File	Doc	Category	Size	Date	Package
Scrollbar.java	API Doc	Java SE 5 API	46115	Fri Aug 26 14:56:46 BST 2005	java.awt

Scrollbar

• java.lang.Object
  • java.awt.Component

Fields Summary
public static final int	HORIZONTAL A constant that indicates a horizontal scroll bar.
public static final int	VERTICAL A constant that indicates a vertical scroll bar.
int	value The value of the Scrollbar. This property must be greater than or equal to minimum and less than or equal to maximum - visibleAmount
int	maximum The maximum value of the Scrollbar. This value must be greater than the minimum value.
int	minimum The minimum value of the Scrollbar. This value must be less than the maximum value.
int	visibleAmount The size of the Scrollbar's bubble. When a scroll bar is used to select a range of values, the visibleAmount represents the size of this range. This is visually indicated by the size of the bubble.
int	orientation The Scrollbar's orientation--being either horizontal or vertical. This value should be specified when the scrollbar is created. orientation can be either : VERTICAL or HORIZONTAL only.
int	lineIncrement The amount by which the scrollbar value will change when going up or down by a line. This value must be greater than zero.
int	pageIncrement The amount by which the scrollbar value will change when going up or down by a page. This value must be greater than zero.
transient boolean	isAdjusting The adjusting status of the Scrollbar. True if the value is in the process of changing as a result of actions being taken by the user.
transient AdjustmentListener	adjustmentListener
private static final String	base
private static int	nameCounter
private static final long	serialVersionUID
private int	scrollbarSerializedDataVersion The scroll bar's serialized Data Version.

Constructors Summary
public Scrollbar() Constructs a new vertical scroll bar. The default properties of the scroll bar are listed in the following table: Property Description Default Value orientation indicates whether the scroll bar is vertical or horizontal Scrollbar.VERTICAL value value which controls the location of the scroll bar's bubble 0 visible amount visible amount of the scroll bar's range, typically represented by the size of the scroll bar's bubble 10 minimum minimum value of the scroll bar 0 maximum maximum value of the scroll bar 100 unit increment amount the value changes when the Line Up or Line Down key is pressed, or when the end arrows of the scrollbar are clicked 1 block increment amount the value changes when the Page Up or Page Down key is pressed, or when the scrollbar track is clicked on either side of the bubble 10 exception HeadlessException if GraphicsEnvironment.isHeadless() returns true. see java.awt.GraphicsEnvironment#isHeadless /* ensure that the necessary native libraries are loaded */ Toolkit.loadLibraries(); if (!GraphicsEnvironment.isHeadless()) { initIDs(); } this(VERTICAL, 0, 10, 0, 100);
public Scrollbar(int orientation) Constructs a new scroll bar with the specified orientation. The orientation argument must take one of the two values Scrollbar.HORIZONTAL, or Scrollbar.VERTICAL, indicating a horizontal or vertical scroll bar, respectively. param orientation indicates the orientation of the scroll bar exception IllegalArgumentException when an illegal value for the orientation argument is supplied exception HeadlessException if GraphicsEnvironment.isHeadless() returns true. see java.awt.GraphicsEnvironment#isHeadless this(orientation, 0, 10, 0, 100);
public Scrollbar(int orientation, int value, int visible, int minimum, int maximum) Constructs a new scroll bar with the specified orientation, initial value, visible amount, and minimum and maximum values. The orientation argument must take one of the two values Scrollbar.HORIZONTAL, or Scrollbar.VERTICAL, indicating a horizontal or vertical scroll bar, respectively. The parameters supplied to this constructor are subject to the constraints described in {@link #setValues(int, int, int, int)}. param orientation indicates the orientation of the scroll bar. param value the initial value of the scroll bar param visible the visible amount of the scroll bar, typically represented by the size of the bubble param minimum the minimum value of the scroll bar param maximum the maximum value of the scroll bar exception IllegalArgumentException when an illegal value for the orientation argument is supplied exception HeadlessException if GraphicsEnvironment.isHeadless() returns true. see #setValues see java.awt.GraphicsEnvironment#isHeadless GraphicsEnvironment.checkHeadless(); switch (orientation) { case HORIZONTAL: case VERTICAL: this.orientation = orientation; break; default: throw new IllegalArgumentException("illegal scrollbar orientation"); } setValues(value, visible, minimum, maximum);

