jcombobox.java

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   */
  public void setRenderer(ListCellRenderer aRenderer)
  {
    if (renderer != aRenderer)
      {
	ListCellRenderer oldRenderer = renderer;
	renderer = aRenderer;
	firePropertyChange("renderer", oldRenderer,
	                   renderer);
      }
  }

  /**
   * This method returns renderer responsible for rendering selected item in
   * the combo box
   *
   * @return ListCellRenderer
   */
  public ListCellRenderer getRenderer()
  {
    return renderer;
  }

  /**
   * Sets editor for this JComboBox
   *
   * @param newEditor ComboBoxEditor for this JComboBox. This method fires
   *        PropertyChangeEvent when 'editor' property is changed.
   */
  public void setEditor(ComboBoxEditor newEditor)
  {
    if (editor == newEditor)
      return;

    if (editor != null)
      editor.removeActionListener(this);

    ComboBoxEditor oldEditor = editor;
    editor = newEditor;

    if (editor != null)
      editor.addActionListener(this);

    firePropertyChange("editor", oldEditor, editor);
  }

  /**
   * Returns editor component that is responsible for displaying/editing
   * selected item in the combo box.
   *
   * @return ComboBoxEditor
   */
  public ComboBoxEditor getEditor()
  {
    return editor;
  }

  /**
   * Forces combo box to select given item
   *
   * @param item element in the combo box to select.
   */
  public void setSelectedItem(Object item)
  {
    dataModel.setSelectedItem(item);
  }

  /**
   * Returns currently selected item in the combo box.
   * The result may be <code>null</code> to indicate that nothing is
   * currently selected.
   *
   * @return element that is currently selected in this combo box.
   */
  public Object getSelectedItem()
  {
    return dataModel.getSelectedItem();
  }

  /**
   * Forces JComboBox to select component located in the given index in the
   * combo box.
   * <p>If the index is below -1 or exceeds the upper bound an
   * <code>IllegalArgumentException</code> is thrown.<p/>
   * <p>If the index is -1 then no item gets selected.</p>
   *
   * @param index index specifying location of the component that  should be
   *        selected.
   */
  public void setSelectedIndex(int index)
  {
  	if(index < -1 || index >= dataModel.getSize()) {
  		// Fails because index is out of bounds. 
  		throw new IllegalArgumentException("illegal index: " + index);
  	} else {
  		/* Selects the item at the given index or clears the selection if the
  		 * index value is -1.
  		 */
		setSelectedItem((index == -1) ? null : dataModel.getElementAt(index));
  	}
  }

  /**
   * Returns index of the item that is currently selected  in the combo box.
   * If no item is currently selected, then -1 is returned.
   * 
   * <p>Note: For performance reasons you should minimize invocation of this
   * method. If the data model is not an instance of
   * <code>DefaultComboBoxModel</code> the complexity is O(n) where
   * n is the number of elements in the combo box.</p>
   *
   * @return int Index specifying location of the currently selected item in
   *         the combo box or -1 if nothing is selected in the combo box.
   */
  public int getSelectedIndex()
  {
    Object selectedItem = getSelectedItem();
    
    if (selectedItem != null) {
	
		if(dataModel instanceof DefaultComboBoxModel) {
			// Uses special method of DefaultComboBoxModel to retrieve the index.
        	  	return ((DefaultComboBoxModel) dataModel).getIndexOf(selectedItem);
		} else {
			// Iterates over all items to retrieve the index.
			int size = dataModel.getSize();
			
	  		for(int i=0; i < size; i++) {
	  			Object o = dataModel.getElementAt(i);
	  			
				// XXX: Is special handling of ComparableS neccessary?
	  			if((selectedItem != null) ? selectedItem.equals(o) : o == null) {
	  				return i;
	  			}
	  		}
		}
    }

    // returns that no item is currently selected
    return -1;
  }

  public Object getPrototypeDisplayValue()
  {
    return prototypeDisplayValue;
  }

  public void setPrototypeDisplayValue(Object newPrototypeDisplayValue)
  {
    prototypeDisplayValue = newPrototypeDisplayValue;
  }

  /**
   * This method adds given element to this JComboBox.
   * <p>A <code>RuntimeException</code> is thrown if the data model is not
   * an instance of {@link MutableComboBoxModel}.</p>
   *
   * @param element element to add
   */
  public void addItem(Object element)
  {
  	if(dataModel instanceof MutableComboBoxModel) {
		((MutableComboBoxModel) dataModel).addElement(element);
  	} else {
  		throw new RuntimeException("Unable to add the item because the data model it is not an instance of MutableComboBoxModel.");
  	}
  }

  /**
   * Inserts given element at the specified index to this JComboBox.
   * <p>A <code>RuntimeException</code> is thrown if the data model is not
   * an instance of {@link MutableComboBoxModel}.</p>
   *
   * @param element element to insert
   * @param index position where to insert the element
   */
  public void insertItemAt(Object element, int index)
  {
	if(dataModel instanceof MutableComboBoxModel) {
		((MutableComboBoxModel) dataModel).insertElementAt(element, index);
	} else {
		throw new RuntimeException("Unable to insert the item because the data model it is not an instance of MutableComboBoxModel.");
	}
  }

  /**
   * This method removes given element from this JComboBox.
   * <p>A <code>RuntimeException</code> is thrown if the data model is not
   * an instance of {@link MutableComboBoxModel}.</p>
   *
   * @param element element to remove
   */
  public void removeItem(Object element)
  {
	if(dataModel instanceof MutableComboBoxModel) {
		((MutableComboBoxModel) dataModel).removeElement(element);
	} else {
		throw new RuntimeException("Unable to remove the item because the data model it is not an instance of MutableComboBoxModel.");
	}
  }

