* 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:
*
*
*
* 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: *
* 
*
* 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.
*
* @author Sami Shaio
* @see java.awt.event.AdjustmentEvent
* @see java.awt.event.AdjustmentListener
* @since JDK1.0
*/
public class Scrollbar extends Component implements Adjustable, Accessible {
/**
* A constant that indicates a horizontal scroll bar.
*/
public static final int HORIZONTAL = 0;
/**
* A constant that indicates a vertical scroll bar.
*/
public static final int VERTICAL = 1;
/**
* The value of the Scrollbar.
* This property must be greater than or equal to minimum
* and less than or equal to
* maximum - visibleAmount
*
* @serial
* @see #getValue
* @see #setValue
*/
int value;
/**
* The maximum value of the Scrollbar.
* This value must be greater than the minimum
* value.
*
* @serial
* @see #getMaximum
* @see #setMaximum
*/
int maximum;
/**
* The minimum value of the Scrollbar.
* This value must be less than the maximum
* value.
*
* @serial
* @see #getMinimum
* @see #setMinimum
*/
int minimum;
/**
* 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.
* Depending on platform, this may be visually indicated
* by the size of the bubble.
*
* @serial
* @see #getVisibleAmount
* @see #setVisibleAmount
*/
int visibleAmount;
/**
* 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.
*
* @serial
* @see #getOrientation
* @see #setOrientation
*/
int orientation;
/**
* The amount by which the scrollbar value will change when going
* up or down by a line.
* This value must be greater than zero.
*
* @serial
* @see #getLineIncrement
* @see #setLineIncrement
*/
int lineIncrement = 1;
/**
* The amount by which the scrollbar value will change when going
* up or down by a page.
* This value must be greater than zero.
*
* @serial
* @see #getPageIncrement
* @see #setPageIncrement
*/
int pageIncrement = 10;
/**
* 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.
*
* @see #getValueIsAdjusting
* @see #setValueIsAdjusting
* @since 1.4
*/
transient boolean isAdjusting;
transient AdjustmentListener adjustmentListener;
private static final String base = "scrollbar";
private static int nameCounter = 0;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = 8451667562882310543L;
/**
* Initialize JNI field and method IDs.
*/
private static native void initIDs();
static {
/* ensure that the necessary native libraries are loaded */
Toolkit.loadLibraries();
if (!GraphicsEnvironment.isHeadless()) {
initIDs();
}
}
/**
* 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 | *
* 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
*/
public Scrollbar(int orientation) throws HeadlessException {
this(orientation, 0, 10, 0, 100);
}
/**
* 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
*/
public Scrollbar(int orientation, int value, int visible, int minimum,
int maximum) throws HeadlessException {
GraphicsEnvironment.checkHeadless();
switch (orientation) {
case HORIZONTAL:
case VERTICAL:
this.orientation = orientation;
break;
default:
throw new IllegalArgumentException("illegal scrollbar orientation");
}
setValues(value, visible, minimum, maximum);
}
/**
* Constructs a name for this component. Called by getName
* when the name is null.
*/
String constructComponentName() {
synchronized (Scrollbar.class) {
return base + nameCounter++;
}
}
/**
* Creates the Scrollbar's peer. The peer allows you to modify
* the appearance of the Scrollbar without changing any of its
* functionality.
*/
public void addNotify() {
synchronized (getTreeLock()) {
if (peer == null)
peer = getToolkit().createScrollbar(this);
super.addNotify();
}
}
/**
* 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
*/
public int getOrientation() {
return 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
*/
public void setOrientation(int orientation) {
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));
}
}
/**
* 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
*/
public int getValue() {
return value;
}
/**
* 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
*/
public void setValue(int newValue) {
// Use setValues so that a consistent policy relating
// minimum, maximum, visible amount, and value is enforced.
setValues(newValue, visibleAmount, minimum, maximum);
}
/**
* 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
*/
public int getMinimum() {
return minimum;
}
/**
* 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
*/
public void setMinimum(int newMinimum) {
// 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);
}
/**
* 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
*/
public int getMaximum() {
return maximum;
}
/**
* 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
*/
public void setMaximum(int newMaximum) {
// 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);
}
/**
* 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. * Note that depending on platform, the value of the visible amount property * may not be visually indicated by the size of the bubble. *
* 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
*/
public int getVisibleAmount() {
return getVisible();
}
/**
* @deprecated As of JDK version 1.1,
* replaced by getVisibleAmount().
