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## 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

public class BasicScrollPaneUI
extends ScrollPaneUI
implements ScrollPaneConstants

A default L&F implementation of ScrollPaneUI.

Nested Class Summary
`class` | `BasicScrollPaneUI.HSBChangeListener` Horizontal scrollbar listener.
`protected class` | `BasicScrollPaneUI.MouseWheelHandler` MouseWheelHandler is an inner class which implements the MouseWheelListener interface.
`class` | `BasicScrollPaneUI.PropertyChangeHandler`
`class` | `BasicScrollPaneUI.ViewportChangeHandler` Listener for viewport events.
`class` | `BasicScrollPaneUI.VSBChangeListener` Vertical scrollbar listener.

Field Summary
`protected ChangeListener` | `hsbChangeListener`
`protected JScrollPane` | `scrollpane`
`protected PropertyChangeListener` | `spPropertyChangeListener`
`protected ChangeListener` | `viewportChangeListener`
`protected ChangeListener` | `vsbChangeListener`

Fields inherited from 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
`BasicScrollPaneUI()`

Method Summary
`protected ChangeListener` | `createHSBChangeListener()`
`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 an instance of the UI delegate for the specified component.
`protected ChangeListener` | `createViewportChangeListener()`
`protected ChangeListener` | `createVSBChangeListener()`
`Dimension` | `getMaximumSize(JComponent c)` Returns the specified component's maximum size appropriate for the look and feel.
`Dimension` | `getMinimumSize(JComponent c)` Returns the specified component's minimum size appropriate for the look and feel.
`Dimension` | `getPreferredSize(JComponent c)` Returns the specified component's preferred size appropriate for the look and feel.
`protected void` | `installDefaults(JScrollPane scrollpane)`
`protected void` | `installKeyboardActions(JScrollPane c)`
`protected void` | `installListeners(JScrollPane c)`
`void` | `installUI(JComponent x)` Configures the specified component appropriate for the look and feel.
`void` | `paint(Graphics g, JComponent c)` Paints the specified component appropriate for the look and feel.
`protected void` | `syncScrollPaneWithViewport()`
`protected void` | `uninstallDefaults(JScrollPane c)`
`protected void` | `uninstallKeyboardActions(JScrollPane c)`
`protected void` | `uninstallListeners(JComponent c)`
`void` | `uninstallUI(JComponent c)` Reverses configuration which was done on the specified component during `installUI`.
`protected void` | `updateColumnHeader(PropertyChangeEvent e)`
`protected void` | `updateRowHeader(PropertyChangeEvent e)`
`protected void` | `updateScrollBarDisplayPolicy(PropertyChangeEvent e)`
`protected void` | `updateViewport(PropertyChangeEvent e)`

Methods inherited from class javax.swing.plaf.ComponentUI
`contains, getAccessibleChild, getAccessibleChildrenCount, update`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### scrollpane

    protected JScrollPane scrollpane

### vsbChangeListener

    protected ChangeListener vsbChangeListener

### hsbChangeListener

    protected ChangeListener hsbChangeListener

### viewportChangeListener

    protected ChangeListener viewportChangeListener

### spPropertyChangeListener

    protected PropertyChangeListener spPropertyChangeListener

Constructor Detail

### BasicScrollPaneUI

    public BasicScrollPaneUI()

Method Detail

### createUI

    public static ComponentUI createUI(JComponent x)

  Description copied from class: `ComponentUI`
  Returns an instance of the UI delegate for the specified component. Each subclass must provide its own static `createUI` method that returns an instance of that UI delegate subclass. If the UI delegate subclass is stateless, it may return an instance that is shared by multiple components. If the UI delegate is stateful, then it should return a new instance per component. The default implementation of this method throws an error, as it should never be invoked.

### paint

    public void paint(Graphics g,
                      JComponent c)

  Description copied from class: `ComponentUI`
  Paints the specified component appropriate for the look and feel. This method is invoked from the `ComponentUI.update` method when the specified component is being painted. Subclasses should override this method and use the specified `Graphics` object to render the content of the component.

