FileDocCategorySizeDatePackage
ViewportLayout.javaAPI DocJava SE 5 API6051Fri Aug 26 14:58:00 BST 2005javax.swing

ViewportLayout

public class ViewportLayout extends Object implements Serializable, LayoutManager
The default layout manager for JViewport. ViewportLayout defines a policy for layout that should be useful for most applications. The viewport makes its view the same size as the viewport, however it will not make the view smaller than its minimum size. As the viewport grows the view is kept bottom justified until the entire view is visible, subsequently the view is kept top justified.

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 {@link java.beans.XMLEncoder}.

version
1.38 12/19/03
author
Hans Muller

Fields Summary
static ViewportLayout
SHARED_INSTANCE
Constructors Summary
Methods Summary
public voidaddLayoutComponent(java.lang.String name, java.awt.Component c)
Adds the specified component to the layout. Not used by this class.

param
name the name of the component
param
c the the component to be added
public voidlayoutContainer(java.awt.Container parent)
Called by the AWT when the specified container needs to be laid out.

param
parent the container to lay out
exception
AWTError if the target isn't the container specified to the BoxLayout constructor

	JViewport vp = (JViewport)parent;
	Component view = vp.getView();
	Scrollable scrollableView = null;

	if (view == null) {
	    return;
	}
	else if (view instanceof Scrollable) {
	    scrollableView = (Scrollable) view;
	}

	/* All of the dimensions below are in view coordinates, except
	 * vpSize which we're converting.
	 */

	Insets insets = vp.getInsets();
	Dimension viewPrefSize = view.getPreferredSize();
	Dimension vpSize = vp.getSize();
	Dimension extentSize = vp.toViewCoordinates(vpSize);
	Dimension viewSize = new Dimension(viewPrefSize);

	if (scrollableView != null) {
	    if (scrollableView.getScrollableTracksViewportWidth()) {
		viewSize.width = vpSize.width;
	    }
	    if (scrollableView.getScrollableTracksViewportHeight()) {
		viewSize.height = vpSize.height;
	    }
	}

	Point viewPosition = vp.getViewPosition();

	/* If the new viewport size would leave empty space to the
	 * right of the view, right justify the view or left justify
	 * the view when the width of the view is smaller than the
	 * container.
	 */
	if (scrollableView == null ||
	    vp.getParent() == null ||
	    vp.getParent().getComponentOrientation().isLeftToRight()) {
	    if ((viewPosition.x + extentSize.width) > viewSize.width) {
		viewPosition.x = Math.max(0, viewSize.width - extentSize.width);
	    }
	} else {
	    if (extentSize.width > viewSize.width) {
		viewPosition.x = viewSize.width - extentSize.width;
	    } else {
		viewPosition.x = Math.max(0, Math.min(viewSize.width - extentSize.width, viewPosition.x));
	    }
	}

	/* If the new viewport size would leave empty space below the
	 * view, bottom justify the view or top justify the view when
	 * the height of the view is smaller than the container.
	 */
	if ((viewPosition.y + extentSize.height) > viewSize.height) {
	    viewPosition.y = Math.max(0, viewSize.height - extentSize.height);
	}

	/* If we haven't been advised about how the viewports size 
	 * should change wrt to the viewport, i.e. if the view isn't
	 * an instance of Scrollable, then adjust the views size as follows.
	 * 
	 * If the origin of the view is showing and the viewport is
	 * bigger than the views preferred size, then make the view
	 * the same size as the viewport.
	 */
	if (scrollableView == null) {
            if ((viewPosition.x == 0) && (vpSize.width > viewPrefSize.width)) {
        	viewSize.width = vpSize.width;
            }
            if ((viewPosition.y == 0) && (vpSize.height > viewPrefSize.height)) {
        	viewSize.height = vpSize.height;
            }
        }
	vp.setViewPosition(viewPosition);
	vp.setViewSize(viewSize);
public java.awt.DimensionminimumLayoutSize(java.awt.Container parent)
Returns the minimum dimensions needed to layout the components contained in the specified target container.

param
parent the component which needs to be laid out
return
a Dimension object containing the minimum dimensions
see
#preferredLayoutSize

	return new Dimension(4, 4);
public java.awt.DimensionpreferredLayoutSize(java.awt.Container parent)
Returns the preferred dimensions for this layout given the components in the specified target container.

param
parent the component which needs to be laid out
return
a Dimension object containing the preferred dimensions
see
#minimumLayoutSize

	Component view = ((JViewport)parent).getView();
	if (view == null) {
	    return new Dimension(0, 0);
	}
	else if (view instanceof Scrollable) {
	    return ((Scrollable)view).getPreferredScrollableViewportSize();
	}
	else {
	    return view.getPreferredSize();
	}
public voidremoveLayoutComponent(java.awt.Component c)
Removes the specified component from the layout. Not used by this class.

param
c the component to remove