javax.swing
Class JScrollBar

java.lang.Object
  java.awt.Component
      java.awt.Container
          javax.swing.JComponent
              javax.swing.JScrollBar

All Implemented Interfaces:

java.awt.Adjustable, java.awt.image.ImageObserver, java.io.Serializable

Direct Known Subclasses:

JScrollPane.ScrollBar

public class JScrollBar

extends JComponent

implements java.awt.Adjustable

An implementation of a scrollbar. The user positions the knob in the scrollbar to determine the contents of the viewing area. The program typically adjusts the display so that the end of the scrollbar represents the end of the displayable contents, or 100% of the contents. The start of the scrollbar is the beginning of the displayable contents, or 0%. The position of the knob within those bounds then translates to the corresponding percentage of the displayable contents.

Typically, as the position of the knob in the scrollbar changes a corresponding change is made to the position of the JViewport on the underlying view, changing the contents of the JViewport.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans^TM has been added to the java.beans package. Please see java.beans.XMLEncoder.

See Also:

JScrollPane

Field Summary

protected int	blockIncrement
protected BoundedRangeModel	model The model that represents the scrollbar's minimum, maximum, extent (aka "visibleAmount") and current value.
protected int	orientation
protected int	unitIncrement

Fields inherited from class javax.swing.JComponent

listenerList, TOOL_TIP_TEXT_KEY, UNDEFINED_CONDITION, WHEN_ANCESTOR_OF_FOCUSED_COMPONENT, WHEN_FOCUSED, WHEN_IN_FOCUSED_WINDOW

Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Fields inherited from interface java.awt.Adjustable

HORIZONTAL, NO_ORIENTATION, VERTICAL

Fields inherited from interface java.awt.image.ImageObserver

ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH

Constructor Summary

JScrollBar()
Creates a vertical scrollbar with the following initial values:

JScrollBar(int orientation)
Creates a scrollbar with the specified orientation and the following initial values:

JScrollBar(int orientation, int value, int extent, int min, int max)
Creates a scrollbar with the specified orientation, value, extent, minimum, and maximum.

Method Summary

void	addAdjustmentListener(java.awt.event.AdjustmentListener l) Adds an AdjustmentListener.
protected void	fireAdjustmentValueChanged(int id, int type, int value)
java.awt.event.AdjustmentListener[]	getAdjustmentListeners() Returns an array of all the AdjustmentListeners added to this JScrollBar with addAdjustmentListener().
int	getBlockIncrement() For backwards compatibility with java.awt.Scrollbar.
int	getBlockIncrement(int direction) Returns the amount to change the scrollbar's value by, given a block (usually "page") up/down request.
int	getMaximum() The maximum value of the scrollbar is maximum - extent.
Dimension	getMaximumSize() The scrollbar is flexible along it's scrolling axis and rigid along the other axis.
int	getMinimum() Returns the minimum value supported by the scrollbar (usually zero).
Dimension	getMinimumSize() The scrollbar is flexible along it's scrolling axis and rigid along the other axis.
BoundedRangeModel	getModel() Returns data model that handles the scrollbar's four fundamental properties: minimum, maximum, value, extent.
int	getOrientation() Returns the component's orientation (horizontal or vertical).
int	getUnitIncrement() For backwards compatibility with java.awt.Scrollbar.
int	getUnitIncrement(int direction) Returns the amount to change the scrollbar's value by, given a unit up/down request.
int	getValue() Returns the scrollbar's value.
boolean	getValueIsAdjusting() True if the scrollbar knob is being dragged.
int	getVisibleAmount() Returns the scrollbar's extent, aka its "visibleAmount".
void	paint(java.awt.Graphics g) Invoked by Swing to draw components.
protected void	paintBorder(java.awt.Graphics g) Paints the component's border.
protected void	paintComponent(java.awt.Graphics g) Calls the UI delegate's paint method, if the UI delegate is non-null.
void	paintComponents(java.awt.Graphics g)
protected java.lang.String	paramString() Returns a string representation of this JScrollBar.
protected void	printBorder(java.awt.Graphics g) Prints the component's border.
protected void	printComponent(java.awt.Graphics g) This is invoked during a printing operation.
void	printComponents(java.awt.Graphics g)
void	removeAdjustmentListener(java.awt.event.AdjustmentListener l) Removes an AdjustmentEvent listener.
void	setBlockIncrement(int blockIncrement) Sets the blockIncrement property.
void	setEnabled(boolean x) Enables the component so that the knob position can be changed.
void	setMaximum(int maximum) Sets the model's maximum property.
void	setMinimum(int minimum) Sets the model's minimum property.
void	setModel(BoundedRangeModel newModel) Sets the model that handles the scrollbar's four fundamental properties: minimum, maximum, value, extent.
void	setOrientation(int orientation) Set the scrollbar's orientation to either VERTICAL or HORIZONTAL.
void	setUnitIncrement(int unitIncrement) Sets the unitIncrement property.
void	setValue(int value) Sets the scrollbar's value.
void	setValueIsAdjusting(boolean b) Sets the model's valueIsAdjusting property.
void	setValues(int newValue, int newExtent, int newMin, int newMax) Sets the four BoundedRangeModel properties after forcing the arguments to obey the usual constraints:
void	setVisibleAmount(int extent) Set the model's extent property.