Methods Summary
public synchronized void	addAdjustmentListener(java.awt.event.AdjustmentListener l) Adds the specified adjustment listener to receive instances of AdjustmentEvent from this scroll bar. If l is null, no exception is thrown and no action is performed. param l the adjustment listener see #removeAdjustmentListener see #getAdjustmentListeners see java.awt.event.AdjustmentEvent see java.awt.event.AdjustmentListener since JDK1.1 if (l == null) { return; } adjustmentListener = AWTEventMulticaster.add(adjustmentListener, l); newEventsOnly = true;
public void	addNotify() Creates the Scrollbar's peer. The peer allows you to modify the appearance of the Scrollbar without changing any of its functionality. synchronized (getTreeLock()) { if (peer == null) peer = getToolkit().createScrollbar(this); super.addNotify(); }
java.lang.String	constructComponentName() Constructs a name for this component. Called by getName when the name is null. synchronized (getClass()) { return base + nameCounter++; }
boolean	eventEnabled(java.awt.AWTEvent e) if (e.id == AdjustmentEvent.ADJUSTMENT_VALUE_CHANGED) { if ((eventMask & AWTEvent.ADJUSTMENT_EVENT_MASK) != 0 || adjustmentListener != null) { return true; } return false; } return super.eventEnabled(e);
public javax.accessibility.AccessibleContext	getAccessibleContext() Gets the AccessibleContext associated with this Scrollbar. For scrollbars, the AccessibleContext takes the form of an AccessibleAWTScrollBar. A new AccessibleAWTScrollBar instance is created if necessary. return an AccessibleAWTScrollBar that serves as the AccessibleContext of this ScrollBar if (accessibleContext == null) { accessibleContext = new AccessibleAWTScrollBar(); } return accessibleContext;
public synchronized java.awt.event.AdjustmentListener[]	getAdjustmentListeners() Returns an array of all the adjustment listeners registered on this scrollbar. return all of this scrollbar's AdjustmentListeners or an empty array if no adjustment listeners are currently registered see #addAdjustmentListener see #removeAdjustmentListener see java.awt.event.AdjustmentEvent see java.awt.event.AdjustmentListener since 1.4 return (AdjustmentListener[])(getListeners(AdjustmentListener.class));
public int	getBlockIncrement() Gets the block increment of this scroll bar. The block increment is the value that is added or subtracted when the user activates the block increment area of the scroll bar, generally through a mouse or keyboard gesture that the scroll bar receives as an adjustment event. The block increment must be greater than zero. return the block increment of this scroll bar see java.awt.Scrollbar#setBlockIncrement since JDK1.1 return getPageIncrement();
public int	getLineIncrement() deprecated As of JDK version 1.1, replaced by getUnitIncrement(). return lineIncrement;
public T[]	getListeners(java.lang.Class listenerType) Returns an array of all the objects currently registered as FooListeners upon this Scrollbar. FooListeners are registered using the addFooListener method. You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a Scrollbar c for its mouse listeners with the following code: MouseListener[] mls = (MouseListener[])(c.getListeners(MouseListener.class)); If no such listeners exist, this method returns an empty array. param listenerType the type of listeners requested; this parameter should specify an interface that descends from java.util.EventListener return an array of all objects registered as FooListeners on this component, or an empty array if no such listeners have been added exception ClassCastException if listenerType doesn't specify a class or interface that implements java.util.EventListener since 1.3 EventListener l = null; if (listenerType == AdjustmentListener.class) { l = adjustmentListener; } else { return super.getListeners(listenerType); } return AWTEventMulticaster.getListeners(l, listenerType);
