W3cubDocs

Class BasicScrollPaneUI

java.lang.Object

javax.swing.plaf.ComponentUI

javax.swing.plaf.ScrollPaneUI

javax.swing.plaf.basic.BasicScrollPaneUI

All Implemented Interfaces:: ScrollPaneConstants

Direct Known Subclasses:: MetalScrollPaneUI, SynthScrollPaneUI

public class BasicScrollPaneUI extends ScrollPaneUI implements ScrollPaneConstants

A default L&F implementation of ScrollPaneUI.

Nested Class Summary

Modifier and Type	Class	Description
`class`	`BasicScrollPaneUI.HSBChangeListener`	Deprecated, for removal: This API element is subject to removal in a future version.
`protected class`	`BasicScrollPaneUI.MouseWheelHandler`	MouseWheelHandler is an inner class which implements the MouseWheelListener interface.
`class`	`BasicScrollPaneUI.PropertyChangeHandler`	Deprecated, for removal: This API element is subject to removal in a future version.
`class`	`BasicScrollPaneUI.ViewportChangeHandler`	Deprecated, for removal: This API element is subject to removal in a future version.
`class`	`BasicScrollPaneUI.VSBChangeListener`	Deprecated, for removal: This API element is subject to removal in a future version.

Field Summary

Modifier and Type	Field	Description
`protected ChangeListener`	`hsbChangeListener`	`ChangeListener` installed on the horizontal scrollbar.
`protected JScrollPane`	`scrollpane`	The instance of `JScrollPane`.
`protected PropertyChangeListener`	`spPropertyChangeListener`	`PropertyChangeListener` installed on the scroll pane.
`protected ChangeListener`	`viewportChangeListener`	`ChangeListener` installed on the viewport.
`protected ChangeListener`	`vsbChangeListener`	`ChangeListener` installed on the vertical scrollbar.

Fields declared in interface javax.swing.ScrollPaneConstants

COLUMN_HEADER, HORIZONTAL_SCROLLBAR, HORIZONTAL_SCROLLBAR_ALWAYS, HORIZONTAL_SCROLLBAR_AS_NEEDED, HORIZONTAL_SCROLLBAR_NEVER, HORIZONTAL_SCROLLBAR_POLICY, LOWER_LEADING_CORNER, LOWER_LEFT_CORNER, LOWER_RIGHT_CORNER, LOWER_TRAILING_CORNER, ROW_HEADER, UPPER_LEADING_CORNER, UPPER_LEFT_CORNER, UPPER_RIGHT_CORNER, UPPER_TRAILING_CORNER, VERTICAL_SCROLLBAR, VERTICAL_SCROLLBAR_ALWAYS, VERTICAL_SCROLLBAR_AS_NEEDED, VERTICAL_SCROLLBAR_NEVER, VERTICAL_SCROLLBAR_POLICY, VIEWPORT

Constructor Summary

Constructor	Description
`BasicScrollPaneUI()`	Constructs a `BasicScrollPaneUI`.

Method Summary

Modifier and Type	Method	Description
`protected ChangeListener`	`createHSBChangeListener()`	Returns an instance of horizontal scroll bar `ChangeListener`.
`protected MouseWheelListener`	`createMouseWheelListener()`	Creates an instance of MouseWheelListener, which is added to the JScrollPane by installUI().
`protected PropertyChangeListener`	`createPropertyChangeListener()`	Creates an instance of `PropertyChangeListener` that's added to the `JScrollPane` by `installUI()`.
`static ComponentUI`	`createUI(JComponent x)`	Returns a new instance of `BasicScrollPaneUI`.
`protected ChangeListener`	`createViewportChangeListener()`	Returns an instance of viewport `ChangeListener`.
`protected ChangeListener`	`createVSBChangeListener()`	Returns an instance of vertical scroll bar `ChangeListener`.
`int`	`getBaseline(JComponent c, int width, int height)`	Returns the baseline.
`Component.BaselineResizeBehavior`	`getBaselineResizeBehavior(JComponent c)`	Returns an enum indicating how the baseline of the component changes as the size changes.
`Dimension`	`getMaximumSize(JComponent c)`	Returns the specified component's maximum size appropriate for the look and feel.
`protected void`	`installDefaults(JScrollPane scrollpane)`	Installs default properties.
`protected void`	`installKeyboardActions(JScrollPane c)`	Registers keyboard actions.
`protected void`	`installListeners(JScrollPane c)`	Registers listeners.
`protected void`	`syncScrollPaneWithViewport()`	Synchronizes the `JScrollPane` with `Viewport`.
`protected void`	`uninstallDefaults(JScrollPane c)`	Uninstalls default properties.
`protected void`	`uninstallKeyboardActions(JScrollPane c)`	Unregisters keyboard actions.
`protected void`	`uninstallListeners(JComponent c)`	Unregisters listeners.
`protected void`	`updateColumnHeader(PropertyChangeEvent e)`	Updates column header.
`protected void`	`updateRowHeader(PropertyChangeEvent e)`	Updates row header.
`protected void`	`updateScrollBarDisplayPolicy(PropertyChangeEvent e)`	Updates a scroll bar display policy.
`protected void`	`updateViewport(PropertyChangeEvent e)`	Updates viewport.

