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/OpenJDK 21

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 has been added to the java.beans package. Please see XMLEncoder.

Since:
1.2
See Also:

Nested Class Summary

Modifier and Type Class Description
static class  ScrollPaneLayout.UIResource
The UI resource version of ScrollPaneLayout.

Field Summary

Modifier and Type Field Description
protected JViewport colHead
The column header child.
protected JScrollBar hsb
The scrollpane's horizontal scrollbar child.
protected int hsbPolicy
The display policy for the horizontal scrollbar.
protected Component lowerLeft
The component to display in the lower left corner.
protected Component lowerRight
The component to display in the lower right corner.
protected JViewport rowHead
The row header child.
protected Component upperLeft
The component to display in the upper left corner.
protected Component upperRight
The component to display in the upper right corner.
protected JViewport viewport
The scrollpane's viewport child.
protected JScrollBar vsb
The scrollpane's vertical scrollbar child.
protected int vsbPolicy
The display policy for 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
ScrollPaneLayout()
Constructs a ScrollPaneLayout.

Method Summary

Modifier and Type Method Description
void addLayoutComponent(String s, Component c)
Adds the specified component to the layout.
protected Component addSingletonComponent(Component oldC, Component newC)
Removes an existing component.
JViewport getColumnHeader()
Returns the JViewport object that is the column header.
Component getCorner(String key)
Returns the Component at the specified corner.
JScrollBar getHorizontalScrollBar()
Returns the JScrollBar object that handles horizontal scrolling.
int getHorizontalScrollBarPolicy()
Returns the horizontal scrollbar-display policy.
JViewport getRowHeader()
Returns the JViewport object that is the row header.
JScrollBar getVerticalScrollBar()
Returns the JScrollBar object that handles vertical scrolling.
int getVerticalScrollBarPolicy()
Returns the vertical scrollbar-display policy.
JViewport getViewport()
Returns the JViewport object that displays the scrollable contents.
Rectangle getViewportBorderBounds(JScrollPane scrollpane)
Deprecated.
As of JDK version Swing1.1 replaced by JScrollPane.getViewportBorderBounds().
void layoutContainer(Container parent)
Lays out the scrollpane.
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.
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.
void removeLayoutComponent(Component c)
Removes the specified component from the layout.
void setHorizontalScrollBarPolicy(int x)
Sets the horizontal scrollbar-display policy.
void setVerticalScrollBarPolicy(int x)
Sets the vertical scrollbar-display policy.
void syncWithScrollPane(JScrollPane sp)
This method is invoked after the ScrollPaneLayout is set as the LayoutManager of a JScrollPane.

Methods declared in class java.lang.Object

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

Field Details

viewport

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

protected JScrollBar vsb
The scrollpane's vertical scrollbar child. Default is a JScrollBar.
See Also:

hsb

protected JScrollBar hsb
The scrollpane's horizontal scrollbar child. Default is a JScrollBar.
See Also:

rowHead

protected JViewport rowHead
The row header child. Default is null.
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colHead

protected JViewport colHead
The column header child. Default is null.
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lowerLeft

protected Component lowerLeft
The component to display in the lower left corner. Default is null.
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lowerRight

protected Component lowerRight
The component to display in the lower right corner. Default is null.
See Also:

upperLeft

protected Component upperLeft
The component to display in the upper left corner. Default is null.
See Also:

upperRight

protected Component upperRight
The component to display in the upper right corner. Default is null.
See Also:

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.

See Also:

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.

See Also:

Constructor Details

ScrollPaneLayout

public ScrollPaneLayout()
Constructs a ScrollPaneLayout.

Method Details

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 - an instance of the JScrollPane

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

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
Specified by:
addLayoutComponent in interface LayoutManager
Parameters:
s - the component identifier
c - the component to be added
Throws:
IllegalArgumentException - if s is an invalid key

removeLayoutComponent

public void removeLayoutComponent(Component c)
Removes the specified component from the layout.
Specified by:
removeLayoutComponent in interface LayoutManager
Parameters:
c - the component to remove

getVerticalScrollBarPolicy

public int getVerticalScrollBarPolicy()
Returns the vertical scrollbar-display policy.
Returns:
an integer giving the display policy
See Also:

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
Throws:
IllegalArgumentException - if x is an invalid vertical scroll bar policy, as listed above

getHorizontalScrollBarPolicy

public int getHorizontalScrollBarPolicy()
Returns the horizontal scrollbar-display policy.
Returns:
an integer giving the display policy
See Also:

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
Throws:
IllegalArgumentException - if x is not a valid horizontal scrollbar policy, as listed above

getViewport

public JViewport getViewport()
Returns the JViewport object that displays the scrollable contents.
Returns:
the JViewport object that displays the scrollable contents
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getHorizontalScrollBar

public JScrollBar getHorizontalScrollBar()
Returns the JScrollBar object that handles horizontal scrolling.
Returns:
the JScrollBar object that handles horizontal scrolling
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getVerticalScrollBar

public JScrollBar getVerticalScrollBar()
Returns the JScrollBar object that handles vertical scrolling.
Returns:
the JScrollBar object that handles vertical scrolling
See Also:

getRowHeader

public JViewport getRowHeader()
Returns the JViewport object that is the row header.
Returns:
the JViewport object that is the row header
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getColumnHeader

public JViewport getColumnHeader()
Returns the JViewport object that is the column header.
Returns:
the JViewport object that is the column header
See Also:

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 ScrollPaneConstants; if key is not one of the four corners, null is returned
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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.

Specified by:
preferredLayoutSize in interface LayoutManager
Parameters:
parent - the Container that will be laid out
Returns:
a Dimension object specifying the preferred size of the viewport and any scrollbars
See Also:

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.
Specified by:
minimumLayoutSize in interface LayoutManager
Parameters:
parent - the Container that will be laid out
Returns:
a Dimension object specifying the minimum size
See Also:

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.
Specified by:
layoutContainer in interface LayoutManager
Parameters:
parent - the Container to lay out

getViewportBorderBounds

@Deprecated public Rectangle getViewportBorderBounds(JScrollPane scrollpane)
Deprecated.
As of JDK version Swing1.1 replaced by JScrollPane.getViewportBorderBounds().
Returns the bounds of the border around the specified scroll pane's viewport.
Parameters:
scrollpane - an instance of the JScrollPane
Returns:
the size and position of the viewport border

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.desktop/javax/swing/ScrollPaneLayout.html