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/OpenJDK 21

Class BasicScrollBarUI

java.lang.Object
javax.swing.plaf.ComponentUI
javax.swing.plaf.ScrollBarUI
javax.swing.plaf.basic.BasicScrollBarUI
All Implemented Interfaces:
LayoutManager, SwingConstants
Direct Known Subclasses:
MetalScrollBarUI, SynthScrollBarUI 
public class BasicScrollBarUI extends ScrollBarUI implements LayoutManager, SwingConstants
Implementation of ScrollBarUI for the Basic Look and Feel

Nested Class Summary

Modifier and Type Class Description
protected class  BasicScrollBarUI.ArrowButtonListener
Listener for cursor keys.
protected class  BasicScrollBarUI.ModelListener
A listener to listen for model changes.
class  BasicScrollBarUI.PropertyChangeHandler
Property change handler
protected class  BasicScrollBarUI.ScrollListener
Listener for scrolling events initiated in the ScrollPane.
protected class  BasicScrollBarUI.TrackListener
Track mouse drags.

Field Summary

Modifier and Type Field Description
protected BasicScrollBarUI.ArrowButtonListener buttonListener
Button listener
protected JButton decrButton
Decrement button
protected static final int DECREASE_HIGHLIGHT
Decrease highlight
protected int decrGap
Distance between the decrement button and the track.
protected JButton incrButton
Increment button
protected static final int INCREASE_HIGHLIGHT
Increase highlight
protected int incrGap
Distance between the increment button and the track.
protected boolean isDragging
Dragging
protected Dimension maximumThumbSize
Maximum thumb size
protected Dimension minimumThumbSize
Minimum thumb size
protected BasicScrollBarUI.ModelListener modelListener
Model listener
protected static final int NO_HIGHLIGHT
No highlight
protected PropertyChangeListener propertyChangeListener
Property change listener
protected JScrollBar scrollbar
Scrollbar
protected int scrollBarWidth
Hint as to what width (when vertical) or height (when horizontal) should be.
protected BasicScrollBarUI.ScrollListener scrollListener
Scroll listener
protected Timer scrollTimer
Scroll timer
protected Color thumbColor
Thumb color
protected Color thumbDarkShadowColor
Thumb dark shadow color
protected Color thumbHighlightColor
Thumb highlight color
protected Color thumbLightShadowColor
Thumb light shadow color
protected Rectangle thumbRect
Thumb rectangle
protected Color trackColor
Track color
protected int trackHighlight
Track highlight
protected Color trackHighlightColor
Track highlight color
protected BasicScrollBarUI.TrackListener trackListener
Track listener
protected Rectangle trackRect
Track rectangle

Fields declared in interface javax.swing.SwingConstants

BOTTOM, CENTER, EAST, HORIZONTAL, LEADING, LEFT, NEXT, NORTH, NORTH_EAST, NORTH_WEST, PREVIOUS, RIGHT, SOUTH, SOUTH_EAST, SOUTH_WEST, TOP, TRAILING, VERTICAL, WEST

Constructor Summary

Constructor Description
BasicScrollBarUI()
Constructs a BasicScrollBarUI.