Methods inherited from class javax.swing.JComponent

addAncestorListener, addNotify, addPropertyChangeListener, addPropertyChangeListener, addVetoableChangeListener, computeVisibleRect, contains, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getActionMap, getAlignmentX, getAlignmentY, getAncestorListeners, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getConditionForKeyStroke, getDefaultLocale, getGraphics, getHeight, getInputMap, getInputMap, getInputVerifier, getInsets, getInsets, getListeners, getLocation, getPreferredSize, getPropertyChangeListeners, getPropertyChangeListeners, getRegisteredKeyStrokes, getSize, getToolTipText, getVerifyInputWhenFocusTarget, getVetoableChangeListeners, getVisibleRect, getWidth, getX, getY, isDoubleBuffered, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isOptimizedDrawingEnabled, isPaintingTile, isPreferredSizeSet, isRequestFocusEnabled, isValidateRoot, paintChildren, paintImmediately, paintImmediately, print, printAll, printChildren, processComponentKeyEvent, processKeyBinding, processKeyEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, removeVetoableChangeListener, repaint, repaint, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setActionMap, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setBorder, setDefaultLocale, setDoubleBuffered, setFont, setForeground, setInputMap, setInputVerifier, setMaximumSize, setMinimumSize, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setVerifyInputWhenFocusTarget, setVisible, unregisterKeyboardAction, update

Methods inherited from class java.awt.Container

add, add, add, add, add, addContainerListener, addImpl, areFocusTraversalKeysSet, doLayout, findComponentAt, findComponentAt, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getContainerListeners, getFocusTraversalKeys, getFocusTraversalPolicy, getLayout, invalidate, isAncestorOf, isFocusCycleRoot, isFocusCycleRoot, isFocusTraversalPolicySet, list, list, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, setFocusCycleRoot, setFocusTraversalKeys, setFocusTraversalPolicy, setLayout, transferFocusBackward, transferFocusDownCycle, validate, validateTree

Methods inherited from class java.awt.Component

addComponentListener, addFocusListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, checkImage, checkImage, coalesceEvents, contains, createImage, createImage, createVolatileImage, createVolatileImage, disableEvents, dispatchEvent, enableEvents, enableInputMethods, getBackground, getBounds, getColorModel, getComponentListeners, getCursor, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphicsConfiguration, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocale, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMouseWheelListeners, getName, getParent, getSize, getToolkit, getTreeLock, hasFocus, imageUpdate, isBackgroundSet, isCursorSet, isDisplayable, isEnabled, isFocusable, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isShowing, isValid, isVisible, list, list, list, paintAll, prepareImage, prepareImage, processComponentEvent, processFocusEvent, processInputMethodEvent, processMouseEvent, processMouseWheelEvent, removeComponentListener, removeFocusListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, repaint, repaint, repaint, setBounds, setBounds, setCursor, setFocusable, setFocusTraversalKeysEnabled, setIgnoreRepaint, setLocale, setLocation, setLocation, setName, setSize, setSize, toString, transferFocus, transferFocusUpCycle

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

model

protected BoundedRangeModel model

The model that represents the scrollbar's minimum, maximum, extent (aka "visibleAmount") and current value.