  Overrides:
    `paint` in class `ComponentUI`
  Parameters:
    `g` - the `Graphics` context in which to paint
    `c` - the component being painted; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components
  See Also:
    `ComponentUI.update(java.awt.Graphics, javax.swing.JComponent)`

### getPreferredSize

    public Dimension getPreferredSize(JComponent c)

  Description copied from class: `ComponentUI`
  Returns the specified component's preferred size appropriate for the look and feel. If `null` is returned, the preferred 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 returns `null`.

  Overrides:
    `getPreferredSize` in class `ComponentUI`
  Parameters:
    `c` - the component whose preferred 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:
    null which indicates that the LayoutManager will compute the value
  See Also:
    `JComponent.getPreferredSize()`

### getMinimumSize

    public Dimension getMinimumSize(JComponent c)

  Description copied from class: `ComponentUI`
  Returns the specified component's minimum size appropriate for the look and feel. If `null` is returned, the minimum 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:
    `getMinimumSize` in class `ComponentUI`
  Parameters:
    `c` - the component whose minimum 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:
    the preferred size
  See Also:
    `getPreferredSize(javax.swing.JComponent)`

### 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)

### installListeners

    protected void installListeners(JScrollPane c)

### installKeyboardActions

    protected void installKeyboardActions(JScrollPane c)

### installUI

    public void installUI(JComponent x)

  Description copied from class: `ComponentUI`
  Configures the specified component appropriate for the look and feel. This method is invoked when the `ComponentUI` instance is being installed as the UI delegate on the specified component. This method should completely configure the component for the look and feel, including the following:
  1. Install any default property values for color, fonts, borders, icons, opacity, etc. on the component. Whenever possible, property values initialized by the client program should not be overridden.
  2. Install a `LayoutManager` on the component if necessary.
  3. Create/add any required sub-components to the component.
  4. Create/install event listeners on the component.
  5. Create/install a `PropertyChangeListener` on the component in order to detect and respond to component property changes appropriately.
  6. Install keyboard UI (mnemonics, traversal, etc.) on the component.
  7. Initialize any appropriate instance data.

  Overrides:
    `installUI` in class `ComponentUI`
  Parameters:
    `x` - the component where this UI delegate is being installed
  See Also:
    `ComponentUI.uninstallUI(javax.swing.JComponent)`, `JComponent.setUI(javax.swing.plaf.ComponentUI)`, `JComponent.updateUI()`

### uninstallDefaults

    protected void uninstallDefaults(JScrollPane c)

### uninstallListeners

    protected void uninstallListeners(JComponent c)

### uninstallKeyboardActions

    protected void uninstallKeyboardActions(JScrollPane c)

### uninstallUI

    public void uninstallUI(JComponent c)

  Description copied from class: `ComponentUI`
  Reverses configuration which was done on the specified component during `installUI`. This method is invoked when this `UIComponent` instance is being removed as the UI delegate for the specified component. This method should undo the configuration performed in `installUI`, being careful to leave the `JComponent` instance in a clean state (no extraneous listeners, look-and-feel-specific property objects, etc.). This should include the following:
  1. Remove any UI-set borders from the component.
  2. Remove any UI-set layout managers on the component.
  3. Remove any UI-added sub-components from the component.
  4. Remove any UI-added event/property listeners from the component.
  5. Remove any UI-installed keyboard UI from the component.
  6. Nullify any allocated instance data objects to allow for GC.

  Overrides:
    `uninstallUI` in class `ComponentUI`
  Parameters:
    `c` - the component from which this UI delegate is being removed; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components
  See Also:
    `ComponentUI.installUI(javax.swing.JComponent)`, `JComponent.updateUI()`

### syncScrollPaneWithViewport

    protected void syncScrollPaneWithViewport()

### createViewportChangeListener

    protected ChangeListener createViewportChangeListener()

### createHSBChangeListener

    protected ChangeListener createHSBChangeListener()

### createVSBChangeListener

    protected ChangeListener createVSBChangeListener()

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

### updateScrollBarDisplayPolicy

    protected void updateScrollBarDisplayPolicy(PropertyChangeEvent e)

### updateViewport

    protected void updateViewport(PropertyChangeEvent e)

### updateRowHeader

    protected void updateRowHeader(PropertyChangeEvent e)

### updateColumnHeader

    protected void updateColumnHeader(PropertyChangeEvent e)

### 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);
              }
          }
       }

  See Also:
    `PropertyChangeListener`, `installUI(javax.swing.JComponent)`

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