Method Summary

Modifier and Type Method Description
void addLayoutComponent(String name, Component child)
If the layout manager uses a per-component string, adds the component comp to the layout, associating it with the string specified by name.
protected void configureScrollBarColors()
Configures the scroll bar colors.
protected BasicScrollBarUI.ArrowButtonListener createArrowButtonListener()
Creates an arrow button listener.
protected JButton createDecreaseButton(int orientation)
Creates a decrease button.
protected JButton createIncreaseButton(int orientation)
Creates an increase button.
protected BasicScrollBarUI.ModelListener createModelListener()
Creates a model listener.
protected PropertyChangeListener createPropertyChangeListener()
Creates a property change listener.
protected BasicScrollBarUI.ScrollListener createScrollListener()
Creates a scroll listener.
protected BasicScrollBarUI.TrackListener createTrackListener()
Creates a track listener.
static ComponentUI createUI(JComponent c)
Creates the UI.
Dimension getMaximumSize(JComponent c)
Returns the specified component's maximum size appropriate for the look and feel.
protected Dimension getMaximumThumbSize()
Returns the largest acceptable size for the thumb.
protected Dimension getMinimumThumbSize()
Returns the smallest acceptable size for the thumb.
Dimension getPreferredSize(JComponent c)
A vertical scrollbar's preferred width is the maximum of preferred widths of the (non null) increment/decrement buttons, and the minimum width of the thumb.
boolean getSupportsAbsolutePositioning()
Indicates whether the user can absolutely position the thumb with a mouse gesture (usually the middle mouse button).
protected Rectangle getThumbBounds()
Return the current size/location of the thumb.
protected Rectangle getTrackBounds()
Returns the current bounds of the track, i.e. the space in between the increment and decrement buttons, less the insets.
protected void installComponents()
Installs the components.
protected void installDefaults()
Installs the defaults.
protected void installKeyboardActions()
Installs the keyboard actions.
protected void installListeners()
Installs the listeners.
void installUI(JComponent c)
Installs the UI.
boolean isThumbRollover()
Returns true if the mouse is currently over the thumb.
void layoutContainer(Container scrollbarContainer)
Lays out the specified container.
protected void layoutHScrollbar(JScrollBar sb)
Lays out a horizontal scroll bar.
protected void layoutVScrollbar(JScrollBar sb)
Lays out a vertical scroll bar.
Dimension minimumLayoutSize(Container scrollbarContainer)
Calculates the minimum size dimensions for the specified container, given the components it contains.
protected void paintDecreaseHighlight(Graphics g)
Paints the decrease highlight.
protected void paintIncreaseHighlight(Graphics g)
Paints the increase highlight.
protected void paintThumb(Graphics g, JComponent c, Rectangle thumbBounds)
Paints the thumb.
protected void paintTrack(Graphics g, JComponent c, Rectangle trackBounds)
Paints the track.
Dimension preferredLayoutSize(Container scrollbarContainer)
Calculates the preferred size dimensions for the specified container, given the components it contains.
void removeLayoutComponent(Component child)
Removes the specified component from the layout.
protected void scrollByBlock(int direction)
Scrolls by block.
protected void scrollByUnit(int direction)
Scrolls by unit.
protected void setThumbBounds(int x, int y, int width, int height)
Set the bounds of the thumb and force a repaint that includes the old thumbBounds and the new one.
protected void setThumbRollover(boolean active)
Sets whether or not the mouse is currently over the thumb.
protected void uninstallComponents()
Uninstalls the components.
protected void uninstallDefaults()
Uninstalls the defaults.
protected void uninstallKeyboardActions()
Uninstalls the keyboard actions.
protected void uninstallListeners()
Uninstall the listeners.
void uninstallUI(JComponent c)
Uninstalls the UI.

Methods declared in class javax.swing.plaf.ComponentUI

contains, getAccessibleChild, getAccessibleChildrenCount, getBaseline, getBaselineResizeBehavior, getMinimumSize, paint, update

Methods declared in class java.lang.Object

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

Field Details

minimumThumbSize

protected Dimension minimumThumbSize
Minimum thumb size

maximumThumbSize

protected Dimension maximumThumbSize
Maximum thumb size

thumbHighlightColor

protected Color thumbHighlightColor
Thumb highlight color

thumbLightShadowColor

protected Color thumbLightShadowColor
Thumb light shadow color

thumbDarkShadowColor

protected Color thumbDarkShadowColor
Thumb dark shadow color

thumbColor

protected Color thumbColor
Thumb color

trackColor

protected Color trackColor
Track color

trackHighlightColor

protected Color trackHighlightColor
Track highlight color

scrollbar

protected JScrollBar scrollbar
Scrollbar

incrButton

protected JButton incrButton
Increment button

decrButton

protected JButton decrButton
Decrement button

isDragging

protected boolean isDragging
Dragging

trackListener

protected BasicScrollBarUI.TrackListener trackListener
Track listener

buttonListener

protected BasicScrollBarUI.ArrowButtonListener buttonListener
Button listener

modelListener

protected BasicScrollBarUI.ModelListener modelListener
Model listener

thumbRect

protected Rectangle thumbRect
Thumb rectangle

trackRect

protected Rectangle trackRect
Track rectangle

trackHighlight

protected int trackHighlight
Track highlight

NO_HIGHLIGHT

protected static final int NO_HIGHLIGHT
No highlight
See Also:

DECREASE_HIGHLIGHT

protected static final int DECREASE_HIGHLIGHT
Decrease highlight
See Also:

INCREASE_HIGHLIGHT

protected static final int INCREASE_HIGHLIGHT
Increase highlight
See Also:

scrollListener

protected BasicScrollBarUI.ScrollListener scrollListener
Scroll listener

propertyChangeListener

protected PropertyChangeListener propertyChangeListener
Property change listener

scrollTimer

protected Timer scrollTimer
Scroll timer

scrollBarWidth

protected int scrollBarWidth
Hint as to what width (when vertical) or height (when horizontal) should be.
Since:
1.7

incrGap

protected int incrGap
Distance between the increment button and the track. This may be a negative number. If negative, then an overlap between the button and track will occur, which is useful for shaped buttons.
Since:
1.7

decrGap

protected int decrGap
Distance between the decrement button and the track. This may be a negative number. If negative, then an overlap between the button and track will occur, which is useful for shaped buttons.
Since:
1.7

Constructor Details

BasicScrollBarUI

public BasicScrollBarUI()
Constructs a BasicScrollBarUI.

