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Chapter 19 java.awt Reference |
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ScrollPane 
Name
ScrollPane
![[Graphic: Figure from the text]](./figs/scroll2.gif)
Description
The ScrollPane class provides automatic scrolling of a child component.
Class Definition
public class java.awt.ScrollPane
extends java.awt.Container {
// Constants
public final static int SCROLLBARS_ALWAYS;
public final static int SCROLLBARS_AS_NEEDED;
public final static int SCROLLBARS_NEVER;
// Constructors
public ScrollPane();
public ScrollPane (int scrollbarDisplayPolicy);
// Public Instance Methods
public void addNotify();
public void doLayout();
public Adjustable getHAdjustable();
public int getHScrollbarHeight();
public Point getScrollPosition();
public int getScrollbarDisplayPolicy();
public Adjustable getVAdjustable();
public int getVScrollbarWidth();
public Dimension getViewportSize();
public void layout(); 
public String paramString();
public void printComponents (Graphics g);
public final void setLayout (LayoutManager mgr);
public void setScrollPosition (int x, int y);
public void setScrollPosition (Point p);
//Protected Instance Methods
protected final void addImpl (Component comp, Object constraints,
int index);
}
Constants
SCROLLBARS_ALWAYS
public final static int SCROLLBARS_ALWAYS
Always show the scrollbars.
SCROLLBARS_AS_NEEDED
public final static int SCROLLBARS_AS_NEEDED
Only show the scrollbars if the contents of the ScrollPane are larger than what is visible.
SCROLLBARS_NEVER
public final static int SCROLLBARS_NEVER
Don't ever show the scrollbars. The ScrollPane can still be scrolled programmatically.
Constructors
ScrollPane
public ScrollPane()
- Description
-
Constructs a ScrollPane object with SCROLLBARS_AS_NEEDED.
public ScrollPane (int scrollbarDisplayPolicy)
- Parameters
-
- scrollbarDisplayPolicy
-
One of the SCROLLBARS_ constants.
- scrollbarDisplayPolicy
- Description
-
Constructs a ScrollPane object with the specified scrollbar display policy.
Instance Methods
addImpl
protected final void addImpl (Component comp, Object constraints, int index)
- Parameters
-
- comp
-
The component to add to the Scrollpane.
- constraints
-
Layout constraints; ignored.
- index
-
The position at which to add the component; should always be less than or equal to 0.
- comp
- Returns
-
The component that was added.
- Overrides
-
Container.addImpl (Component, Object, int)
- Throws
-
- IllegalArgumentException
-
If pos is greater than 0.
- IllegalArgumentException
- Description
-
Adds a child component to the Scrollpane. If there already was a child component, it is replaced by the new component.
addNotify
public void addNotify()
- Overrides
-
Container.addNotify()
- Description
-
Creates ScrollPane's peer.
doLayout
public void doLayout()
- Overrides
-
Container.doLayout()
- Description
-
Lays out the ScrollPane. Resizes the child component to its preferred size.
getHAdjustable
public Adjustable getHAdjustable()
- Returns
-
The object implementing the Adjustable interface that is used to adjust the ScrollPane horizontally. Usually this is a Scrollbar.
getHScrollbarHeight
public int getHScrollbarHeight()
- Returns
-
The height a horizontal scrollbar would occupy, regardless of whether it's shown or not.
getScrollPosition
public Point getScrollPosition()
- Returns
-
Returns the position within the child component that is displayed at 0, 0 in the ScrollPane.
getScrollbarDisplayPolicy
public int getScrollbarDisplayPolicy()
- Returns
-
The display policy for the scrollbars (one of the SCROLLBARS_ constants).
getVAdjustable
public Adjustable getVAdjustable()
- Returns
-
The object implementing the Adjustable interface that is used to adjust the ScrollPane vertically. Usually this is a Scrollbar.
getVScrollbarWidth
public int getVScrollbarWidth()
- Returns
-
The width a vertical scrollbar would occupy, regardless of whether it's shown or not.
getViewportSize
public Dimension getViewportSize()
- Returns
-
The size of the ScrollPane's port (the area of the child component that is shown).
layout
public void layout()
- Overrides
-
Container.layout()
- Description
-
Lays out component. Replaced by doLayout().
paramString
public String paramString()
- Returns
-
String with current settings of ScrollPane.
- Overrides
-
Container.paramString()
- Description
-
Helper method for toString() to generate string of current settings.
printComponents
public void printComponents (Graphics g)
- Parameters
-
- g
-
Graphics context.
- g
- Overrides
-
Container.printComponents(Graphics)
- Description
-
Prints the ScrollPane's child component.
setLayout
public void setLayout (LayoutManager manager)
- Parameters
-
- manager
-
Ignored.
- manager
- Overrides
-
Container.setLayout(LayoutManager)
- Description
-
Does nothing. No layout manager is needed because there is only one child component.
setScrollPosition
public void setScrollPosition (int x, int y)
- Parameters
-
- x
-
New horizontal position.
- y
-
New vertical position.
- x
- Throws
-
- IllegalArgumentException
-
If the point given is not valid.
- IllegalArgumentException
- Description
-
Scroll to the given position in the child component.
public void setScrollPosition (Point p)
- Parameters
-
- p
-
New position.
- p
- Throws
-
- IllegalArgumentException
-
If the point given is not valid.
- IllegalArgumentException
- Description
-
Scroll to the given position in the child component.
See Also
Adjustable, Container, Point, Scrollbar
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| Rectangle |  |
Scrollbar |
