javax.swing
class ScrollPaneLayout

java.lang.Object javax.swing.ScrollPaneLayout

All Implemented Interfaces:

LayoutManager, Serializable, ScrollPaneConstants

Direct Known Subclasses:

ScrollPaneLayout.UIResource

public class ScrollPaneLayout
extends Object
implements LayoutManager, ScrollPaneConstants, Serializable

The layout manager used by JScrollPane. JScrollPaneLayout is responsible for nine components: a viewport, two scrollbars, a row header, a column header, and four "corner" components.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans^TM has been added to the java.beans package. Please see {@link java.beans.XMLEncoder}.

colHead

protected JViewport colHead

The column header child. Default is null.

hsb

protected JScrollBar hsb

The scrollpane's horizontal scrollbar child. Default is a JScrollBar.

hsbPolicy

protected int hsbPolicy

The display policy for the horizontal scrollbar. The default is ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED.

This field is obsolete, please use the JScrollPane field instead.

lowerLeft

protected Component lowerLeft

The component to display in the lower left corner. Default is null.

lowerRight

protected Component lowerRight

The component to display in the lower right corner. Default is null.

rowHead

protected JViewport rowHead

The row header child. Default is null.

upperLeft

protected Component upperLeft

The component to display in the upper left corner. Default is null.

upperRight

protected Component upperRight

The component to display in the upper right corner. Default is null.

viewport

protected JViewport viewport

The scrollpane's viewport child. Default is an empty JViewport.

vsb

protected JScrollBar vsb

The scrollpane's vertical scrollbar child. Default is a JScrollBar.

vsbPolicy

protected int vsbPolicy

The display policy for the vertical scrollbar. The default is ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED.

This field is obsolete, please use the JScrollPane field instead.

ScrollPaneLayout

public ScrollPaneLayout()

addLayoutComponent

public void addLayoutComponent(String s,
                               Component c)

Adds the specified component to the layout. The layout is identified using one of:

• ScrollPaneConstants.VIEWPORT
• ScrollPaneConstants.VERTICAL_SCROLLBAR
• ScrollPaneConstants.HORIZONTAL_SCROLLBAR
• ScrollPaneConstants.ROW_HEADER
• ScrollPaneConstants.COLUMN_HEADER
• ScrollPaneConstants.LOWER_LEFT_CORNER
• ScrollPaneConstants.LOWER_RIGHT_CORNER
• ScrollPaneConstants.UPPER_LEFT_CORNER
• ScrollPaneConstants.UPPER_RIGHT_CORNER

Parameters:

s - the component identifier

c - the the component to be added

addSingletonComponent

protected Component addSingletonComponent(Component oldC,
                                          Component newC)

Removes an existing component. When a new component, such as the left corner, or vertical scrollbar, is added, the old one, if it exists, must be removed.

This method returns newC. If oldC is not equal to newC and is non-null, it will be removed from its parent.

Parameters:

oldC - the Component to replace

newC - the Component to add

Returns:

the newC

getColumnHeader

public JViewport getColumnHeader()

Returns the JViewport object that is the column header.

Returns:

the JViewport object that is the column header

getCorner

public Component getCorner(String key)

Returns the Component at the specified corner.

Parameters:

key - the String specifying the corner

Returns:

the Component at the specified corner, as defined in {@link ScrollPaneConstants}; if key is not one of the four corners, null is returned

getHorizontalScrollBar

public JScrollBar getHorizontalScrollBar()

Returns the JScrollBar object that handles horizontal scrolling.

Returns:

the JScrollBar object that handles horizontal scrolling

getHorizontalScrollBarPolicy

public int getHorizontalScrollBarPolicy()

Returns the horizontal scrollbar-display policy.

Returns:

an integer giving the display policy

getRowHeader

public JViewport getRowHeader()

Returns the JViewport object that is the row header.

Returns:

the JViewport object that is the row header

getVerticalScrollBar

public JScrollBar getVerticalScrollBar()

Returns the JScrollBar object that handles vertical scrolling.

