public class

JScrollPane

extends JComponent
implements Accessible ScrollPaneConstants
java.lang.Object
   ↳ java.awt.Component
     ↳ java.awt.Container
       ↳ javax.swing.JComponent
         ↳ javax.swing.JScrollPane

Class Overview

Provides a scrollable view of a lightweight component. A JScrollPane manages a viewport, optional vertical and horizontal scroll bars, and optional row and column heading viewports. You can find task-oriented documentation of JScrollPane in How to Use Scroll Panes, a section in The Java Tutorial. Note that JScrollPane does not support heavyweight components.

The following text describes this image.

The JViewport provides a window, or "viewport" onto a data source -- for example, a text file. That data source is the "scrollable client" (aka data model) displayed by the JViewport view. A JScrollPane basically consists of JScrollBars, a JViewport, and the wiring between them, as shown in the diagram at right.

In addition to the scroll bars and viewport, a JScrollPane can have a column header and a row header. Each of these is a JViewport object that you specify with setRowHeaderView, and setColumnHeaderView. The column header viewport automatically scrolls left and right, tracking the left-right scrolling of the main viewport. (It never scrolls vertically, however.) The row header acts in a similar fashion.

Where two scroll bars meet, the row header meets the column header, or a scroll bar meets one of the headers, both components stop short of the corner, leaving a rectangular space which is, by default, empty. These spaces can potentially exist in any number of the four corners. In the previous diagram, the top right space is present and identified by the label "corner component".

Any number of these empty spaces can be replaced by using the setCorner method to add a component to a particular corner. (Note: The same component cannot be added to multiple corners.) This is useful if there's some extra decoration or function you'd like to add to the scroll pane. The size of each corner component is entirely determined by the size of the headers and/or scroll bars that surround it.

A corner component will only be visible if there is an empty space in that corner for it to exist in. For example, consider a component set into the top right corner of a scroll pane with a column header. If the scroll pane's vertical scrollbar is not present, perhaps because the view component hasn't grown large enough to require it, then the corner component will not be shown (since there is no empty space in that corner created by the meeting of the header and vertical scroll bar). Forcing the scroll bar to always be shown, using setVerticalScrollBarPolicy(VERTICAL_SCROLLBAR_ALWAYS), will ensure that the space for the corner component always exists.

To add a border around the main viewport, you can use setViewportBorder. (Of course, you can also add a border around the whole scroll pane using setBorder.)

A common operation to want to do is to set the background color that will be used if the main viewport view is smaller than the viewport, or is not opaque. This can be accomplished by setting the background color of the viewport, via scrollPane.getViewport().setBackground(). The reason for setting the color of the viewport and not the scrollpane is that by default JViewport is opaque which, among other things, means it will completely fill in its background using its background color. Therefore when JScrollPane draws its background the viewport will usually draw over it.

By default JScrollPane uses ScrollPaneLayout to handle the layout of its child Components. ScrollPaneLayout determines the size to make the viewport view in one of two ways:

  1. If the view implements Scrollable a combination of getPreferredScrollableViewportSize, getScrollableTracksViewportWidth and getScrollableTracksViewportHeightis used, otherwise
  2. getPreferredSize is used.

Warning: Swing is not thread safe. For more information see Swing's Threading Policy.