See Also:

setModel(javax.swing.BoundedRangeModel)

orientation

protected int orientation

See Also:

setOrientation(int)

unitIncrement

protected int unitIncrement

See Also:

setUnitIncrement(int)

blockIncrement

protected int blockIncrement

See Also:

setBlockIncrement(int)

Constructor Detail

JScrollBar

public JScrollBar(int orientation,
                  int value,
                  int extent,
                  int min,
                  int max)

Creates a scrollbar with the specified orientation, value, extent, minimum, and maximum. The "extent" is the size of the viewable area. It is also known as the "visible amount".

Note: Use setBlockIncrement to set the block increment to a size slightly smaller than the view's extent. That way, when the user jumps the knob to an adjacent position, one or two lines of the original contents remain in view.

Throws:

java.lang.IllegalArgumentException - if orientation is not one of VERTICAL, HORIZONTAL

See Also:

setOrientation(int), setValue(int), setVisibleAmount(int), setMinimum(int), setMaximum(int)

JScrollBar

public JScrollBar(int orientation)

Creates a scrollbar with the specified orientation and the following initial values:

 minimum = 0 
 maximum = 100 
 value = 0
 extent = 10
 

JScrollBar

public JScrollBar()

Creates a vertical scrollbar with the following initial values:

 minimum = 0 
 maximum = 100 
 value = 0
 extent = 10
 

Method Detail

paint

public final void paint(java.awt.Graphics g)

Description copied from class: JComponent

Invoked by Swing to draw components. Applications should not invoke paint directly, but should instead use the repaint method to schedule the component for redrawing.

This method actually delegates the work of painting to three protected methods: paintComponent, paintBorder, and paintChildren. They're called in the order listed to ensure that children appear on top of component itself. Generally speaking, the component and its children should not paint in the insets area allocated to the border. Subclasses can just override this method, as always.

Overrides:

paint in class JComponent

Parameters:

g - the Graphics context in which to paint

See Also:

JComponent.paintBorder(java.awt.Graphics), JComponent.paintChildren(java.awt.Graphics), JComponent.getComponentGraphics(java.awt.Graphics), JComponent.repaint(long, int, int, int, int)

getOrientation

public int getOrientation()

Returns the component's orientation (horizontal or vertical).

Specified by:

getOrientation in interface java.awt.Adjustable

Returns:

VERTICAL or HORIZONTAL

See Also:

setOrientation(int), Adjustable.getOrientation()

setOrientation

public void setOrientation(int orientation)

Set the scrollbar's orientation to either VERTICAL or HORIZONTAL.

Throws:

java.lang.IllegalArgumentException - if orientation is not one of VERTICAL, HORIZONTAL

See Also:

getOrientation()

getModel

public BoundedRangeModel getModel()

Returns data model that handles the scrollbar's four fundamental properties: minimum, maximum, value, extent.

See Also:

setModel(javax.swing.BoundedRangeModel)

setModel

public void setModel(BoundedRangeModel newModel)

Sets the model that handles the scrollbar's four fundamental properties: minimum, maximum, value, extent.

See Also:

getModel()

getUnitIncrement

public int getUnitIncrement(int direction)

Returns the amount to change the scrollbar's value by, given a unit up/down request. A ScrollBarUI implementation typically calls this method when the user clicks on a scrollbar up/down arrow and uses the result to update the scrollbar's value. Subclasses my override this method to compute a value, e.g. the change required to scroll up or down one (variable height) line text or one row in a table.

The JScrollPane component creates scrollbars (by default) that override this method and delegate to the viewports Scrollable view, if it has one. The Scrollable interface provides a more specialized version of this method.

Parameters:

direction - is -1 or 1 for up/down respectively

Returns:

the value of the unitIncrement property

See Also:

setUnitIncrement(int), setValue(int), Scrollable.getScrollableUnitIncrement(java.awt.Rectangle, int, int)

setUnitIncrement

public void setUnitIncrement(int unitIncrement)

Sets the unitIncrement property.

Specified by:

setUnitIncrement in interface java.awt.Adjustable

See Also:

getUnitIncrement(int)

getBlockIncrement

public int getBlockIncrement(int direction)

Returns the amount to change the scrollbar's value by, given a block (usually "page") up/down request. A ScrollBarUI implementation typically calls this method when the user clicks above or below the scrollbar "knob" to change the value up or down by large amount. Subclasses my override this method to compute a value, e.g. the change required to scroll up or down one paragraph in a text document.