public int	getMaximum() Gets the maximum value of this scroll bar. return the maximum value of this scroll bar see java.awt.Scrollbar#getValue see java.awt.Scrollbar#getMinimum return maximum;
public int	getMinimum() Gets the minimum value of this scroll bar. return the minimum value of this scroll bar see java.awt.Scrollbar#getValue see java.awt.Scrollbar#getMaximum return minimum;
public int	getOrientation() Returns the orientation of this scroll bar. return the orientation of this scroll bar, either Scrollbar.HORIZONTAL or Scrollbar.VERTICAL see java.awt.Scrollbar#setOrientation return orientation;
public int	getPageIncrement() deprecated As of JDK version 1.1, replaced by getBlockIncrement(). return pageIncrement;
public int	getUnitIncrement() Gets the unit increment for this scrollbar. The unit increment is the value that is added or subtracted when the user activates the unit increment area of the scroll bar, generally through a mouse or keyboard gesture that the scroll bar receives as an adjustment event. The unit increment must be greater than zero. return the unit increment of this scroll bar see java.awt.Scrollbar#setUnitIncrement since JDK1.1 return getLineIncrement();
public int	getValue() Gets the current value of this scroll bar. return the current value of this scroll bar see java.awt.Scrollbar#getMinimum see java.awt.Scrollbar#getMaximum return value;
public boolean	getValueIsAdjusting() Returns true if the value is in the process of changing as a result of actions being taken by the user. return the value of the valueIsAdjusting property see #setValueIsAdjusting since 1.4 return isAdjusting;
public int	getVisible() deprecated As of JDK version 1.1, replaced by getVisibleAmount(). return visibleAmount;
public int	getVisibleAmount() Gets the visible amount of this scroll bar. When a scroll bar is used to select a range of values, the visible amount is used to represent the range of values that are currently visible. The size of the scroll bar's bubble (also called a thumb or scroll box), usually gives a visual representation of the relationship of the visible amount to the range of the scroll bar. The scroll bar's bubble may not be displayed when it is not moveable (e.g. when it takes up the entire length of the scroll bar's track, or when the scroll bar is disabled). Whether the bubble is displayed or not will not affect the value returned by getVisibleAmount. return the visible amount of this scroll bar see java.awt.Scrollbar#setVisibleAmount since JDK1.1 return getVisible();
private static native void	initIDs() Initialize JNI field and method IDs.
protected java.lang.String	paramString() Returns a string representing the state of this Scrollbar. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be null. return the parameter string of this scroll bar return super.paramString() + ",val=" + value + ",vis=" + visibleAmount + ",min=" + minimum + ",max=" + maximum + ((orientation == VERTICAL) ? ",vert" : ",horz") + ",isAdjusting=" + isAdjusting;
protected void	processAdjustmentEvent(java.awt.event.AdjustmentEvent e) Processes adjustment events occurring on this scrollbar by dispatching them to any registered AdjustmentListener objects. This method is not called unless adjustment events are enabled for this component. Adjustment events are enabled when one of the following occurs: An AdjustmentListener object is registered via addAdjustmentListener. Adjustment events are enabled via enableEvents. Note that if the event parameter is null the behavior is unspecified and may result in an exception. param e the adjustment event see java.awt.event.AdjustmentEvent see java.awt.event.AdjustmentListener see java.awt.Scrollbar#addAdjustmentListener see java.awt.Component#enableEvents since JDK1.1 AdjustmentListener listener = adjustmentListener; if (listener != null) { listener.adjustmentValueChanged(e); }