*/
@Deprecated
public int getVisible() {
return visibleAmount;
}
/**
* 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. * Note that depending on platform, the value of the visible amount property * may not be visually indicated by the size of the bubble. *
* 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
*/
public void setVisibleAmount(int newAmount) {
// Use setValues so that a consistent policy relating
// minimum, maximum, visible amount, and value is enforced.
setValues(value, newAmount, minimum, maximum);
}
/**
* 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
*/
public void setUnitIncrement(int v) {
setLineIncrement(v);
}
/**
* @deprecated As of JDK version 1.1,
* replaced by setUnitIncrement(int).
*/
@Deprecated
public synchronized void setLineIncrement(int v) {
int tmp = (v < 1) ? 1 : v;
if (lineIncrement == tmp) {
return;
}
lineIncrement = tmp;
ScrollbarPeer peer = (ScrollbarPeer)this.peer;
if (peer != null) {
peer.setLineIncrement(lineIncrement);
}
}
/**
* 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
*/
public int getUnitIncrement() {
return getLineIncrement();
}
/**
* @deprecated As of JDK version 1.1,
* replaced by getUnitIncrement().
*/
@Deprecated
public int getLineIncrement() {
return lineIncrement;
}
/**
* 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
*/
public void setBlockIncrement(int v) {
setPageIncrement(v);
}
/**
* @deprecated As of JDK version 1.1,
* replaced by setBlockIncrement().
*/
@Deprecated
public synchronized void setPageIncrement(int v) {
int tmp = (v < 1) ? 1 : v;
if (pageIncrement == tmp) {
return;
}
pageIncrement = tmp;
ScrollbarPeer peer = (ScrollbarPeer)this.peer;
if (peer != null) {
peer.setPageIncrement(pageIncrement);
}
}
/**
* 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
*/
public int getBlockIncrement() {
return getPageIncrement();
}
/**
* @deprecated As of JDK version 1.1,
* replaced by getBlockIncrement().
*/
@Deprecated
public int getPageIncrement() {
return pageIncrement;
}
/**
* 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
*/
public void setValues(int value, int visible, int minimum, int maximum) {
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,
Integer.valueOf(oldValue),
Integer.valueOf(value));
}
}
/**
* 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
*/
public boolean getValueIsAdjusting() {
return isAdjusting;
}
/**
* Sets the valueIsAdjusting property.
*
* @param b new adjustment-in-progress status
* @see #getValueIsAdjusting
* @since 1.4
*/
public void setValueIsAdjusting(boolean b) {
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));
}
}
/**
* 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.
*
Refer to AWT Threading Issues for details on AWT's threading model.
*
* @param l the adjustment listener
* @see #removeAdjustmentListener
* @see #getAdjustmentListeners
* @see java.awt.event.AdjustmentEvent
* @see java.awt.event.AdjustmentListener
* @since JDK1.1
*/
public synchronized void addAdjustmentListener(AdjustmentListener l) {
if (l == null) {
return;
}
adjustmentListener = AWTEventMulticaster.add(adjustmentListener, l);
newEventsOnly = true;
}
/**
* 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.
*
Refer to AWT Threading Issues for details on AWT's threading model.
