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JavaTM 2 Platform Std. Ed. v1.4.2 |
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java.lang.Objectjava.awt.Component
java.awt.Scrollbar
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:
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" or "thumb" can 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 is the visible range of the scroll bar. 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.
In the previous example, because the maximum is
300 and the visible 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 event 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
AdjustmentEvent,
AdjustmentListener,
Serialized Form| Nested Class Summary | |
protected class |
Scrollbar.AccessibleAWTScrollBar
This class implements accessibility support for the Scrollbar class. |
| Nested classes inherited from class java.awt.Component |
Component.AccessibleAWTComponent, Component.BltBufferStrategy, Component.FlipBufferStrategy |
| Field Summary | |
static int |
HORIZONTAL
A constant that indicates a horizontal scroll bar. |
static int |
VERTICAL
A constant that indicates a vertical scroll bar. |
| Fields inherited from class java.awt.Component |
BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT |
| Fields inherited from interface java.awt.Adjustable |
NO_ORIENTATION |
| Fields inherited from interface java.awt.image.ImageObserver |
ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH |
| Constructor Summary | |
Scrollbar()
Constructs a new vertical scroll bar. |
|
Scrollbar(int orientation)
Constructs a new scroll bar with the specified orientation. |
|
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. |
|
| Method Summary | |
void |
addAdjustmentListener(AdjustmentListener l)
Adds the specified adjustment listener to receive instances of AdjustmentEvent from this scroll bar. |
void |
addNotify()
Creates the Scrollbar's peer. |
AccessibleContext |
getAccessibleContext()
Gets the AccessibleContext associated with this
Scrollbar. |
AdjustmentListener[] |
getAdjustmentListeners()
Returns an array of all the adjustment listeners registered on this scrollbar. |
int |
getBlockIncrement()
Gets the block increment of this scroll bar. |
int |
getLineIncrement()
Deprecated. As of JDK version 1.1, replaced by getUnitIncrement(). |
EventListener[] |
getListeners(Class listenerType)
Returns an array of all the objects currently registered as FooListeners
upon this Scrollbar. |
int |
getMaximum()
Gets the maximum value of this scroll bar. |
int |
getMinimum()
Gets the minimum value of this scroll bar. |
int |
getOrientation()
Returns the orientation of this scroll bar. |
int |
getPageIncrement()
Deprecated. As of JDK version 1.1, replaced by getBlockIncrement(). |
int |
getUnitIncrement()
Gets the unit increment for this scrollbar. |
int |
getValue()
Gets the current value of this scroll bar. |
boolean |
getValueIsAdjusting()
Returns true if the value is in the process of changing as a result of actions being taken by the user. |
int |
getVisible()
Deprecated. As of JDK version 1.1, replaced by getVisibleAmount(). |
int |
getVisibleAmount()
Gets the visible amount of this scroll bar. |
protected String |
paramString()
Returns a string representing the state of this Scrollbar. |
protected void |
processAdjustmentEvent(AdjustmentEvent e)
Processes adjustment events occurring on this scrollbar by dispatching them to any registered AdjustmentListener objects. |
protected void |
processEvent(AWTEvent e)
Processes events on this scroll bar. |
void |
removeAdjustmentListener(AdjustmentListener l)
Removes the specified adjustment listener so that it no longer receives instances of AdjustmentEvent from this scroll bar. |
void |
setBlockIncrement(int v)
Sets the block increment for this scroll bar. |
void |
setLineIncrement(int v)
Deprecated. As of JDK version 1.1, replaced by setUnitIncrement(int). |
void |
setMaximum(int newMaximum)
Sets the maximum value of this scroll bar. |
void |
setMinimum(int newMinimum)
Sets the minimum value of this scroll bar. |
void |
setOrientation(int orientation)
Sets the orientation for this scroll bar. |
void |
setPageIncrement(int v)
Deprecated. As of JDK version 1.1, replaced by setBlockIncrement(). |
void |
setUnitIncrement(int v)
Sets the unit increment for this scroll bar. |
void |
setValue(int newValue)
Sets the value of this scroll bar to the specified value. |
void |
setValueIsAdjusting(boolean b)
Sets the valueIsAdjusting property. |
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. |
void |
setVisibleAmount(int newAmount)
Sets the visible amount of this scroll bar. |
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
| Field Detail |
public static final int HORIZONTAL
public static final int VERTICAL
| Constructor Detail |
public Scrollbar()
throws HeadlessException
| Property | Description | Default Value |
|---|---|---|
| orientation | indicates if the scroll bar is vertical or horizontal | Scrollbar.VERTICAL |
| value | value which controls the location
of the scroll bar bubble |
0 |
| 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 |
HeadlessException - if GraphicsEnvironment.isHeadless()
returns true.GraphicsEnvironment.isHeadless()
public Scrollbar(int orientation)
throws HeadlessException
The orientation argument must take one of the two
values Scrollbar.HORIZONTAL,
or Scrollbar.VERTICAL,
indicating a horizontal or vertical scroll bar, respectively.