Method Details

createUI

public static ComponentUI createUI(JComponent c)
Creates the UI.
Parameters:
c - the component
Returns:
the UI

configureScrollBarColors

protected void configureScrollBarColors()
Configures the scroll bar colors.

installUI

public void installUI(JComponent c)
Installs the UI.
Overrides:
installUI in class ComponentUI
Parameters:
c - the component
See Also:

uninstallUI

public void uninstallUI(JComponent c)
Uninstalls the UI.
Overrides:
uninstallUI in class ComponentUI
Parameters:
c - the component
See Also:

installDefaults

protected void installDefaults()
Installs the defaults.

installComponents

protected void installComponents()
Installs the components.

uninstallComponents

protected void uninstallComponents()
Uninstalls the components.

installListeners

protected void installListeners()
Installs the listeners.

installKeyboardActions

protected void installKeyboardActions()
Installs the keyboard actions.

uninstallKeyboardActions

protected void uninstallKeyboardActions()
Uninstalls the keyboard actions.

uninstallListeners

protected void uninstallListeners()
Uninstall the listeners.

uninstallDefaults

protected void uninstallDefaults()
Uninstalls the defaults.

createTrackListener

protected BasicScrollBarUI.TrackListener createTrackListener()
Creates a track listener.
Returns:
a track listener

createArrowButtonListener

protected BasicScrollBarUI.ArrowButtonListener createArrowButtonListener()
Creates an arrow button listener.
Returns:
an arrow button listener

createModelListener

protected BasicScrollBarUI.ModelListener createModelListener()
Creates a model listener.
Returns:
a model listener

createScrollListener

protected BasicScrollBarUI.ScrollListener createScrollListener()
Creates a scroll listener.
Returns:
a scroll listener

createPropertyChangeListener

protected PropertyChangeListener createPropertyChangeListener()
Creates a property change listener.
Returns:
a property change listener

setThumbRollover

protected void setThumbRollover(boolean active)
Sets whether or not the mouse is currently over the thumb.
Parameters:
active - True indicates the thumb is currently active.
Since:
1.5

isThumbRollover

public boolean isThumbRollover()
Returns true if the mouse is currently over the thumb.
Returns:
true if the thumb is currently active
Since:
1.5

getPreferredSize

public Dimension getPreferredSize(JComponent c)
A vertical scrollbar's preferred width is the maximum of preferred widths of the (non null) increment/decrement buttons, and the minimum width of the thumb. The preferred height is the sum of the preferred heights of the same parts. The basis for the preferred size of a horizontal scrollbar is similar.

The preferredSize is only computed once, subsequent calls to this method just return a cached size.

Overrides:
getPreferredSize in class ComponentUI
Parameters:
c - the JScrollBar that's delegating this method to us
Returns:
the preferred size of a Basic JScrollBar
See Also:

getMaximumSize

public Dimension getMaximumSize(JComponent c)
Description copied from class: ComponentUI
Returns the specified component's maximum size appropriate for the look and feel. If null is returned, the maximum size will be calculated by the component's layout manager instead (this is the preferred approach for any component with a specific layout manager installed). The default implementation of this method invokes getPreferredSize and returns that value.
Overrides:
getMaximumSize in class ComponentUI
Parameters:
c - The JScrollBar that's delegating this method to us.
Returns:
new Dimension(Integer.MAX_VALUE, Integer.MAX_VALUE);
See Also:

createDecreaseButton

protected JButton createDecreaseButton(int orientation)
Creates a decrease button.
Parameters:
orientation - the orientation
Returns:
a decrease button

createIncreaseButton

protected JButton createIncreaseButton(int orientation)
Creates an increase button.
Parameters:
orientation - the orientation
Returns:
an increase button

paintDecreaseHighlight

protected void paintDecreaseHighlight(Graphics g)
Paints the decrease highlight.
Parameters:
g - the graphics

paintIncreaseHighlight

protected void paintIncreaseHighlight(Graphics g)
Paints the increase highlight.
Parameters:
g - the graphics

paintTrack

protected void paintTrack(Graphics g, JComponent c, Rectangle trackBounds)
Paints the track.
Parameters:
g - the graphics
c - the component
trackBounds - the track bounds

paintThumb

protected void paintThumb(Graphics g, JComponent c, Rectangle thumbBounds)
Paints the thumb.
Parameters:
g - the graphics
c - the component
thumbBounds - the thumb bounds

getMinimumThumbSize

protected Dimension getMinimumThumbSize()
Returns the smallest acceptable size for the thumb. If the scrollbar becomes so small that this size isn't available, the thumb will be hidden.