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

Summary

Nested Classes
class JScrollPane.AccessibleJScrollPane This class implements accessibility support for the JScrollPane class. 
class JScrollPane.ScrollBar By default JScrollPane creates scrollbars that are instances of this class. 
[Expand]
Inherited Constants
From class javax.swing.JComponent
From class java.awt.Component
From interface java.awt.image.ImageObserver
From interface javax.swing.ScrollPaneConstants
Fields
protected JViewport columnHeader The column header child.
protected JScrollBar horizontalScrollBar The scrollpane's horizontal scrollbar child.
protected int horizontalScrollBarPolicy 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 rowHeader 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 JScrollBar verticalScrollBar The scrollpane's vertical scrollbar child.
protected int verticalScrollBarPolicy The display policy for the vertical scrollbar.
protected JViewport viewport The scrollpane's viewport child.
[Expand]
Inherited Fields
From class javax.swing.JComponent
Public Constructors
JScrollPane(Component view, int vsbPolicy, int hsbPolicy)
Creates a JScrollPane that displays the view component in a viewport whose view position can be controlled with a pair of scrollbars.
JScrollPane(Component view)
Creates a JScrollPane that displays the contents of the specified component, where both horizontal and vertical scrollbars appear whenever the component's contents are larger than the view.
JScrollPane(int vsbPolicy, int hsbPolicy)
Creates an empty (no viewport view) JScrollPane with specified scrollbar policies.
JScrollPane()
Creates an empty (no viewport view) JScrollPane where both horizontal and vertical scrollbars appear when needed.
Public Methods
JScrollBar createHorizontalScrollBar()
Returns a JScrollPane.ScrollBar by default.
JScrollBar createVerticalScrollBar()
Returns a JScrollPane.ScrollBar by default.
AccessibleContext getAccessibleContext()
Gets the AccessibleContext associated with this JScrollPane.
JViewport getColumnHeader()
Returns the column header.
Component getCorner(String key)
Returns the component at the specified corner.
JScrollBar getHorizontalScrollBar()
Returns the horizontal scroll bar that controls the viewport's horizontal view position.
int getHorizontalScrollBarPolicy()
Returns the horizontal scroll bar policy value.
JViewport getRowHeader()
Returns the row header.
ScrollPaneUI getUI()
Returns the look and feel (L&F) object that renders this component.
String getUIClassID()
Returns the suffix used to construct the name of the L&F class used to render this component.
JScrollBar getVerticalScrollBar()
Returns the vertical scroll bar that controls the viewports vertical view position.
int getVerticalScrollBarPolicy()
Returns the vertical scroll bar policy value.
JViewport getViewport()
Returns the current JViewport.
Border getViewportBorder()
Returns the Border object that surrounds the viewport.
Rectangle getViewportBorderBounds()
Returns the bounds of the viewport's border.
boolean isValidateRoot()
Overridden to return true so that any calls to revalidate on any descendants of this JScrollPane will cause the entire tree beginning with this JScrollPane to be validated.
boolean isWheelScrollingEnabled()
Indicates whether or not scrolling will take place in response to the mouse wheel.
void setColumnHeader(JViewport columnHeader)
Removes the old columnHeader, if it exists; if the new columnHeader isn't null, syncs the x coordinate of its viewPosition with the viewport (if there is one) and then adds it to the scroll pane.
void setColumnHeaderView(Component view)
Creates a column-header viewport if necessary, sets its view, and then adds the column-header viewport to the scrollpane.
void setComponentOrientation(ComponentOrientation co)
Sets the orientation for the vertical and horizontal scrollbars as determined by the ComponentOrientation argument.
void setCorner(String key, Component corner)
Adds a child that will appear in one of the scroll panes corners, if there's room.
void setHorizontalScrollBar(JScrollBar horizontalScrollBar)
Adds the scrollbar that controls the viewport's horizontal view position to the scrollpane.
void setHorizontalScrollBarPolicy(int policy)
Determines when the horizontal scrollbar appears in the scrollpane.
void setLayout(LayoutManager layout)
Sets the layout manager for this JScrollPane.
void setRowHeader(JViewport rowHeader)
Removes the old rowHeader, if it exists; if the new rowHeader isn't null, syncs the y coordinate of its viewPosition with the viewport (if there is one) and then adds it to the scroll pane.
void setRowHeaderView(Component view)
Creates a row-header viewport if necessary, sets its view and then adds the row-header viewport to the scrollpane.
void setUI(ScrollPaneUI ui)
Sets the ScrollPaneUI object that provides the look and feel (L&F) for this component.
void setVerticalScrollBar(JScrollBar verticalScrollBar)
Adds the scrollbar that controls the viewports vertical view position to the scrollpane.
void setVerticalScrollBarPolicy(int policy)
Determines when the vertical scrollbar appears in the scrollpane.
void setViewport(JViewport viewport)
Removes the old viewport (if there is one); forces the viewPosition of the new viewport to be in the +x,+y quadrant; syncs up the row and column headers (if there are any) with the new viewport; and finally syncs the scrollbars and headers with the new viewport.
void setViewportBorder(Border viewportBorder)
Adds a border around the viewport.
void setViewportView(Component view)
Creates a viewport if necessary and then sets its view.
void setWheelScrollingEnabled(boolean handleWheel)
Enables/disables scrolling in response to movement of the mouse wheel.
void updateUI()
Replaces the current ScrollPaneUI object with a version from the current default look and feel.
Protected Methods
JViewport createViewport()
Returns a new JViewport by default.
String paramString()
Returns a string representation of this JScrollPane.
[Expand]
Inherited Methods
From class javax.swing.JComponent
From class java.awt.Container
From class java.awt.Component
From class java.lang.Object
From interface java.awt.MenuContainer
From interface java.awt.image.ImageObserver
From interface javax.accessibility.Accessible

