = nameField.getText();
    
81. 81.       nameField.setText(newValue);
    
82. 82.       firePropertyChange("fileName", oldValue, newValue);
    
83. 83.    }
    
84. 84.
    
85. 85.    /**
    
86. 86.       Gets the fileName property.
    
87. 87.       @return the name of the selected file
    
88. 88.    */
    
89. 89.    public String getFileName()
    
90. 90.    {
    
91. 91.       return nameField.getText();
    
92. 92.    }
    
93. 93.
    
94. 94.    /**
    
95. 95.       Sets the defaultExtension property.
    
96. 96.       @param s the new default extension
    
97. 97.    */
    
98. 98.    public void setDefaultExtension(String s)
    
99. 99.    {
    
100. 100.       defaultExtension = s;
     
101. 101.    }
     
102. 102.
     
103. 103.    /**
     
104. 104.       Gets the defaultExtension property.
     
105. 105.       @return the default extension in the file chooser
     
106. 106.    */
     
107. 107.    public String getDefaultExtension()
     
108. 108.    {
     
109. 109.       return defaultExtension;
     
110. 110.    }
     
111. 111.
     
112. 112.    public Dimension getPreferredSize()
     
113. 113.    {
     
114. 114.       return new Dimension(XPREFSIZE, YPREFSIZE);
     
115. 115.    }
     
116. 116.
     
117. 117.    private static final int XPREFSIZE = 200;
     
118. 118.    private static final int YPREFSIZE = 20;
     
119. 119.    private JButton dialogButton;
     
120. 120.    private JTextField nameField;
     
121. 121.    private JFileChooser chooser;
     
122. 122.    private String defaultExtension = "gif";
     
123. 123. }

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