DefaultButtonModel.java

/* DefaultButtonModel.java --
   Copyright (C) 2002, 2004, 2006, Free Software Foundation, Inc.

This file is part of GNU Classpath.

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package javax.swing;

import java.awt.ItemSelectable;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.KeyEvent;
import java.io.Serializable;
import java.util.EventListener;

import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.EventListenerList;

/**
 * The default implementation of {@link ButtonModel}.
 * The purpose of this class is to model the dynamic state of an abstract
 * button. The concrete button type holding this state may be a a "toggle"
 * button (checkbox, radio button) or a "push" button (menu button, button).
 * If the model is disabled, only the "selected" property can be changed. An
 * attempt to change the "armed", "rollover" or "pressed" properties  while
 * the model is disabled will be blocked. Any successful (non-blocked) change
 * to the model's properties will trigger the firing of a ChangeEvent. Any
 * change to the "selected" property will trigger the firing of an ItemEvent
 * in addition to ChangeEvent. This is true whether the model is enabled or
 * not. One other state change is special: the transition from "enabled,
 * armed and pressed" to "enabled, armed and not-pressed". This is considered
 * the "trailing edge" of a successful mouse click, and therefore fires an
 * ActionEvent in addition to a ChangeEvent. In all other respects this class
 * is just a container of boolean flags.
 *
 * @author Graydon Hoare (graydon_at_redhat.com)
 */
public class DefaultButtonModel implements ButtonModel, Serializable
{
  /** DOCUMENT ME! */
  private static final long serialVersionUID = -5342609566534980231L;

  /**
   * Indicates that the button is <em>partially</em> committed to being
   * pressed, but not entirely. This usually happens when a user has pressed
   * but not yet released the mouse button.
   */
  public static final int ARMED = 1;

  /**
   * State constant indicating that the button is enabled. Buttons cannot be
   * pressed or selected unless they are enabled.
   */
  public static final int ENABLED = 8;

  /**
   * State constant indicating that the user is holding down the button. When
   * this transitions from true to false, an ActionEvent may be fired,
   * depending on the value of the "armed" property.
   */
  public static final int PRESSED = 4;

  /**
   * State constant indicating that the mouse is currently positioned over the
   * button.
   */
  public static final int ROLLOVER = 16;

  /**
   * State constant indicating that the button is selected. This constant is
   * only meaningful for toggle-type buttons (radio buttons, checkboxes).
   */
  public static final int SELECTED = 2;

  /**
   * Represents the "state properties" (armed, enabled, pressed, rollover and
   * selected) by a bitwise combination of integer constants.
   */
  protected int stateMask = ENABLED;

  /**
   * List of ItemListeners, ChangeListeners, and ActionListeners registered on
   * this model.
   */
  protected EventListenerList listenerList = new EventListenerList();

  /** The single ChangeEvent this model (re)uses to call its ChangeListeners. */
  protected ChangeEvent changeEvent = new ChangeEvent(this);

  /**
   * The group this model belongs to. Only one button in a group may be
   * selected at any given time.
   */
  protected ButtonGroup group;

  /**
   * The key code (one of {@link java.awt.event.KeyEvent} VK_) used to press
   * this button via a keyboard interface.
   */
  protected int mnemonic = KeyEvent.VK_UNDEFINED;

  /**
   * The string used as the "command" property of any ActionEvent this model
   * sends.
   */
  protected String actionCommand;

  /**
   * Creates a new DefaultButtonModel object.
   */
  public DefaultButtonModel()
  {
    // Nothing to do here.
  }

  /**
   * Return <code>null</code>. Use {@link AbstractButton} if you wish to
   * interface with a button via an {@link ItemSelectable} interface.
   *
   * @return <code>null</code>
   */
  public Object[] getSelectedObjects()
  {
    return null;
  }

  /**
   * Returns a specified class of listeners.
   *
   * @param listenerType the type of listener to return
   *
   * @return array of listeners
   */
  public <T extends EventListener> T[] getListeners(Class<T> listenerType)
  {
    return listenerList.getListeners(listenerType);
  }

  /**
   * Add an ActionListener to the model. Usually only called to subscribe an
   * AbstractButton's listener to the model.
   *
   * @param l The listener to add
   */
  public void addActionListener(ActionListener l)
  {
    listenerList.add(ActionListener.class, l);
  }

  /**
   * Remove an ActionListener to the model. Usually only called to unsubscribe
   * an AbstractButton's listener to the model.
   *
   * @param l The listener to remove
   */
  public void removeActionListener(ActionListener l)
  {
    listenerList.remove(ActionListener.class, l);
  }