Returns:

the JScrollBar object that handles vertical scrolling

getVerticalScrollBarPolicy

public int getVerticalScrollBarPolicy()

Returns the vertical scrollbar-display policy.

Returns:

an integer giving the display policy

getViewport

public JViewport getViewport()

Returns the JViewport object that displays the scrollable contents.

Returns:

the JViewport object that displays the scrollable contents

getViewportBorderBounds

public Rectangle getViewportBorderBounds(JScrollPane scrollpane)

Returns the bounds of the border around the specified scroll pane's viewport.

Parameters:

scrollpane

Returns:

the size and position of the viewport border

layoutContainer

public void layoutContainer(Container parent)

Lays out the scrollpane. The positioning of components depends on the following constraints:

• The row header, if present and visible, gets its preferred width and the viewport's height.
• The column header, if present and visible, gets its preferred height and the viewport's width.
• If a vertical scrollbar is needed, i.e. if the viewport's extent height is smaller than its view height or if the displayPolicy is ALWAYS, it's treated like the row header with respect to its dimensions and is made visible.
• If a horizontal scrollbar is needed, it is treated like the column header (see the paragraph above regarding the vertical scrollbar).
• If the scrollpane has a non-null viewportBorder, then space is allocated for that.
• The viewport gets the space available after accounting for the previous constraints.
• The corner components, if provided, are aligned with the ends of the scrollbars and headers. If there is a vertical scrollbar, the right corners appear; if there is a horizontal scrollbar, the lower corners appear; a row header gets left corners, and a column header gets upper corners.

Parameters:

parent - the Container to lay out

minimumLayoutSize

public Dimension minimumLayoutSize(Container parent)

The minimum size of a ScrollPane is the size of the insets plus minimum size of the viewport, plus the scrollpane's viewportBorder insets, plus the minimum size of the visible headers, plus the minimum size of the scrollbars whose displayPolicy isn't NEVER.

Parameters:

parent - the Container that will be laid out

Returns:

a Dimension object specifying the minimum size

preferredLayoutSize

public Dimension preferredLayoutSize(Container parent)

The preferred size of a ScrollPane is the size of the insets, plus the preferred size of the viewport, plus the preferred size of the visible headers, plus the preferred size of the scrollbars that will appear given the current view and the current scrollbar displayPolicies.

Note that the rowHeader is calculated as part of the preferred width and the colHeader is calculated as part of the preferred size.

Parameters:

parent - the Container that will be laid out

Returns:

a Dimension object specifying the preferred size of the viewport and any scrollbars

removeLayoutComponent

public void removeLayoutComponent(Component c)

Removes the specified component from the layout.

Parameters:

c - the component to remove

setHorizontalScrollBarPolicy

public void setHorizontalScrollBarPolicy(int x)

Sets the horizontal scrollbar-display policy. The options are:

• ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED
• ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER
• ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS

Note: Applications should use the JScrollPane version of this method. It only exists for backwards compatibility with the Swing 1.0.2 (and earlier) versions of this class.

Parameters:

x - an int giving the display policy

setVerticalScrollBarPolicy

public void setVerticalScrollBarPolicy(int x)

Sets the vertical scrollbar-display policy. The options are:

• ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED
• ScrollPaneConstants.VERTICAL_SCROLLBAR_NEVER
• ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS

Note: Applications should use the JScrollPane version of this method. It only exists for backwards compatibility with the Swing 1.0.2 (and earlier) versions of this class.

Parameters:

x - an integer giving the display policy

syncWithScrollPane

public void syncWithScrollPane(JScrollPane sp)

This method is invoked after the ScrollPaneLayout is set as the LayoutManager of a JScrollPane. It initializes all of the internal fields that are ordinarily set by addLayoutComponent. For example:

 ScrollPaneLayout mySPLayout = new ScrollPanelLayout() {
     public void layoutContainer(Container p) {
         super.layoutContainer(p);
         // do some extra work here ...
     }
 };
 scrollpane.setLayout(mySPLayout):
 

Parameters:

sp