protected void	processEvent(java.awt.AWTEvent e) Processes events on this scroll bar. If the event is an instance of AdjustmentEvent, it invokes the processAdjustmentEvent method. Otherwise, it invokes its superclass's processEvent method. Note that if the event parameter is null the behavior is unspecified and may result in an exception. param e the event see java.awt.event.AdjustmentEvent see java.awt.Scrollbar#processAdjustmentEvent since JDK1.1 if (e instanceof AdjustmentEvent) { processAdjustmentEvent((AdjustmentEvent)e); return; } super.processEvent(e);
private void	readObject(java.io.ObjectInputStream s) Reads the ObjectInputStream and if it isn't null adds a listener to receive adjustment events fired by the Scrollbar. Unrecognized keys or values will be ignored. param s the ObjectInputStream to read exception HeadlessException if GraphicsEnvironment.isHeadless returns true see java.awt.GraphicsEnvironment#isHeadless see #writeObject(ObjectOutputStream) GraphicsEnvironment.checkHeadless(); s.defaultReadObject(); Object keyOrNull; while(null != (keyOrNull = s.readObject())) { String key = ((String)keyOrNull).intern(); if (adjustmentListenerK == key) addAdjustmentListener((AdjustmentListener)(s.readObject())); else // skip value for unrecognized key s.readObject(); }
public synchronized void	removeAdjustmentListener(java.awt.event.AdjustmentListener l) Removes the specified adjustment listener so that it no longer receives instances of AdjustmentEvent from this scroll bar. If l is null, no exception is thrown and no action is performed. param l the adjustment listener see #addAdjustmentListener see #getAdjustmentListeners see java.awt.event.AdjustmentEvent see java.awt.event.AdjustmentListener since JDK1.1 if (l == null) { return; } adjustmentListener = AWTEventMulticaster.remove(adjustmentListener, l);
public void	setBlockIncrement(int v) Sets the block increment for this scroll bar. The block increment is the value that is added or subtracted when the user activates the block increment area of the scroll bar, generally through a mouse or keyboard gesture that the scroll bar receives as an adjustment event. The block increment must be greater than zero. Attepts to set the block increment to a value lower than 1 will result in a value of 1 being set. param v the amount by which to increment or decrement the scroll bar's value see java.awt.Scrollbar#getBlockIncrement since JDK1.1 setPageIncrement(v);
public synchronized void	setLineIncrement(int v) deprecated As of JDK version 1.1, replaced by setUnitIncrement(int). int tmp = (v < 1) ? 1 : v; if (lineIncrement == tmp) { return; } lineIncrement = tmp; ScrollbarPeer peer = (ScrollbarPeer)this.peer; if (peer != null) { peer.setLineIncrement(lineIncrement); }
public void	setMaximum(int newMaximum) Sets the maximum value of this scroll bar. When setMaximum is called, the maximum value is changed, and other values (including the minimum, the visible amount, and the current scroll bar value) are changed to be consistent with the new maximum. Normally, a program should change a scroll bar's maximum value only by calling setValues. The setValues method simultaneously and synchronously sets the minimum, maximum, visible amount, and value properties of a scroll bar, so that they are mutually consistent. Note that setting the maximum value to Integer.MIN_VALUE will result in the new maximum value being set to Integer.MIN_VALUE + 1. param newMaximum the new maximum value for this scroll bar see java.awt.Scrollbar#setValues see java.awt.Scrollbar#setMinimum since JDK1.1 // minimum is checked first in setValues, so we need to // enforce minimum and maximum checks here. if (newMaximum == Integer.MIN_VALUE) { newMaximum = Integer.MIN_VALUE + 1; } if (minimum >= newMaximum) { minimum = newMaximum - 1; } // Use setValues so that a consistent policy relating // minimum, maximum, visible amount, and value is enforced. setValues(value, visibleAmount, minimum, newMaximum);
