ch.randelshofer.gui
Class ScrollablePanels

java.lang.Object
  ch.randelshofer.gui.ScrollablePanels

public class ScrollablePanels
extends java.lang.Object

Helper class for panels that implement the Scrollable interface.

Author:

Werner Randelshofer

Method Summary

static java.awt.Dimension	getPreferredScrollableViewportSize(javax.swing.JPanel component) Returns the preferred size of the viewport for a view component.
static int	getScrollableBlockIncrement(javax.swing.JPanel component, java.awt.Rectangle visibleRect, int orientation, int direction) Components that display logical rows or columns should compute the scroll increment that will completely expose one block of rows or columns, depending on the value of orientation.
static boolean	getScrollableTracksViewportHeight(javax.swing.JPanel component) Return true if a viewport should always force the height of this Scrollable to match the height of the viewport.
static boolean	getScrollableTracksViewportWidth(javax.swing.JPanel component) Return true if a viewport should always force the width of this Scrollable to match the width of the viewport.
static int	getScrollableUnitIncrement(javax.swing.JPanel component, java.awt.Rectangle visibleRect, int orientation, int direction) Components that display logical rows or columns should compute the scroll increment that will completely expose one new row or column, depending on the value of orientation.

Methods inherited from class java.lang.Object

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

Method Detail

getPreferredScrollableViewportSize

public static java.awt.Dimension getPreferredScrollableViewportSize(javax.swing.JPanel component)

Returns the preferred size of the viewport for a view component. For example the preferredSize of a JList component is the size required to accommodate all of the cells in its list however the value of preferredScrollableViewportSize is the size required for JList.getVisibleRowCount() rows. A component without any properties that would effect the viewport size should just return getPreferredSize() here.

Returns:

The preferredSize of a JViewport whose view is this Scrollable.

See Also:

JComponent.getPreferredSize()

getScrollableBlockIncrement

public static int getScrollableBlockIncrement(javax.swing.JPanel component,
                                              java.awt.Rectangle visibleRect,
                                              int orientation,
                                              int direction)

Components that display logical rows or columns should compute the scroll increment that will completely expose one block of rows or columns, depending on the value of orientation.

Scrolling containers, like JScrollPane, will use this method each time the user requests a block scroll.

Parameters:

visibleRect - The view area visible within the viewport

orientation - Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL.

direction - Less than zero to scroll up/left, greater than zero for down/right.

Returns:

The "block" increment for scrolling in the specified direction. This value should always be positive.

See Also:

JScrollBar.setBlockIncrement(int)

getScrollableTracksViewportHeight

public static boolean getScrollableTracksViewportHeight(javax.swing.JPanel component)

Return true if a viewport should always force the height of this Scrollable to match the height of the viewport. For example a columnar text view that flowed text in left to right columns could effectively disable vertical scrolling by returning true here.

Scrolling containers, like JViewport, will use this method each time they are validated.

Returns:

True if a viewport should force the Scrollables height to match its own.

getScrollableTracksViewportWidth

public static boolean getScrollableTracksViewportWidth(javax.swing.JPanel component)

Return true if a viewport should always force the width of this Scrollable to match the width of the viewport. For example a normal text view that supported line wrapping would return true here, since it would be undesirable for wrapped lines to disappear beyond the right edge of the viewport. Note that returning true for a Scrollable whose ancestor is a JScrollPane effectively disables horizontal scrolling.

Scrolling containers, like JViewport, will use this method each time they are validated.

Returns:

True if a viewport should force the Scrollables width to match its own.

getScrollableUnitIncrement

public static int getScrollableUnitIncrement(javax.swing.JPanel component,
                                             java.awt.Rectangle visibleRect,
                                             int orientation,
                                             int direction)

Components that display logical rows or columns should compute the scroll increment that will completely expose one new row or column, depending on the value of orientation. Ideally, components should handle a partially exposed row or column by returning the distance required to completely expose the item.

Scrolling containers, like JScrollPane, will use this method each time the user requests a unit scroll.

Parameters:

visibleRect - The view area visible within the viewport

orientation - Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL.

direction - Less than zero to scroll up/left, greater than zero for down/right.

Returns:

The "unit" increment for scrolling in the specified direction. This value should always be positive.

See Also:

JScrollBar.setUnitIncrement(int)