orientation - indicates the orientation of the scroll bar
IllegalArgumentException - when an illegal value for
the orientation argument is supplied
HeadlessException - if GraphicsEnvironment.isHeadless()
returns true.GraphicsEnvironment.isHeadless()
public Scrollbar(int orientation,
int value,
int visible,
int minimum,
int maximum)
throws HeadlessException
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 setValues(int, int, int, int).
orientation - indicates the orientation of the scroll bar.value - the initial value of the scroll barvisible - the size of the scroll bar's bubble, representing
the visible portion.minimum - the minimum value of the scroll barmaximum - the maximum value of the scroll bar
IllegalArgumentException - when an illegal value for
the orientation argument is supplied
HeadlessException - if GraphicsEnvironment.isHeadless()
returns true.setValues(int, int, int, int),
GraphicsEnvironment.isHeadless()| Method Detail |
public void addNotify()
Scrollbar's peer. The peer allows you to modify
the appearance of the Scrollbar without changing any of its
functionality.
addNotify in class ComponentComponent.isDisplayable(),
Component.removeNotify()public int getOrientation()
getOrientation in interface AdjustableScrollbar.HORIZONTAL or
Scrollbar.VERTICALsetOrientation(int)public void setOrientation(int orientation)
orientation - the orientation of this scroll bar, either
Scrollbar.HORIZONTAL or
Scrollbar.VERTICAL
IllegalArgumentException - if the value supplied
for orientation is not a
legal valuegetOrientation()public int getValue()
getValue in interface AdjustablegetMinimum(),
getMaximum()public void setValue(int newValue)
If the value supplied is less than the current minimum
or greater than the current
maximum - visibleAmount, then one of
those values 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.
setValue in interface AdjustablenewValue - the new value of the scroll barsetValues(int, int, int, int),
getValue(),
getMinimum(),
getMaximum()public int getMinimum()
getMinimum in interface AdjustablegetValue(),
getMaximum()public void setMinimum(int newMinimum)
When setMinimum is called, the limiting argument takes
precedence over the existing scrollbar value.
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.MIN_VALUE
will result in the new minimum value to be set to
Integer.MIN_VALUE - 1.
setMinimum in interface AdjustablenewMinimum - the new minimum value for this scroll barsetValues(int, int, int, int),
setMaximum(int)public int getMaximum()
getMaximum in interface AdjustablegetValue(),
getMinimum()public void setMaximum(int newMaximum)
When setMaximum is called, the limiting
argument takes precedence over the existing scrollbar
value.
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.
setMaximum in interface AdjustablenewMaximum - the new maximum value
for this scroll barsetValues(int, int, int, int),
setMinimum(int)public int getVisibleAmount()
The visible amount of a scroll bar is the range of values represented by the width of the scroll bar's bubble.
getVisibleAmount in interface AdjustablesetVisibleAmount(int)public int getVisible()
getVisibleAmount().
public void setVisibleAmount(int newAmount)
The visible amount of a scroll bar is the range of values represented by the width of the scroll bar's bubble.
