javax.swing
Class JScrollBar

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
              |
              +--javax.swing.JComponent
                    |
                    +--javax.swing.JScrollBar

Direct Known Subclasses:

JScrollPane.ScrollBar

public class JScrollBar

extends JComponent

implements Adjustable, Accessible

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 postion 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. A future release of Swing will provide support for long term persistence.

See Also:

JScrollPane, Serialized Form

Inner Class Summary

protected class

JScrollBar.AccessibleJScrollBar The class used to obtain the accessible role for this object.

Inner classes inherited from class javax.swing.JComponent

JComponent.AccessibleJComponent

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

accessibleContext, listenerList, TOOL_TIP_TEXT_KEY, ui, 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

Constructor Summary

JScrollBar()
Creates a vertical scrollbar with the following initial values: minimum = 0 maximum = 100 value = 0 extent = 10

JScrollBar(int orientation)
Creates a scrollbar with the specified orientation and the following initial values: minimum = 0 maximum = 100 value = 0 extent = 10

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

Method Summary

void	addAdjustmentListener(AdjustmentListener l) Adds an AdjustmentListener.
protected void	fireAdjustmentValueChanged(int id, int type, int value)
AccessibleContext	getAccessibleContext() Get the AccessibleContext associated with this JComponent
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).
ScrollBarUI	getUI() Returns the delegate that implements the look and feel for this component.
String	getUIClassID() Returns the name of the LookAndFeel class for this component.
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".
protected String	paramString() Returns a string representation of this JScrollBar.
void	removeAdjustmentListener(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: minimum <= value <= value+extent <= maximum
void	setVisibleAmount(int extent) Set the model's extent property.
void	updateUI() Overrides JComponent.updateUI.

Methods inherited from class javax.swing.JComponent

addAncestorListener, addNotify, addPropertyChangeListener, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getAlignmentX, getAlignmentY, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getConditionForKeyStroke, getDebugGraphicsOptions, getGraphics, getHeight, getInsets, getInsets, getLocation, getNextFocusableComponent, getPreferredSize, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getVisibleRect, getWidth, getX, getY, grabFocus, hasFocus, isDoubleBuffered, isFocusCycleRoot, isFocusTraversable, isLightweightComponent, isManagingFocus, isOpaque, isOptimizedDrawingEnabled, isPaintingTile, isRequestFocusEnabled, isValidateRoot, paint, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, processComponentKeyEvent, processFocusEvent, processKeyEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removePropertyChangeListener, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setBorder, setDebugGraphicsOptions, setDoubleBuffered, setFont, setForeground, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setUI, setVisible, unregisterKeyboardAction, update

Methods inherited from class java.awt.Container

add, add, add, add, add, addContainerListener, addImpl, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getLayout, insets, invalidate, isAncestorOf, layout, list, list, locate, minimumSize, paintComponents, preferredSize, print, printComponents, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, setLayout, validate, validateTree

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addPropertyChangeListener, bounds, checkImage, checkImage, coalesceEvents, contains, createImage, createImage, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, getBackground, getBounds, getColorModel, getComponentOrientation, getCursor, getDropTarget, getFont, getFontMetrics, getForeground, getInputContext, getInputMethodRequests, getLocale, getLocation, getLocationOnScreen, getName, getParent, getPeer, getSize, getToolkit, getTreeLock, gotFocus, handleEvent, hide, imageUpdate, inside, isDisplayable, isEnabled, isLightweight, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, printAll, processComponentEvent, processInputMethodEvent, processMouseEvent, remove, removeComponentListener, removeFocusListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removePropertyChangeListener, repaint, repaint, repaint, resize, resize, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setLocale, setLocation, setLocation, setName, setSize, setSize, show, show, size, toString, transferFocus

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, mimimum, 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:

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

getUI

public ScrollBarUI getUI()

Returns the delegate that implements the look and feel for this component.

See Also:

JComponent.setUI(javax.swing.plaf.ComponentUI)

updateUI

public void updateUI()

Overrides JComponent.updateUI.

Overrides:

updateUI in class JComponent

See Also:

JComponent.updateUI()

getUIClassID

public String getUIClassID()

Returns the name of the LookAndFeel class for this component.

Returns:

"ScrollBarUI"

Overrides:

getUIClassID in class JComponent

See Also:

JComponent.getUIClassID(), UIDefaults.getUI(javax.swing.JComponent)

getOrientation

public int getOrientation()

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

Specified by:

getOrientation in interface 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:

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 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 Adjustable

See Also:

getBlockIncrement()

getUnitIncrement

public int getUnitIncrement()

For backwards compatibility with java.awt.Scrollbar.

Specified by:

getUnitIncrement in interface Adjustable

See Also:

Adjustable.getUnitIncrement(), getUnitIncrement(int)

getBlockIncrement

public int getBlockIncrement()

For backwards compatibility with java.awt.Scrollbar.

Specified by:

getBlockIncrement in interface Adjustable

See Also:

Adjustable.getBlockIncrement(), getBlockIncrement(int)

getValue

public int getValue()

Returns the scrollbar's value.

Specified by:

getValue in interface 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 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 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 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 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 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 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 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(AdjustmentListener l)

Adds an AdjustmentListener. Adjustment listeners are notified each time the scrollbar's model changes. Adjustment events are provided for backwards compatability 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 Adjustable

Parameters:

l - the AdjustmentLister to add

See Also:

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

removeAdjustmentListener

public void removeAdjustmentListener(AdjustmentListener l)

Removes an AdjustmentEvent listener.

Specified by:

removeAdjustmentListener in interface Adjustable

Parameters:

l - the AdjustmentLister to remove

See Also:

addAdjustmentListener(java.awt.event.AdjustmentListener)

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

getMaximumSize

public Dimension getMaximumSize()

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

Overrides:

getMaximumSize in class JComponent

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.

Parameters:

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

Overrides:

setEnabled in class JComponent

paramString

protected 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.

Overriding paramString() to provide information about the specific new aspects of the JFC components.

Returns:

a string representation of this JScrollBar.

Overrides:

paramString in class JComponent

getAccessibleContext

public AccessibleContext getAccessibleContext()

Get the AccessibleContext associated with this JComponent

Specified by:

getAccessibleContext in interface Accessible

Returns:

the AccessibleContext of this JComponent

Overrides:

getAccessibleContext in class JComponent