  /**
   * Returns all registered <code>ActionListener</code> objects.
   *
   * @return array of <code>ActionListener</code> objects
   */
  public ActionListener[] getActionListeners()
  {
    return (ActionListener[]) listenerList.getListeners(ActionListener.class);
  }

  /**
   * Add an ItemListener to the model. Usually only called to subscribe an
   * AbstractButton's listener to the model.
   *
   * @param l The listener to add
   */
  public void addItemListener(ItemListener l)
  {
    listenerList.add(ItemListener.class, l);
  }

  /**
   * Remove an ItemListener to the model. Usually only called to unsubscribe
   * an AbstractButton's listener to the model.
   *
   * @param l The listener to remove
   */
  public void removeItemListener(ItemListener l)
  {
    listenerList.remove(ItemListener.class, l);
  }

  /**
   * Returns all registered <code>ItemListener</code> objects.
   *
   * @return array of <code>ItemListener</code> objects
   */
  public ItemListener[] getItemListeners()
  {
    return (ItemListener[]) listenerList.getListeners(ItemListener.class);
  }

  /**
   * Add a ChangeListener to the model. Usually only called to subscribe an
   * AbstractButton's listener to the model.
   *
   * @param l The listener to add
   */
  public void addChangeListener(ChangeListener l)
  {
    listenerList.add(ChangeListener.class, l);
  }

  /**
   * Remove a ChangeListener to the model. Usually only called to unsubscribe
   * an AbstractButton's listener to the model.
   *
   * @param l The listener to remove
   */
  public void removeChangeListener(ChangeListener l)
  {
    listenerList.remove(ChangeListener.class, l);
  }

  /**
   * Returns all registered <code>ChangeListener</code> objects.
   *
   * @return array of <code>ChangeListener</code> objects
   */
  public ChangeListener[] getChangeListeners()
  {
    return (ChangeListener[]) listenerList.getListeners(ChangeListener.class);
  }

  /**
   * Inform each ItemListener in the {@link #listenerList} that an ItemEvent
   * has occurred. This happens in response to any change to the {@link
   * #stateMask} field.
   *
   * @param e The ItemEvent to fire
   */
  protected void fireItemStateChanged(ItemEvent e)
  {
    ItemListener[] ll = getItemListeners();

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

  /**
   * Inform each ActionListener in the {@link #listenerList} that an
   * ActionEvent has occurred. This happens in response to the any change to
   * the {@link #stateMask} field which makes the enabled, armed and pressed
   * properties all simultaneously <code>true</code>.
   *
   * @param e The ActionEvent to fire
   */
  protected void fireActionPerformed(ActionEvent e)
  {
    ActionListener[] ll = getActionListeners();

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

  /**
   * Inform each ChangeListener in the {@link #listenerList} that a ChangeEvent
   * has occurred. This happens in response to the any change to a property
   * of the model.
   */
  protected void fireStateChanged()
  {
    ChangeListener[] ll = getChangeListeners();

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

  /**
   * Get the value of the model's "armed" property.
   *
   * @return The current "armed" property
   */
  public boolean isArmed()
  {
    return (stateMask & ARMED) == ARMED;
  }

  /**
   * Set the value of the model's "armed" property.
   *
   * @param a The new "armed" property
   */
  public void setArmed(boolean a)
  {
    // if this call does not represent a CHANGE in state, then return
    if ((a && isArmed()) || (!a && !isArmed()))
      return;
    
    // cannot change ARMED state unless button is enabled
    if (!isEnabled())
      return;

    // make the change
    if (a)
      stateMask = stateMask | ARMED;
    else
      stateMask = stateMask & (~ARMED);

    // notify interested ChangeListeners
    fireStateChanged();
  }

  /**
   * Get the value of the model's "enabled" property.
   *
   * @return The current "enabled" property.
   */
  public boolean isEnabled()
  {
    return (stateMask & ENABLED) == ENABLED;
  }

  /**
   * Set the value of the model's "enabled" property.
   *
   * @param e The new "enabled" property
   */
  public void setEnabled(boolean e)
  {
    // if this call does not represent a CHANGE in state, then return
    if ((e && isEnabled()) || (!e && !isEnabled()))
      return;

    // make the change
    if (e)
      stateMask = stateMask | ENABLED;
    else
      stateMask = stateMask & (~ENABLED) & (~ARMED) & (~PRESSED);