The JScrollPane component creates scrollbars (by default) that override this method and delegate to the viewports Scrollable view, if it has one. The Scrollable interface provides a more specialized version of this method.

Parameters:

direction - is -1 or 1 for up/down respectively

Returns:

the value of the blockIncrement property

See Also:

setBlockIncrement(int), setValue(int), Scrollable.getScrollableBlockIncrement(java.awt.Rectangle, int, int)

setBlockIncrement

public void setBlockIncrement(int blockIncrement)

Sets the blockIncrement property.

Specified by:

setBlockIncrement in interface java.awt.Adjustable

See Also:

getBlockIncrement()

getUnitIncrement

public int getUnitIncrement()

For backwards compatibility with java.awt.Scrollbar.

Specified by:

getUnitIncrement in interface java.awt.Adjustable

See Also:

Adjustable.getUnitIncrement(), getUnitIncrement(int)

getBlockIncrement

public int getBlockIncrement()

For backwards compatibility with java.awt.Scrollbar.

Specified by:

getBlockIncrement in interface java.awt.Adjustable

See Also:

Adjustable.getBlockIncrement(), getBlockIncrement(int)

getValue

public int getValue()

Returns the scrollbar's value.

Specified by:

getValue in interface java.awt.Adjustable

Returns:

the model's value property

See Also:

setValue(int)

setValue

public void setValue(int value)

Sets the scrollbar's value. This method just forwards the value to the model.

Specified by:

setValue in interface java.awt.Adjustable

See Also:

getValue(), BoundedRangeModel.setValue(int)

getVisibleAmount

public int getVisibleAmount()

Returns the scrollbar's extent, aka its "visibleAmount". In many scrollbar look and feel implementations the size of the scrollbar "knob" or "thumb" is proportional to the extent.

Specified by:

getVisibleAmount in interface java.awt.Adjustable

Returns:

the value of the model's extent property

See Also:

setVisibleAmount(int)

setVisibleAmount

public void setVisibleAmount(int extent)

Set the model's extent property.

Specified by:

setVisibleAmount in interface java.awt.Adjustable

See Also:

getVisibleAmount(), BoundedRangeModel.setExtent(int)

getMinimum

public int getMinimum()

Returns the minimum value supported by the scrollbar (usually zero).

Specified by:

getMinimum in interface java.awt.Adjustable

Returns:

the value of the model's minimum property

See Also:

setMinimum(int)

setMinimum

public void setMinimum(int minimum)

Sets the model's minimum property.

Specified by:

setMinimum in interface java.awt.Adjustable

See Also:

getMinimum(), BoundedRangeModel.setMinimum(int)

getMaximum

public int getMaximum()

The maximum value of the scrollbar is maximum - extent.

Specified by:

getMaximum in interface java.awt.Adjustable

Returns:

the value of the model's maximum property

See Also:

setMaximum(int)

setMaximum

public void setMaximum(int maximum)

Sets the model's maximum property. Note that the scrollbar's value can only be set to maximum - extent.

Specified by:

setMaximum in interface java.awt.Adjustable

See Also:

getMaximum(), BoundedRangeModel.setMaximum(int)

getValueIsAdjusting

public boolean getValueIsAdjusting()

True if the scrollbar knob is being dragged.

Returns:

the value of the model's valueIsAdjusting property

See Also:

setValueIsAdjusting(boolean)

setValueIsAdjusting

public void setValueIsAdjusting(boolean b)

Sets the model's valueIsAdjusting property. Scrollbar look and feel implementations should set this property to true when a knob drag begins, and to false when the drag ends. The scrollbar model will not generate ChangeEvents while valueIsAdjusting is true.

See Also:

getValueIsAdjusting(), BoundedRangeModel.setValueIsAdjusting(boolean)

setValues

public void setValues(int newValue,
                      int newExtent,
                      int newMin,
                      int newMax)

Sets the four BoundedRangeModel properties after forcing the arguments to obey the usual constraints:

 minimum <= value <= value+extent <= maximum
 

See Also:

BoundedRangeModel.setRangeProperties(int, int, int, int, boolean), setValue(int), setVisibleAmount(int), setMinimum(int), setMaximum(int)

addAdjustmentListener

public void addAdjustmentListener(java.awt.event.AdjustmentListener l)

Adds an AdjustmentListener. Adjustment listeners are notified each time the scrollbar's model changes. Adjustment events are provided for backwards compatibility with java.awt.Scrollbar.