Methods declared in class javax.swing.plaf.ComponentUI

contains, getAccessibleChild, getAccessibleChildrenCount, getMinimumSize, getPreferredSize, installUI, paint, uninstallUI, update

Methods declared in class java.lang.Object

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

Field Details

scrollpane

protected JScrollPane scrollpane

The instance of JScrollPane.

vsbChangeListener

protected ChangeListener vsbChangeListener

ChangeListener installed on the vertical scrollbar.

hsbChangeListener

protected ChangeListener hsbChangeListener

ChangeListener installed on the horizontal scrollbar.

viewportChangeListener

protected ChangeListener viewportChangeListener

ChangeListener installed on the viewport.

spPropertyChangeListener

protected PropertyChangeListener spPropertyChangeListener

PropertyChangeListener installed on the scroll pane.

Constructor Details

BasicScrollPaneUI

public BasicScrollPaneUI()

Constructs a BasicScrollPaneUI.

Method Details

createUI

public static ComponentUI createUI(JComponent x)

Returns a new instance of BasicScrollPaneUI.

Parameters:: x - a component.
Returns:: a new instance of BasicScrollPaneUI

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 component whose maximum size is being queried; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components

Returns:

new Dimension(Short.MAX_VALUE, Short.MAX_VALUE)

See Also:

installDefaults

protected void installDefaults(JScrollPane scrollpane)

Installs default properties.

Parameters:: scrollpane - an instance of JScrollPane

installListeners

protected void installListeners(JScrollPane c)

Registers listeners.

Parameters:: c - an instance of JScrollPane

installKeyboardActions

protected void installKeyboardActions(JScrollPane c)

Registers keyboard actions.

Parameters:: c - an instance of JScrollPane

uninstallDefaults

protected void uninstallDefaults(JScrollPane c)

Uninstalls default properties.

Parameters:: c - an instance of JScrollPane

uninstallListeners

protected void uninstallListeners(JComponent c)

Unregisters listeners.

Parameters:: c - a component

uninstallKeyboardActions

protected void uninstallKeyboardActions(JScrollPane c)

Unregisters keyboard actions.

Parameters:: c - an instance of JScrollPane

syncScrollPaneWithViewport

protected void syncScrollPaneWithViewport()

Synchronizes the JScrollPane with Viewport.

getBaseline

public int getBaseline(JComponent c, int width, int height)

Returns the baseline.

Overrides:

getBaseline in class ComponentUI

Parameters:

c - JComponent baseline is being requested for

width - the width to get the baseline for

height - the height to get the baseline for

Returns:

baseline or a value < 0 indicating there is no reasonable baseline

Throws:

NullPointerException - if c is null

IllegalArgumentException - if width or height is < 0

Since:

1.6

See Also:

getBaselineResizeBehavior

public Component.BaselineResizeBehavior getBaselineResizeBehavior(JComponent c)

Returns an enum indicating how the baseline of the component changes as the size changes.

Overrides:

getBaselineResizeBehavior in class ComponentUI

Parameters:

c - JComponent to return baseline resize behavior for

Returns:

an enum indicating how the baseline changes as the component size changes

Throws:

NullPointerException - if c is null

Since:

1.6

See Also:

createViewportChangeListener

protected ChangeListener createViewportChangeListener()

Returns an instance of viewport ChangeListener.

Returns:: an instance of viewport ChangeListener

createHSBChangeListener

protected ChangeListener createHSBChangeListener()

Returns an instance of horizontal scroll bar ChangeListener.

Returns:: an instance of horizontal scroll bar ChangeListener

createVSBChangeListener

protected ChangeListener createVSBChangeListener()

Returns an instance of vertical scroll bar ChangeListener.

Returns:: an instance of vertical scroll bar ChangeListener

createMouseWheelListener

protected MouseWheelListener createMouseWheelListener()

Creates an instance of MouseWheelListener, which is added to the JScrollPane by installUI(). The returned MouseWheelListener is used to handle mouse wheel-driven scrolling.

Returns:

MouseWheelListener which implements wheel-driven scrolling

Since:

1.4

See Also:

updateScrollBarDisplayPolicy

protected void updateScrollBarDisplayPolicy(PropertyChangeEvent e)

Updates a scroll bar display policy.

Parameters:: e - the property change event

updateViewport

protected void updateViewport(PropertyChangeEvent e)

Updates viewport.

Parameters:: e - the property change event

updateRowHeader

protected void updateRowHeader(PropertyChangeEvent e)

Updates row header.

Parameters:: e - the property change event

updateColumnHeader

protected void updateColumnHeader(PropertyChangeEvent e)

Updates column header.

Parameters:: e - the property change event

createPropertyChangeListener

protected PropertyChangeListener createPropertyChangeListener()

Creates an instance of PropertyChangeListener that's added to the JScrollPane by installUI(). Subclasses can override this method to return a custom PropertyChangeListener, e.g.

 class MyScrollPaneUI extends BasicScrollPaneUI {
    protected PropertyChangeListener createPropertyChangeListener() {
        return new MyPropertyChangeListener();
    }
    public class MyPropertyChangeListener extends PropertyChangeListener {
        public void propertyChange(PropertyChangeEvent e) {
            if (e.getPropertyName().equals("viewport")) {
                // do some extra work when the viewport changes
            }
            super.propertyChange(e);
        }
    }
 }

Returns:

an instance of PropertyChangeListener

See Also:

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