    // notify interested ChangeListeners
    fireStateChanged();
  }

  /**
   * Set the value of the model's "pressed" property.
   *
   * @param p The new "pressed" property
   */
  public void setPressed(boolean p)
  {
    // if this call does not represent a CHANGE in state, then return
    if ((p && isPressed()) || (!p && !isPressed()))
      return;

    // cannot changed PRESSED state unless button is enabled
    if (!isEnabled())
      return;

    // make the change
    if (p)
      stateMask = stateMask | PRESSED;
    else
      stateMask = stateMask & (~PRESSED);

    // if button is armed and was released, fire action event
    if (!p && isArmed())
      fireActionPerformed(new ActionEvent(this, ActionEvent.ACTION_PERFORMED,
                                          actionCommand));

    // notify interested ChangeListeners
    fireStateChanged();
  }

  /**
   * Get the value of the model's "pressed" property.
   *
   * @return The current "pressed" property
   */
  public boolean isPressed()
  {
    return (stateMask & PRESSED) == PRESSED;
  }

  /**
   * Set the value of the model's "rollover" property.
   *
   * @param r The new "rollover" property
   */
  public void setRollover(boolean r)
  {
    // if this call does not represent a CHANGE in state, then return
    if (r == isRollover())
      return;
    
    // cannot set ROLLOVER property unless button is enabled
    if (!isEnabled())
      return;

    // make the change
    if (r)
      stateMask = stateMask | ROLLOVER;
    else
      stateMask = stateMask & (~ROLLOVER);

    // notify interested ChangeListeners
    fireStateChanged();
  }

  /**
   * Set the value of the model's "selected" property.
   *
   * @param s The new "selected" property
   */
  public void setSelected(boolean s)
  {
    // if this call does not represent a CHANGE in state, then return
    if ((s && isSelected()) || (!s && !isSelected()))
      return;
    
    // make the change
    if (s)
      stateMask = stateMask | SELECTED;
    else
      stateMask = stateMask & (~SELECTED);

    // notify interested ChangeListeners
    fireStateChanged();

    // fire ItemStateChanged events
    if (s)
      {
        fireItemStateChanged(new ItemEvent(this, ItemEvent.ITEM_STATE_CHANGED,
                                           this, ItemEvent.SELECTED));
        if (group != null)
          group.setSelected(this, true);
      }
    else
      {
        fireItemStateChanged(new ItemEvent(this, ItemEvent.ITEM_STATE_CHANGED,
                                           this, ItemEvent.DESELECTED));
        if (group != null)
          group.setSelected(this, false);
      }
  }

  /**
   * Get the value of the model's "selected" property.
   *
   * @return The current "selected" property
   */
  public boolean isSelected()
  {
    return (stateMask & SELECTED) == SELECTED;
  }

  /**
   * Get the value of the model's "rollover" property.
   *
   * @return The current "rollover" property
   */
  public boolean isRollover()
  {
    return (stateMask & ROLLOVER) == ROLLOVER;
  }

  /**
   * Get the value of the model's "mnemonic" property.
   *
   * @return The current "mnemonic" property
   */
  public int getMnemonic()
  {
    return mnemonic;
  }

  /**
   * Set the value of the model's "mnemonic" property.
   *
   * @param key The new "mnemonic" property
   */
  public void setMnemonic(int key)
  {
    if (mnemonic != key)
      {
        mnemonic = key;
        fireStateChanged();
      }
  }

  /**
   * Set the value of the model's "actionCommand" property. This property is
   * used as the "command" property of the {@link ActionEvent} fired from the
   * model.
   *
   * @param s The new "actionCommand" property.
   */
  public void setActionCommand(String s)
  {
    if (actionCommand != s)
      {
        actionCommand = s;
        fireStateChanged();
      }
  }

  /**
   * Returns the current value of the model's "actionCommand" property.
   *
   * @return The current "actionCommand" property
   */
  public String getActionCommand()
  {
    return actionCommand;
  }

  /**
   * Set the value of the model's "group" property. The model is said to be a
   * member of the {@link ButtonGroup} held in its "group" property, and only
   * one model in a given group can have their "selected" property be
   * <code>true</code> at a time.
   *
   * @param g The new "group" property (<code>null</code> permitted).
   * 
   * @see #getGroup()
   */
  public void setGroup(ButtonGroup g)
  {
    group = g;
  }

  /**
   * Returns the current value of the model's "group" property.
   *
   * @return The value of the "group" property
   * 
   * @see #setGroup(ButtonGroup)
   */
  public ButtonGroup getGroup()
  {
    return group;
  }
}