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package javax.swing;
import java.awt.AWTError;
import java.awt.LayoutManager;
import java.awt.Component;
import java.awt.Container;
import java.awt.Rectangle;
import java.awt.Point;
import java.awt.Dimension;
import java.awt.Insets;
import java.io.Serializable;
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 JavaBeans™
has been added to the java.beans package. Please see XMLEncoder.
Author: Hans Muller Since: 1.2
/**
* The default layout manager for <code>JViewport</code>.
* <code>ViewportLayout</code> 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.
* <p>
* <strong>Warning:</strong>
* 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 <code>java.beans</code> package.
* Please see {@link java.beans.XMLEncoder}.
*
* @author Hans Muller
* @since 1.2
*/
@SuppressWarnings("serial") // Same-version serialization only
public class ViewportLayout implements LayoutManager, Serializable
{
// Single instance used by JViewport.
static ViewportLayout SHARED_INSTANCE = new ViewportLayout();
Adds the specified component to the layout. Not used by this class.
Params: - name – the name of the component
- c – the component to be added
/**
* Adds the specified component to the layout. Not used by this class.
* @param name the name of the component
* @param c the component to be added
*/
public void addLayoutComponent(String name, Component c) { }
Removes the specified component from the layout. Not used by
this class.
Params: - c – the component to remove
/**
* Removes the specified component from the layout. Not used by
* this class.
* @param c the component to remove
*/
public void removeLayoutComponent(Component c) { }
Returns the preferred dimensions for this layout given the components
in the specified target container.
Params: - parent – the component which needs to be laid out
See Also: Returns: a Dimension object containing the
preferred dimensions
/**
* 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 <code>Dimension</code> object containing the
* preferred dimensions
* @see #minimumLayoutSize
*/
public Dimension preferredLayoutSize(Container parent) {
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();
}
}
Returns the minimum dimensions needed to layout the components
contained in the specified target container.
Params: - parent – the component which needs to be laid out
See Also: Returns: a Dimension object containing the minimum
dimensions
/**
* 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 <code>Dimension</code> object containing the minimum
* dimensions
* @see #preferredLayoutSize
*/
public Dimension minimumLayoutSize(Container parent) {
return new Dimension(4, 4);
}
Called by the AWT when the specified container needs to be laid out.
Params: - parent – the container to lay out
Throws: - AWTError – if the target isn't the container specified to the
BoxLayout constructor
/**
* Called by the AWT when the specified container needs to be laid out.
*
* @param parent the container to lay out
*
* @throws AWTError if the target isn't the container specified to the
* <code>BoxLayout</code> constructor
*/
public void layoutContainer(Container parent)
{
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);
}
}