Warning : the value returned by this method should not be be modified, it's a shared static constant.

Returns:
The smallest acceptable size for the thumb.
See Also:

getMaximumThumbSize

protected Dimension getMaximumThumbSize()
Returns the largest acceptable size for the thumb. To create a fixed size thumb one make this method and getMinimumThumbSize return the same value.

Warning : the value returned by this method should not be be modified, it's a shared static constant.

Returns:
The largest acceptable size for the thumb.
See Also:

addLayoutComponent

public void addLayoutComponent(String name, Component child)
Description copied from interface: LayoutManager
If the layout manager uses a per-component string, adds the component comp to the layout, associating it with the string specified by name.
Specified by:
addLayoutComponent in interface LayoutManager
Parameters:
name - the string to be associated with the component
child - the component to be added

removeLayoutComponent

public void removeLayoutComponent(Component child)
Description copied from interface: LayoutManager
Removes the specified component from the layout.
Specified by:
removeLayoutComponent in interface LayoutManager
Parameters:
child - the component to be removed

preferredLayoutSize

public Dimension preferredLayoutSize(Container scrollbarContainer)
Description copied from interface: LayoutManager
Calculates the preferred size dimensions for the specified container, given the components it contains.
Specified by:
preferredLayoutSize in interface LayoutManager
Parameters:
scrollbarContainer - the container to be laid out
Returns:
the preferred dimension for the container
See Also:

minimumLayoutSize

public Dimension minimumLayoutSize(Container scrollbarContainer)
Description copied from interface: LayoutManager
Calculates the minimum size dimensions for the specified container, given the components it contains.
Specified by:
minimumLayoutSize in interface LayoutManager
Parameters:
scrollbarContainer - the component to be laid out
Returns:
the minimum dimension for the container
See Also:

layoutVScrollbar

protected void layoutVScrollbar(JScrollBar sb)
Lays out a vertical scroll bar.
Parameters:
sb - the scroll bar

layoutHScrollbar

protected void layoutHScrollbar(JScrollBar sb)
Lays out a horizontal scroll bar.
Parameters:
sb - the scroll bar

layoutContainer

public void layoutContainer(Container scrollbarContainer)
Description copied from interface: LayoutManager
Lays out the specified container.
Specified by:
layoutContainer in interface LayoutManager
Parameters:
scrollbarContainer - the container to be laid out

setThumbBounds

protected void setThumbBounds(int x, int y, int width, int height)
Set the bounds of the thumb and force a repaint that includes the old thumbBounds and the new one.
Parameters:
x - set the x location of the thumb
y - set the y location of the thumb
width - set the width of the thumb
height - set the height of the thumb
See Also:

getThumbBounds

protected Rectangle getThumbBounds()
Return the current size/location of the thumb.

Warning : the value returned by this method should not be be modified, it's a reference to the actual rectangle, not a copy.

Returns:
The current size/location of the thumb.
See Also:

getTrackBounds

protected Rectangle getTrackBounds()
Returns the current bounds of the track, i.e. the space in between the increment and decrement buttons, less the insets. The value returned by this method is updated each time the scrollbar is laid out (validated).

Warning : the value returned by this method should not be be modified, it's a reference to the actual rectangle, not a copy.

Returns:
the current bounds of the scrollbar track
See Also:

scrollByBlock

protected void scrollByBlock(int direction)
Scrolls by block.
Parameters:
direction - the direction to scroll

scrollByUnit

protected void scrollByUnit(int direction)
Scrolls by unit.
Parameters:
direction - the direction to scroll

getSupportsAbsolutePositioning

public boolean getSupportsAbsolutePositioning()
Indicates whether the user can absolutely position the thumb with a mouse gesture (usually the middle mouse button).
Returns:
true if a mouse gesture can absolutely position the thumb
Since:
1.5

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https://docs.oracle.com/en/java/javase/21/docs/api/java.desktop/javax/swing/plaf/basic/BasicScrollBarUI.html