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.
setVisibleAmount in interface AdjustablenewAmount - the amount visible per pagegetVisibleAmount(),
setValues(int, int, int, int)public void setUnitIncrement(int v)
The unit increment is the value that is added (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.
setUnitIncrement in interface Adjustablev - the amount by which to increment or decrement
the scroll bar's valuegetUnitIncrement()public void setLineIncrement(int v)
setUnitIncrement(int).
public int getUnitIncrement()
The unit increment is the value that is added (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.
getUnitIncrement in interface AdjustablesetUnitIncrement(int)public int getLineIncrement()
getUnitIncrement().
public void setBlockIncrement(int v)
The block increment is the value that is added (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.
setBlockIncrement in interface Adjustablev - the amount by which to increment or decrement
the scroll bar's valuegetBlockIncrement()public void setPageIncrement(int v)
setBlockIncrement().
public int getBlockIncrement()
The block increment is the value that is added (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.
getBlockIncrement in interface AdjustablesetBlockIncrement(int)public int getPageIncrement()
getBlockIncrement().
public void setValues(int value,
int visible,
int minimum,
int maximum)
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,
visibleAmount must be positive,
visibleAmount must not be greater than
maximum - minimum,
value must not be less than minimum,
and value must not be greater than
maximum - visibleAmount
value - is the position in the current windowvisible - is the amount visible per pageminimum - is the minimum value of the scroll barmaximum - is the maximum value of the scroll barsetMinimum(int),
setMaximum(int),
setVisibleAmount(int),
setValue(int)public boolean getValueIsAdjusting()
valueIsAdjusting propertysetValueIsAdjusting(boolean)public void setValueIsAdjusting(boolean b)
valueIsAdjusting property.
b - new adjustment-in-progress statusgetValueIsAdjusting()public void addAdjustmentListener(AdjustmentListener l)
AdjustmentEvent from this scroll bar.
If l is null, no exception is thrown and no
action is performed.
addAdjustmentListener in interface Adjustablel - the adjustment listenerremoveAdjustmentListener(java.awt.event.AdjustmentListener),
getAdjustmentListeners(),
AdjustmentEvent,
AdjustmentListenerpublic void removeAdjustmentListener(AdjustmentListener l)
AdjustmentEvent from this scroll bar.
If l is null, no exception is thrown and no action
is performed.
removeAdjustmentListener in interface Adjustablel - the adjustment listeneraddAdjustmentListener(java.awt.event.AdjustmentListener),
getAdjustmentListeners(),
AdjustmentEvent,
AdjustmentListenerpublic AdjustmentListener[] getAdjustmentListeners()
AdjustmentListeners
or an empty array if no adjustment
listeners are currently registeredaddAdjustmentListener(java.awt.event.AdjustmentListener),
removeAdjustmentListener(java.awt.event.AdjustmentListener),
AdjustmentEvent,
AdjustmentListenerpublic EventListener[] getListeners(Class listenerType)
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.
getListeners in class ComponentlistenerType - the type of listeners requested; this parameter
should specify an interface that descends from
java.util.EventListener
FooListeners on this component,
or an empty array if no such listeners have been added
ClassCastException - if listenerType
doesn't specify a class or interface that implements
java.util.EventListenerComponent.getComponentListeners(),
Component.getFocusListeners(),
Component.getHierarchyListeners(),
Component.getHierarchyBoundsListeners(),
Component.getKeyListeners(),
Component.getMouseListeners(),
Component.getMouseMotionListeners(),
Component.getMouseWheelListeners(),
Component.getInputMethodListeners(),
Component.getPropertyChangeListeners()protected void processEvent(AWTEvent e)
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.
processEvent in class Componente - the eventAdjustmentEvent,
processAdjustmentEvent(java.awt.event.AdjustmentEvent)protected void processAdjustmentEvent(AdjustmentEvent e)
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.
e - the adjustment eventAdjustmentEvent,
AdjustmentListener,
addAdjustmentListener(java.awt.event.AdjustmentListener),
Component.enableEvents(long)protected String paramString()
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.
paramString in class Componentpublic AccessibleContext getAccessibleContext()
AccessibleContext associated with this
Scrollbar. For scrollbars, the
AccessibleContext takes the form of an
AccessibleAWTScrollBar. A new
AccessibleAWTScrollBar instance is created if necessary.
getAccessibleContext in interface AccessiblegetAccessibleContext in class ComponentAccessibleAWTScrollBar that serves as the
AccessibleContext of this ScrollBar
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JavaTM 2 Platform Std. Ed. v1.4.2 |
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Copyright 2003 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.