*
* @param l the adjustment listener
* @see #addAdjustmentListener
* @see #getAdjustmentListeners
* @see java.awt.event.AdjustmentEvent
* @see java.awt.event.AdjustmentListener
* @since JDK1.1
*/
public synchronized void removeAdjustmentListener(AdjustmentListener l) {
if (l == null) {
return;
}
adjustmentListener = AWTEventMulticaster.remove(adjustmentListener, l);
}
/**
* 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
*/
public synchronized AdjustmentListener[] getAdjustmentListeners() {
return (AdjustmentListener[])(getListeners(AdjustmentListener.class));
}
/**
* 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
*/
public 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
*/
protected void processEvent(AWTEvent e) {
if (e instanceof AdjustmentEvent) {
processAdjustmentEvent((AdjustmentEvent)e);
return;
}
super.processEvent(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: *
AdjustmentListener object is registered
* via addAdjustmentListener.
* 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
*/
protected void processAdjustmentEvent(AdjustmentEvent e) {
AdjustmentListener listener = adjustmentListener;
if (listener != null) {
listener.adjustmentValueChanged(e);
}
}
/**
* 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
*/
protected String paramString() {
return super.paramString() +
",val=" + value +
",vis=" + visibleAmount +
",min=" + minimum +
",max=" + maximum +
((orientation == VERTICAL) ? ",vert" : ",horz") +
",isAdjusting=" + isAdjusting;
}
/* Serialization support.
*/
/**
* The scroll bar's serialized Data Version.
*
* @serial
*/
private int scrollbarSerializedDataVersion = 1;
/**
* 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)
*/
private void writeObject(ObjectOutputStream s)
throws IOException
{
s.defaultWriteObject();
AWTEventMulticaster.save(s, adjustmentListenerK, adjustmentListener);
s.writeObject(null);
}
/**
* 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)
*/
private void readObject(ObjectInputStream s)
throws ClassNotFoundException, IOException, HeadlessException
{
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();
}
}
/////////////////
// Accessibility support
////////////////
/**
* 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
* @since 1.3
*/
public AccessibleContext getAccessibleContext() {
if (accessibleContext == null) {
accessibleContext = new AccessibleAWTScrollBar();
}
return accessibleContext;
}
/**
* This class implements accessibility support for the
* Scrollbar class. It provides an implementation of
* the Java Accessibility API appropriate to scrollbar
* user-interface elements.
* @since 1.3
*/
protected class AccessibleAWTScrollBar extends AccessibleAWTComponent
implements AccessibleValue
{
/*
* JDK 1.3 serialVersionUID
*/
private static final long serialVersionUID = -344337268523697807L;
/**
* Get the state set of this object.
*
* @return an instance of AccessibleState
* containing the current state of the object
* @see AccessibleState
*/
public AccessibleStateSet getAccessibleStateSet() {
AccessibleStateSet states = super.getAccessibleStateSet();
if (getValueIsAdjusting()) {
states.add(AccessibleState.BUSY);
}
if (getOrientation() == VERTICAL) {
states.add(AccessibleState.VERTICAL);
} else {
states.add(AccessibleState.HORIZONTAL);
}
return states;
}
/**
* Get the role of this object.
*
* @return an instance of AccessibleRole
* describing the role of the object
*/
public AccessibleRole getAccessibleRole() {
return AccessibleRole.SCROLL_BAR;
}
/**
* Get the AccessibleValue associated with this
* object. In the implementation of the Java Accessibility
* API for this class, return this object, which is
* responsible for implementing the
* AccessibleValue interface on behalf of itself.
*
* @return this object
*/
public AccessibleValue getAccessibleValue() {
return this;
}
/**
* Get the accessible value of this object.
*
* @return The current value of this object.
*/
public Number getCurrentAccessibleValue() {
return Integer.valueOf(getValue());
}
/**
* Set the value of this object as a Number.
*
* @return True if the value was set.
*/
public boolean setCurrentAccessibleValue(Number n) {
if (n instanceof Integer) {
setValue(n.intValue());
return true;
} else {
return false;
}
}
/**
* Get the minimum accessible value of this object.
*
* @return The minimum value of this object.
*/
public Number getMinimumAccessibleValue() {
return Integer.valueOf(getMinimum());
}
/**
* Get the maximum accessible value of this object.
*
* @return The maximum value of this object.
*/
public Number getMaximumAccessibleValue() {
return Integer.valueOf(getMaximum());
}
} // AccessibleAWTScrollBar
}