Fields

protected JViewport columnHeader

The column header child. Default is null.

protected JScrollBar horizontalScrollBar

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

protected int horizontalScrollBarPolicy

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

protected Component lowerLeft

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

protected Component lowerRight

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

protected JViewport rowHeader

The row header child. Default is null.

protected Component upperLeft

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

protected Component upperRight

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

protected JScrollBar verticalScrollBar

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

protected int verticalScrollBarPolicy

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

protected JViewport viewport

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

Public Constructors

public JScrollPane (Component view, int vsbPolicy, int hsbPolicy)

Creates a JScrollPane that displays the view component in a viewport whose view position can be controlled with a pair of scrollbars. The scrollbar policies specify when the scrollbars are displayed, For example, if vsbPolicy is VERTICAL_SCROLLBAR_AS_NEEDED then the vertical scrollbar only appears if the view doesn't fit vertically. The available policy settings are listed at setVerticalScrollBarPolicy(int) and setHorizontalScrollBarPolicy(int).

Parameters
view the component to display in the scrollpanes viewport
vsbPolicy an integer that specifies the vertical scrollbar policy
hsbPolicy an integer that specifies the horizontal scrollbar policy

public JScrollPane (Component view)

Creates a JScrollPane that displays the contents of the specified component, where both horizontal and vertical scrollbars appear whenever the component's contents are larger than the view.

Parameters
view the component to display in the scrollpane's viewport

public JScrollPane (int vsbPolicy, int hsbPolicy)

Creates an empty (no viewport view) JScrollPane with specified scrollbar policies. The available policy settings are listed at setVerticalScrollBarPolicy(int) and setHorizontalScrollBarPolicy(int).

Parameters
vsbPolicy an integer that specifies the vertical scrollbar policy
hsbPolicy an integer that specifies the horizontal scrollbar policy

public JScrollPane ()

Creates an empty (no viewport view) JScrollPane where both horizontal and vertical scrollbars appear when needed.

Public Methods

public JScrollBar createHorizontalScrollBar ()

Returns a JScrollPane.ScrollBar by default. Subclasses may override this method to force ScrollPaneUI implementations to use a JScrollBar subclass. Used by ScrollPaneUI implementations to create the horizontal scrollbar.

Returns
  • a JScrollBar with a horizontal orientation
See Also

public JScrollBar createVerticalScrollBar ()

Returns a JScrollPane.ScrollBar by default. Subclasses may override this method to force ScrollPaneUI implementations to use a JScrollBar subclass. Used by ScrollPaneUI implementations to create the vertical scrollbar.

Returns
  • a JScrollBar with a vertical orientation
See Also

public AccessibleContext getAccessibleContext ()

Gets the AccessibleContext associated with this JScrollPane. For scroll panes, the AccessibleContext takes the form of an AccessibleJScrollPane. A new AccessibleJScrollPane instance is created if necessary.

Returns
  • an AccessibleJScrollPane that serves as the AccessibleContext of this JScrollPane

public JViewport getColumnHeader ()

Returns the column header.

Returns
  • the columnHeader property

public Component getCorner (String key)

Returns the component at the specified corner. The key value specifying the corner is one of:

  • ScrollPaneConstants.LOWER_LEFT_CORNER
  • ScrollPaneConstants.LOWER_RIGHT_CORNER
  • ScrollPaneConstants.UPPER_LEFT_CORNER
  • ScrollPaneConstants.UPPER_RIGHT_CORNER
  • ScrollPaneConstants.LOWER_LEADING_CORNER
  • ScrollPaneConstants.LOWER_TRAILING_CORNER
  • ScrollPaneConstants.UPPER_LEADING_CORNER
  • ScrollPaneConstants.UPPER_TRAILING_CORNER

Parameters
key one of the values as shown above
Returns
  • the corner component (which may be null) identified by the given key, or null if the key is invalid

public JScrollBar getHorizontalScrollBar ()

Returns the horizontal scroll bar that controls the viewport's horizontal view position.

