FileDocCategorySizeDatePackage
Scrollbar.javaAPI DocJava SE 5 API46115Fri Aug 26 14:56:46 BST 2005java.awt

Scrollbar

public class Scrollbar extends Component implements Adjustable, Accessible
The Scrollbar class embodies a scroll bar, a familiar user-interface object. A scroll bar provides a convenient means for allowing a user to select from a range of values. The following three vertical scroll bars could be used as slider controls to pick the red, green, and blue components of a color:

Image shows 3 vertical sliders, side-by-side.

Each scroll bar in this example could be created with code similar to the following:


redSlider=new Scrollbar(Scrollbar.VERTICAL, 0, 1, 0, 255);
add(redSlider);

Alternatively, a scroll bar can represent a range of values. For example, if a scroll bar is used for scrolling through text, the width of the "bubble" (also called the "thumb" or "scroll box") can be used to represent the amount of text that is visible. Here is an example of a scroll bar that represents a range:

Image shows horizontal slider with starting range of 0 and ending range of 300. The slider thumb is labeled 60.

The value range represented by the bubble in this example is the visible amount. The horizontal scroll bar in this example could be created with code like the following:


ranger = new Scrollbar(Scrollbar.HORIZONTAL, 0, 60, 0, 300);
add(ranger);

Note that the actual maximum value of the scroll bar is the maximum minus the visible amount. In the previous example, because the maximum is 300 and the visible amount is 60, the actual maximum value is 240. The range of the scrollbar track is 0 - 300. The left side of the bubble indicates the value of the scroll bar.

Normally, the user changes the value of the scroll bar by making a gesture with the mouse. For example, the user can drag the scroll bar's bubble up and down, or click in the scroll bar's unit increment or block increment areas. Keyboard gestures can also be mapped to the scroll bar. By convention, the Page Up and Page Down keys are equivalent to clicking in the scroll bar's block increment and block decrement areas.

When the user changes the value of the scroll bar, the scroll bar receives an instance of AdjustmentEvent. The scroll bar processes this event, passing it along to any registered listeners.

Any object that wishes to be notified of changes to the scroll bar's value should implement AdjustmentListener, an interface defined in the package java.awt.event. Listeners can be added and removed dynamically by calling the methods addAdjustmentListener and removeAdjustmentListener.

The AdjustmentEvent class defines five types of adjustment event, listed here:

  • AdjustmentEvent.TRACK is sent out when the user drags the scroll bar's bubble.
  • AdjustmentEvent.UNIT_INCREMENT is sent out when the user clicks in the left arrow of a horizontal scroll bar, or the top arrow of a vertical scroll bar, or makes the equivalent gesture from the keyboard.
  • AdjustmentEvent.UNIT_DECREMENT is sent out when the user clicks in the right arrow of a horizontal scroll bar, or the bottom arrow of a vertical scroll bar, or makes the equivalent gesture from the keyboard.
  • AdjustmentEvent.BLOCK_INCREMENT is sent out when the user clicks in the track, to the left of the bubble on a horizontal scroll bar, or above the bubble on a vertical scroll bar. By convention, the Page Up key is equivalent, if the user is using a keyboard that defines a Page Up key.
  • AdjustmentEvent.BLOCK_DECREMENT is sent out when the user clicks in the track, to the right of the bubble on a horizontal scroll bar, or below the bubble on a vertical scroll bar. By convention, the Page Down key is equivalent, if the user is using a keyboard that defines a Page Down key.

The JDK 1.0 event system is supported for backwards compatibility, but its use with newer versions of the platform is discouraged. The five types of adjustment events introduced with JDK 1.1 correspond to the five event types that are associated with scroll bars in previous platform versions. The following list gives the adjustment event type, and the corresponding JDK 1.0 event type it replaces.

  • AdjustmentEvent.TRACK replaces Event.SCROLL_ABSOLUTE
  • AdjustmentEvent.UNIT_INCREMENT replaces Event.SCROLL_LINE_UP
  • AdjustmentEvent.UNIT_DECREMENT replaces Event.SCROLL_LINE_DOWN
  • AdjustmentEvent.BLOCK_INCREMENT replaces Event.SCROLL_PAGE_UP
  • AdjustmentEvent.BLOCK_DECREMENT replaces Event.SCROLL_PAGE_DOWN

Note: We recommend using a Scrollbar for value selection only. If you want to implement a scrollable component inside a container, we recommend you use a {@link ScrollPane ScrollPane}. If you use a Scrollbar for this purpose, you are likely to encounter issues with painting, key handling, sizing and positioning.

version
1.108, 05/18/04
author
Sami Shaio
see
java.awt.event.AdjustmentEvent
see
java.awt.event.AdjustmentListener
since
JDK1.0

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 voidaddAdjustmentListener(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 voidaddNotify()
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.StringconstructComponentName()
Constructs a name for this component. Called by getName when the name is null.

        synchronized (getClass()) {
	    return base + nameCounter++;
	}
    
booleaneventEnabled(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.AccessibleContextgetAccessibleContext()
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 intgetBlockIncrement()
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 intgetLineIncrement()

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 intgetMaximum()
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 intgetMinimum()
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 intgetOrientation()
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 intgetPageIncrement()

deprecated
As of JDK version 1.1, replaced by getBlockIncrement().

	return pageIncrement;
    
public intgetUnitIncrement()
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 intgetValue()
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 booleangetValueIsAdjusting()
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 intgetVisible()

deprecated
As of JDK version 1.1, replaced by getVisibleAmount().

	return visibleAmount;
    
public intgetVisibleAmount()
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 voidinitIDs()
Initialize JNI field and method IDs.

protected java.lang.StringparamString()
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 voidprocessAdjustmentEvent(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 voidprocessEvent(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 voidreadObject(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 voidremoveAdjustmentListener(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 voidsetBlockIncrement(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 voidsetLineIncrement(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 voidsetMaximum(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 voidsetMinimum(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 voidsetOrientation(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 voidsetPageIncrement(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 voidsetUnitIncrement(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 voidsetValue(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 voidsetValueIsAdjusting(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 voidsetValues(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 voidsetVisibleAmount(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 voidwriteObject(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);