Note that the AdjustmentEvents type property will always have a placeholder value of AdjustmentEvent.TRACK because all changes to a BoundedRangeModels value are considered equivalent. To change the value of a BoundedRangeModel one just sets its value property, i.e. model.setValue(123). No information about the origin of the change, e.g. it's a block decrement, is provided. We don't try fabricate the origin of the change here.

Specified by:

addAdjustmentListener in interface java.awt.Adjustable

Parameters:

l - the AdjustmentLister to add

See Also:

removeAdjustmentListener(java.awt.event.AdjustmentListener), BoundedRangeModel.addChangeListener(javax.swing.event.ChangeListener)

removeAdjustmentListener

public void removeAdjustmentListener(java.awt.event.AdjustmentListener l)

Removes an AdjustmentEvent listener.

Specified by:

removeAdjustmentListener in interface java.awt.Adjustable

Parameters:

l - the AdjustmentLister to remove

See Also:

addAdjustmentListener(java.awt.event.AdjustmentListener)

getAdjustmentListeners

public java.awt.event.AdjustmentListener[] getAdjustmentListeners()

Returns an array of all the AdjustmentListeners added to this JScrollBar with addAdjustmentListener().

Returns:

all of the AdjustmentListeners added or an empty array if no listeners have been added

Since:

1.4

fireAdjustmentValueChanged

protected void fireAdjustmentValueChanged(int id,
                                          int type,
                                          int value)

getMinimumSize

public Dimension getMinimumSize()

The scrollbar is flexible along it's scrolling axis and rigid along the other axis.

Overrides:

getMinimumSize in class JComponent

Returns:

the value of the minimumSize property

See Also:

JComponent.setMinimumSize(java.awt.Dimension), ComponentUI

getMaximumSize

public Dimension getMaximumSize()

The scrollbar is flexible along it's scrolling axis and rigid along the other axis.

Overrides:

getMaximumSize in class JComponent

Returns:

the value of the maximumSize property

See Also:

JComponent.setMaximumSize(java.awt.Dimension), ComponentUI

setEnabled

public void setEnabled(boolean x)

Enables the component so that the knob position can be changed. When the disabled, the knob position cannot be changed.

Overrides:

setEnabled in class JComponent

Parameters:

x - a boolean value, where true enables the component and false disables it

See Also:

Component.isEnabled(), Component.isLightweight()

paramString

protected java.lang.String paramString()

Returns a string representation of this JScrollBar. 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.

Overrides:

paramString in class JComponent

Returns:

a string representation of this JScrollBar.

paintComponent

protected final void paintComponent(java.awt.Graphics g)

Description copied from class: JComponent

Calls the UI delegate's paint method, if the UI delegate is non-null. We pass the delegate a copy of the Graphics object to protect the rest of the paint code from irrevocable changes (for example, Graphics.translate).

Overrides:

paintComponent in class JComponent

Parameters:

g - the Graphics object to protect

See Also:

JComponent.paint(java.awt.Graphics), ComponentUI

paintBorder

protected final void paintBorder(java.awt.Graphics g)

Description copied from class: JComponent

Paints the component's border.

Overrides:

paintBorder in class JComponent

Parameters:

g - the Graphics context in which to paint

See Also:

JComponent.paint(java.awt.Graphics), JComponent.setBorder(javax.swing.border.Border)

paintComponents

public final void paintComponents(java.awt.Graphics g)

printComponent

protected final void printComponent(java.awt.Graphics g)

Description copied from class: JComponent

This is invoked during a printing operation. This is implemented to invoke paintComponent on the component.

Overrides:

printComponent in class JComponent

Parameters:

g - the Graphics context in which to paint

See Also:

JComponent.print(java.awt.Graphics)

printBorder

protected final void printBorder(java.awt.Graphics g)

Description copied from class: JComponent

Prints the component's border. This is implemented to invoke paintBorder on the component.

Overrides:

printBorder in class JComponent

Parameters:

g - the Graphics context in which to paint

See Also:

JComponent.print(java.awt.Graphics)

printComponents

public final void printComponents(java.awt.Graphics g)