Module java.desktop
Package javax.swing.plaf.basic

# 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

Nested Classes
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

Fields
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

Constructors
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:
  - `JComponent.getMaximumSize()`
  - `LayoutManager2.maximumLayoutSize(java.awt.Container)`

### 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:
  - `JComponent.getBaseline(int, int)`

### 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:
  - `JComponent.getBaseline(int, int)`

### 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:
  - `ComponentUI.installUI(javax.swing.JComponent)`
  - `BasicScrollPaneUI.MouseWheelHandler`

### 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:
  - `PropertyChangeListener`
  - `ComponentUI.installUI(javax.swing.JComponent)`