public void	setMinimum(int newMinimum) Sets the minimum value of this scroll bar. When setMinimum is called, the minimum value is changed, and other values (including the maximum, the visible amount, and the current scroll bar value) are changed to be consistent with the new minimum. Normally, a program should change a scroll bar's minimum value only by calling setValues. The setValues method simultaneously and synchronously sets the minimum, maximum, visible amount, and value properties of a scroll bar, so that they are mutually consistent. Note that setting the minimum value to Integer.MAX_VALUE will result in the new minimum value being set to Integer.MAX_VALUE - 1. param newMinimum the new minimum value for this scroll bar see java.awt.Scrollbar#setValues see java.awt.Scrollbar#setMaximum since JDK1.1 // No checks are necessary in this method since minimum is // the first variable checked in the setValues function. // Use setValues so that a consistent policy relating // minimum, maximum, visible amount, and value is enforced. setValues(value, visibleAmount, newMinimum, maximum);
public void	setOrientation(int orientation) Sets the orientation for this scroll bar. param orientation the orientation of this scroll bar, either Scrollbar.HORIZONTAL or Scrollbar.VERTICAL see java.awt.Scrollbar#getOrientation exception IllegalArgumentException if the value supplied for orientation is not a legal value since JDK1.1 synchronized (getTreeLock()) { if (orientation == this.orientation) { return; } switch (orientation) { case HORIZONTAL: case VERTICAL: this.orientation = orientation; break; default: throw new IllegalArgumentException("illegal scrollbar orientation"); } /* Create a new peer with the specified orientation. */ if (peer != null) { removeNotify(); addNotify(); invalidate(); } } if (accessibleContext != null) { accessibleContext.firePropertyChange( AccessibleContext.ACCESSIBLE_STATE_PROPERTY, ((orientation == VERTICAL) ? AccessibleState.HORIZONTAL : AccessibleState.VERTICAL), ((orientation == VERTICAL) ? AccessibleState.VERTICAL : AccessibleState.HORIZONTAL)); }
public synchronized void	setPageIncrement(int v) deprecated As of JDK version 1.1, replaced by setBlockIncrement(). int tmp = (v < 1) ? 1 : v; if (pageIncrement == tmp) { return; } pageIncrement = tmp; ScrollbarPeer peer = (ScrollbarPeer)this.peer; if (peer != null) { peer.setPageIncrement(pageIncrement); }
public void	setUnitIncrement(int v) Sets the unit increment for this scroll bar. The unit increment is the value that is added or subtracted when the user activates the unit increment area of the scroll bar, generally through a mouse or keyboard gesture that the scroll bar receives as an adjustment event. The unit increment must be greater than zero. Attepts to set the unit increment to a value lower than 1 will result in a value of 1 being set. param v the amount by which to increment or decrement the scroll bar's value see java.awt.Scrollbar#getUnitIncrement since JDK1.1 setLineIncrement(v);
public void	setValue(int newValue) Sets the value of this scroll bar to the specified value. If the value supplied is less than the current minimum or greater than the current maximum - visibleAmount, then either minimum or maximum - visibleAmount is substituted, as appropriate. Normally, a program should change a scroll bar's value only by calling setValues. The setValues method simultaneously and synchronously sets the minimum, maximum, visible amount, and value properties of a scroll bar, so that they are mutually consistent. Calling this method does not fire an AdjustmentEvent. param newValue the new value of the scroll bar see java.awt.Scrollbar#setValues see java.awt.Scrollbar#getValue see java.awt.Scrollbar#getMinimum see java.awt.Scrollbar#getMaximum // Use setValues so that a consistent policy relating // minimum, maximum, visible amount, and value is enforced. setValues(newValue, visibleAmount, minimum, maximum);
public void	setValueIsAdjusting(boolean b) Sets the valueIsAdjusting property. param b new adjustment-in-progress status see #getValueIsAdjusting since 1.4 boolean oldValue; synchronized (this) { oldValue = isAdjusting; isAdjusting = b; } if ((oldValue != b) && (accessibleContext != null)) { accessibleContext.firePropertyChange( AccessibleContext.ACCESSIBLE_STATE_PROPERTY, ((oldValue) ? AccessibleState.BUSY : null), ((b) ? AccessibleState.BUSY : null)); }