Returns
  • the horizontalScrollBar property

public int getHorizontalScrollBarPolicy ()

Returns the horizontal scroll bar policy value.

Returns
  • the horizontalScrollBarPolicy property

public JViewport getRowHeader ()

Returns the row header.

Returns
  • the rowHeader property

public ScrollPaneUI getUI ()

Returns the look and feel (L&F) object that renders this component.

Returns
  • the ScrollPaneUI object that renders this component

public String getUIClassID ()

Returns the suffix used to construct the name of the L&F class used to render this component.

Returns
  • the string "ScrollPaneUI"

public JScrollBar getVerticalScrollBar ()

Returns the vertical scroll bar that controls the viewports vertical view position.

Returns
  • the verticalScrollBar property

public int getVerticalScrollBarPolicy ()

Returns the vertical scroll bar policy value.

Returns
  • the verticalScrollBarPolicy property

public JViewport getViewport ()

Returns the current JViewport.

Returns
  • the viewport property

public Border getViewportBorder ()

Returns the Border object that surrounds the viewport.

Returns
  • the viewportBorder property

public Rectangle getViewportBorderBounds ()

Returns the bounds of the viewport's border.

Returns
  • a Rectangle object specifying the viewport border

public boolean isValidateRoot ()

Overridden to return true so that any calls to revalidate on any descendants of this JScrollPane will cause the entire tree beginning with this JScrollPane to be validated.

Returns
  • true

public boolean isWheelScrollingEnabled ()

Indicates whether or not scrolling will take place in response to the mouse wheel. Wheel scrolling is enabled by default.

public void setColumnHeader (JViewport columnHeader)

Removes the old columnHeader, if it exists; if the new columnHeader isn't null, syncs the x coordinate of its viewPosition with the viewport (if there is one) and then adds it to the scroll pane.

Most applications will find it more convenient to use setColumnHeaderView to add a column header component and its viewport to the scroll pane.

public void setColumnHeaderView (Component view)

Creates a column-header viewport if necessary, sets its view, and then adds the column-header viewport to the scrollpane. For example:

 JScrollPane scrollpane = new JScrollPane();
 scrollpane.setViewportView(myBigComponentToScroll);
 scrollpane.setColumnHeaderView(myBigComponentsColumnHeader);
 

Parameters
view the component to display as the column header

public void setComponentOrientation (ComponentOrientation co)

Sets the orientation for the vertical and horizontal scrollbars as determined by the ComponentOrientation argument.

Parameters
co one of the following values:
  • java.awt.ComponentOrientation.LEFT_TO_RIGHT
  • java.awt.ComponentOrientation.RIGHT_TO_LEFT
  • java.awt.ComponentOrientation.UNKNOWN

public void setCorner (String key, Component corner)

Adds a child that will appear in one of the scroll panes corners, if there's room. For example with both scrollbars showing (on the right and bottom edges of the scrollpane) the lower left corner component will be shown in the space between ends of the two scrollbars. Legal values for the key are:

  • ScrollPaneConstants.LOWER_LEFT_CORNER
  • ScrollPaneConstants.LOWER_RIGHT_CORNER
  • ScrollPaneConstants.UPPER_LEFT_CORNER
  • ScrollPaneConstants.UPPER_RIGHT_CORNER
  • ScrollPaneConstants.LOWER_LEADING_CORNER
  • ScrollPaneConstants.LOWER_TRAILING_CORNER
  • ScrollPaneConstants.UPPER_LEADING_CORNER
  • ScrollPaneConstants.UPPER_TRAILING_CORNER

Although "corner" doesn't match any beans property signature, PropertyChange events are generated with the property name set to the corner key.

Parameters
key identifies which corner the component will appear in
corner one of the following components:
  • lowerLeft
  • lowerRight
  • upperLeft
  • upperRight
Throws
IllegalArgumentException if corner key is invalid

public void setHorizontalScrollBar (JScrollBar horizontalScrollBar)

Adds the scrollbar that controls the viewport's horizontal view position to the scrollpane. This is usually unnecessary, as JScrollPane creates horizontal and vertical scrollbars by default.

