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org.gui4j.component
Class Gui4jTree.Gui4jTreeSelectionListener  

java.lang.Object
  org.gui4j.component.Gui4jTree.Gui4jTreeSelectionListener

All Implemented Interfaces:

java.util.EventListener, java.awt.event.FocusListener, java.awt.event.KeyListener, javax.swing.event.TreeSelectionListener

Enclosing class:

Gui4jTree

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private abstract static class Gui4jTree.Gui4jTreeSelectionListener

extends java.lang.Object

implements javax.swing.event.TreeSelectionListener, java.awt.event.KeyListener, java.awt.event.FocusListener

Subclass of TreeSelectionListener. Implements a simple strategy to solve the problem that a lot of TreeSelectionEvents are generated and processed when the user keeps pressing the up and down arrow keys. To work correctly, the same instance of this listener must be registered in three ways with a tree, using JTree.addTreeSelectionListener(javax.swing.event.TreeSelectionListener)>JTree.addTreeSelectionListener(javax.swing.event.TreeSelectionListener) 55 , Component.addKeyListener(java.awt.event.KeyListener)>Component.addKeyListener(java.awt.event.KeyListener) 55 and Component.addFocusListener(java.awt.event.FocusListener)>Component.addFocusListener(java.awt.event.FocusListener) 55 .

The problem this class solves is that a TreeSelectionEvent might trigger expensive operations (e.g. loading detailed information for the newly selected tree node from a database). If the user "scrolls down" by pressing the down arrow for a long time, the expensive operation is performed for each visited node. This Listener blocks all TreeSelectionEvents while any key is pressed. Only when a key is released is the most recent event passed to the actual event handler.

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Field Summary
private  javax.swing.event.TreeSelectionEvent	blockedEvent
private  boolean	blockNotification

 

Constructor Summary
private	Gui4jTree.Gui4jTreeSelectionListener()

 

Method Summary
private  void	block()
void	focusGained(java.awt.event.FocusEvent e)           This method is called when a component gains the keyboard focus.
void	focusLost(java.awt.event.FocusEvent e)           This method is invoked when a component loses the keyboard focus.
void	keyPressed(java.awt.event.KeyEvent e)           This method is called when a key is pressed.
void	keyReleased(java.awt.event.KeyEvent e)           This method is called when a key is released.
void	keyTyped(java.awt.event.KeyEvent e)           This method is called when a key is typed.
abstract  void	selectionChanged(javax.swing.event.TreeSelectionEvent e)           Subclasses must override this method instead of the usual TreeSelectionListener.valueChanged(javax.swing.event.TreeSelectionEvent)>TreeSelectionListener.valueChanged(javax.swing.event.TreeSelectionEvent) 55 .
private  void	unblock()
void	valueChanged(javax.swing.event.TreeSelectionEvent e)           Subclasses should not override this method (as is done with a normal TreeSelectionListener) but selectionChanged(TreeSelectionEvent) 55 instead.

 

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Field Detail

blockNotification

private boolean blockNotification

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blockedEvent

private javax.swing.event.TreeSelectionEvent blockedEvent

Constructor Detail

Gui4jTree.Gui4jTreeSelectionListener

private Gui4jTree.Gui4jTreeSelectionListener()

Method Detail

block

private void block()

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unblock

private void unblock()

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selectionChanged

public abstract void selectionChanged(javax.swing.event.TreeSelectionEvent e)

Subclasses must override this method instead of the usual TreeSelectionListener.valueChanged(javax.swing.event.TreeSelectionEvent)>TreeSelectionListener.valueChanged(javax.swing.event.TreeSelectionEvent) 55 .

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valueChanged

public final void valueChanged(javax.swing.event.TreeSelectionEvent e)

Subclasses should not override this method (as is done with a normal TreeSelectionListener) but selectionChanged(TreeSelectionEvent) 55 instead.

Specified by:

valueChanged in interface javax.swing.event.TreeSelectionListener

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keyPressed

public void keyPressed(java.awt.event.KeyEvent e)

Description copied from interface: java.awt.event.KeyListener

This method is called when a key is pressed.

Specified by:

keyPressed in interface java.awt.event.KeyListener

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keyReleased

public void keyReleased(java.awt.event.KeyEvent e)

Description copied from interface: java.awt.event.KeyListener

This method is called when a key is released.

Specified by:

keyReleased in interface java.awt.event.KeyListener

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keyTyped

public void keyTyped(java.awt.event.KeyEvent e)

Description copied from interface: java.awt.event.KeyListener

This method is called when a key is typed. A key is considered typed when it and all modifiers have been pressed and released, mapping to a single virtual key.

Specified by:

keyTyped in interface java.awt.event.KeyListener

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focusGained

public void focusGained(java.awt.event.FocusEvent e)

Description copied from interface: java.awt.event.FocusListener

This method is called when a component gains the keyboard focus.

Specified by:

focusGained in interface java.awt.event.FocusListener

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focusLost

public void focusLost(java.awt.event.FocusEvent e)

Description copied from interface: java.awt.event.FocusListener

This method is invoked when a component loses the keyboard focus.

Specified by:

focusLost in interface java.awt.event.FocusListener

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