  /**
   * This method remove element location in the specified index in the
   * JComboBox.
   * <p>A <code>RuntimeException</code> is thrown if the data model is not
   * an instance of {@link MutableComboBoxModel}.</p>
   *
   * @param index index specifying position of the element to remove
   */
  public void removeItemAt(int index)
  {
	if(dataModel instanceof MutableComboBoxModel) {
		((MutableComboBoxModel) dataModel).removeElementAt(index);
	} else {
		throw new RuntimeException("Unable to remove the item because the data model it is not an instance of MutableComboBoxModel.");
	}
  }

  /**
   * This method removes all elements from this JComboBox.
   * <p>A <code>RuntimeException</code> is thrown if the data model is not
   * an instance of {@link MutableComboBoxModel}.</p>
   * 
   */
  public void removeAllItems()
  {
    if (dataModel instanceof DefaultComboBoxModel) {
    	// Uses special method if we have a DefaultComboBoxModel.
	((DefaultComboBoxModel) dataModel).removeAllElements();
    } else if(dataModel instanceof MutableComboBoxModel){
    	// Iterates over all items and removes each.
    	MutableComboBoxModel mcbm = (MutableComboBoxModel) dataModel;

	/* We intentionally remove the items backwards to support
	 * models which shift their content to the beginning (e.g.
	 * linked lists) 
	 */     	
    	for(int i=mcbm.getSize()-1; i >= 0; i--) {
    		mcbm.removeElementAt(i);
    	}
    	
    } else {
	throw new RuntimeException("Unable to remove the items because the data model it is not an instance of MutableComboBoxModel.");
    }
      
  }

  /**
   * This method displays popup with list of combo box's items on the screen
   */
  public void showPopup()
  {
    setPopupVisible(true);
  }

  /**
   * This method hides popup containing list of combo box's items
   */
  public void hidePopup()
  {
    setPopupVisible(false);
  }

  /**
   * This method either displayes or hides the popup containing  list of combo
   * box's items.
   *
   * @param visible show popup if 'visible' is true and hide it otherwise
   */
  public void setPopupVisible(boolean visible)
  {
    getUI().setPopupVisible(this, visible);
  }

  /**
   * Checks if popup is currently visible on the screen.
   *
   * @return boolean true if popup is visible and false otherwise
   */
  public boolean isPopupVisible()
  {
    return getUI().isPopupVisible(this);
  }

  /**
   * This method sets actionCommand to the specified string. ActionEvent fired
   * to this JComboBox  registered ActionListeners will contain this
   * actionCommand.
   *
   * @param aCommand new action command for the JComboBox's ActionEvent
   */
  public void setActionCommand(String aCommand)
  {
    actionCommand = aCommand;
  }

  /**
   * Returns actionCommand associated with the ActionEvent fired by the
   * JComboBox to its registered ActionListeners.
   *
   * @return String actionCommand for the ActionEvent
   */
  public String getActionCommand()
  {
    return actionCommand;
  }

  /**
   * setAction
   *
   * @param a action to set
   */
  public void setAction(Action a)
  {
    Action old = action;
    action = a;
    configurePropertiesFromAction(action);
    if (action != null)
      // FIXME: remove from old action and add to new action 
      // PropertyChangeListener to listen to changes in the action
      addActionListener(action);
  }

  /**
   * This method returns Action that is invoked when selected item is changed
   * in the JComboBox.
   *
   * @return Action
   */
  public Action getAction()
  {
    return action;
  }

  /**
   * Configure properties of the JComboBox by reading properties of specified
   * action. This method always sets the comboBox's "enabled" property to the
   * value of the Action's "enabled" property.
   *
   * @param a An Action to configure the combo box from
   */
  protected void configurePropertiesFromAction(Action a)
  {
    if (a == null)
      {
	setEnabled(true);
	setToolTipText(null);
      }
    else
      {
	setEnabled(a.isEnabled());
	setToolTipText((String) (a.getValue(Action.SHORT_DESCRIPTION)));
      }
  }

  /**
   * Creates PropertyChangeListener to listen for the changes in comboBox's
   * action properties.
   *
   * @param action action to listen to for property changes
   *
   * @return $PropertyChangeListener$ Listener that listens to changes in
   *         action properties.
   */
  protected PropertyChangeListener createActionPropertyChangeListener(Action action)
  {
    return new PropertyChangeListener()
      {
	public void propertyChange(PropertyChangeEvent e)
	{
	  Action act = (Action) (e.getSource());
	  configurePropertiesFromAction(act);
	}
      };
  }

  /**
   * This method fires ItemEvent to this JComboBox's registered ItemListeners.
   * This method is invoked when currently selected item in this combo box
   * has changed.
   *
   * @param e the ItemEvent describing the change in the combo box's
   *        selection.
   */
  protected void fireItemStateChanged(ItemEvent e)
  {
    ItemListener[] ll = getItemListeners();

    for (int i = 0; i < ll.length; i++)
      ll[i].itemStateChanged(e);
  }

  /**
   * This method fires ActionEvent to this JComboBox's registered
   * ActionListeners. This method is invoked when user explicitly changes
   * currently selected item.
   */
  protected void fireActionEvent()
  {
    ActionListener[] ll = getActionListeners();

    for (int i = 0; i < ll.length; i++)
      ll[i].actionPerformed(new ActionEvent(this,
                                            ActionEvent.ACTION_PERFORMED,
                                            actionCommand));
  }