Parameters
horizontalScrollBar the horizontal scrollbar to be added

public void setHorizontalScrollBarPolicy (int policy)

Determines when the horizontal scrollbar appears in the scrollpane. The options are:

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

Parameters
policy one of the three values listed above
Throws
IllegalArgumentException if policy is not one of the legal values shown above

public void setLayout (LayoutManager layout)

Sets the layout manager for this JScrollPane. This method overrides setLayout in java.awt.Container to ensure that only LayoutManagers which are subclasses of ScrollPaneLayout can be used in a JScrollPane. If layout is non-null, this will invoke syncWithScrollPane on it.

Parameters
layout the specified layout manager
Throws
ClassCastException if layout is not a ScrollPaneLayout

public void setRowHeader (JViewport rowHeader)

Removes the old rowHeader, if it exists; if the new rowHeader isn't null, syncs the y coordinate of its viewPosition with the viewport (if there is one) and then adds it to the scroll pane.

Most applications will find it more convenient to use setRowHeaderView to add a row header component and its viewport to the scroll pane.

Parameters
rowHeader the new row header to be used; if null the old row header is still removed and the new rowHeader is set to null

public void setRowHeaderView (Component view)

Creates a row-header viewport if necessary, sets its view and then adds the row-header viewport to the scrollpane. For example:

 JScrollPane scrollpane = new JScrollPane();
 scrollpane.setViewportView(myBigComponentToScroll);
 scrollpane.setRowHeaderView(myBigComponentsRowHeader);
 

Parameters
view the component to display as the row header

public void setUI (ScrollPaneUI ui)

Sets the ScrollPaneUI object that provides the look and feel (L&F) for this component.

Parameters
ui the ScrollPaneUI L&F object
See Also

public void setVerticalScrollBar (JScrollBar verticalScrollBar)

Adds the scrollbar that controls the viewports vertical view position to the scrollpane. This is usually unnecessary, as JScrollPane creates vertical and horizontal scrollbars by default.

Parameters
verticalScrollBar the new vertical scrollbar to be added

public void setVerticalScrollBarPolicy (int policy)

Determines when the vertical scrollbar appears in the scrollpane. Legal values are:

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

Parameters
policy one of the three values listed above
Throws
IllegalArgumentException if policy is not one of the legal values shown above

public void setViewport (JViewport viewport)

Removes the old viewport (if there is one); forces the viewPosition of the new viewport to be in the +x,+y quadrant; syncs up the row and column headers (if there are any) with the new viewport; and finally syncs the scrollbars and headers with the new viewport.

Most applications will find it more convenient to use setViewportView to add a viewport and a view to the scrollpane.

Parameters
viewport the new viewport to be used; if viewport is null, the old viewport is still removed and the new viewport is set to null

public void setViewportBorder (Border viewportBorder)

Adds a border around the viewport. Note that the border isn't set on the viewport directly, JViewport doesn't support the JComponent border property. Similarly setting the JScrollPanes viewport doesn't affect the viewportBorder property.

The default value of this property is computed by the look and feel implementation.

Parameters
viewportBorder the border to be added

public void setViewportView (Component view)

Creates a viewport if necessary and then sets its view. Applications that don't provide the view directly to the JScrollPane constructor should use this method to specify the scrollable child that's going to be displayed in the scrollpane. For example:

 JScrollPane scrollpane = new JScrollPane();
 scrollpane.setViewportView(myBigComponentToScroll);
 
Applications should not add children directly to the scrollpane.

Parameters
view the component to add to the viewport

public void setWheelScrollingEnabled (boolean handleWheel)

Enables/disables scrolling in response to movement of the mouse wheel. Wheel scrolling is enabled by default.

Parameters
handleWheel true if scrolling should be done automatically for a MouseWheelEvent, false otherwise.

public void updateUI ()

Replaces the current ScrollPaneUI object with a version from the current default look and feel. To be called when the default look and feel changes.

Protected Methods

protected JViewport createViewport ()

Returns a new JViewport by default. Used to create the viewport (as needed) in setViewportView, setRowHeaderView, and setColumnHeaderView. Subclasses may override this method to return a subclass of JViewport.

Returns
  • a new JViewport

protected String paramString ()

Returns a string representation of this JScrollPane. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be null.

Returns
  • a string representation of this JScrollPane.