public void	setValues(int value, int visible, int minimum, int maximum) Sets the values of four properties for this scroll bar: value, visibleAmount, minimum, and maximum. If the values supplied for these properties are inconsistent or incorrect, they will be changed to ensure consistency. This method simultaneously and synchronously sets the values of four scroll bar properties, assuring that the values of these properties are mutually consistent. It enforces the following constraints: maximum must be greater than minimum, maximum - minimum must not be greater than Integer.MAX_VALUE, visibleAmount must be greater than zero. visibleAmount must not be greater than maximum - minimum, value must not be less than minimum, and value must not be greater than maximum - visibleAmount Calling this method does not fire an AdjustmentEvent. param value is the position in the current window param visible is the visible amount of the scroll bar param minimum is the minimum value of the scroll bar param maximum is the maximum value of the scroll bar see #setMinimum see #setMaximum see #setVisibleAmount see #setValue int oldValue; synchronized (this) { if (minimum == Integer.MAX_VALUE) { minimum = Integer.MAX_VALUE - 1; } if (maximum <= minimum) { maximum = minimum + 1; } long maxMinusMin = (long) maximum - (long) minimum; if (maxMinusMin > Integer.MAX_VALUE) { maxMinusMin = Integer.MAX_VALUE; maximum = minimum + (int) maxMinusMin; } if (visible > (int) maxMinusMin) { visible = (int) maxMinusMin; } if (visible < 1) { visible = 1; } if (value < minimum) { value = minimum; } if (value > maximum - visible) { value = maximum - visible; } oldValue = this.value; this.value = value; this.visibleAmount = visible; this.minimum = minimum; this.maximum = maximum; ScrollbarPeer peer = (ScrollbarPeer)this.peer; if (peer != null) { peer.setValues(value, visibleAmount, minimum, maximum); } } if ((oldValue != value) && (accessibleContext != null)) { accessibleContext.firePropertyChange( AccessibleContext.ACCESSIBLE_VALUE_PROPERTY, new Integer(oldValue), new Integer(value)); }
public void	setVisibleAmount(int newAmount) Sets the visible amount of this scroll bar. When a scroll bar is used to select a range of values, the visible amount is used to represent the range of values that are currently visible. The size of the scroll bar's bubble (also called a thumb or scroll box), usually gives a visual representation of the relationship of the visible amount to the range of the scroll bar. The scroll bar's bubble may not be displayed when it is not moveable (e.g. when it takes up the entire length of the scroll bar's track, or when the scroll bar is disabled). Whether the bubble is displayed or not will not affect the value returned by getVisibleAmount. If the visible amount supplied is less than one or greater than the current maximum - minimum, then either one or maximum - minimum is substituted, as appropriate. Normally, a program should change a scroll bar's value only by calling setValues. The setValues method simultaneously and synchronously sets the minimum, maximum, visible amount, and value properties of a scroll bar, so that they are mutually consistent. param newAmount the new visible amount see java.awt.Scrollbar#getVisibleAmount see java.awt.Scrollbar#setValues since JDK1.1 // Use setValues so that a consistent policy relating // minimum, maximum, visible amount, and value is enforced. setValues(value, newAmount, minimum, maximum);
private void	writeObject(java.io.ObjectOutputStream s) Writes default serializable fields to stream. Writes a list of serializable AdjustmentListeners as optional data. The non-serializable listeners are detected and no attempt is made to serialize them. param s the ObjectOutputStream to write serialData null terminated sequence of 0 or more pairs; the pair consists of a String and an Object; the String indicates the type of object and is one of the following: adjustmentListenerK indicating an AdjustmentListener object see AWTEventMulticaster#save(ObjectOutputStream, String, EventListener) see java.awt.Component#adjustmentListenerK see #readObject(ObjectInputStream) s.defaultWriteObject(); AWTEventMulticaster.save(s, adjustmentListenerK, adjustmentListener); s.writeObject(null);