Java Reference
In-Depth Information
Example 10•19: PropertyTable.java (continued)
* This method returns the value that appears at the specified row and
* column of the table
**/
public Object getValueAt(int row, int column) {
PropertyDescriptor prop = properties[row];
switch(column) {
case 0: return prop.getName();
case 1: return prop.getPropertyType();
case 2: return getAccessType(prop);
case 3: return new Boolean(prop.isBound());
default: return null;
}
}
// A helper method called from getValueAt() above
String getAccessType(PropertyDescriptor prop) {
java.lang.reflect.Method reader = prop.getReadMethod();
java.lang.reflect.Method writer = prop.getWriteMethod();
if ((reader != null) && (writer != null)) return "Read/Write";
else if (reader != null) return "Read-Only";
else if (writer != null) return "Write-Only";
else return "No Access"; // should never happen
}
}
}
Displaying Trees
The
JTree
component is used to display tree-structured data. If your data is in the
form of nested arrays, vectors, or hashtables, you can simply pass the root node of
the data structure to the
JTree
constructor, and it displays it. Tree data is not typi-
cally in this form, however. In order to display data that is in another form, you
must implement the
javax.swing.Tree.TreeModel
interface to interpret the data in
a way the
JTree
component can use it.
Example 10-20 shows a listing of
ComponentTree.java
,a
JTree
subclass that uses
a custom
TreeModel
implementation to display the containment hierarchy of an
AWT or Swing GUI in tree form. The class includes a
main()
method that uses the
ComponentTree
class to display its own component hierarchy, as shown in Figure
10-16. As with the previous
JTable
example, the key to this example is the
TreeModel
implementation. The
main()
method also illustrates a technique for
responding to tree node selection events.
Example 10•20: ComponentTree.java
package com.davidflanagan.examples.gui;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;
/**
* This class is a JTree subclass that displays the tree of AWT or Swing
* component that make up a GUI.
