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* accompanied this code).
*
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package javax.swing;
import java.awt.*;
import java.beans.ConstructorProperties;
import java.io.Serializable;
import java.io.PrintStream;
/**
* A layout manager that allows multiple components to be laid out either
* vertically or horizontally. The components will not wrap so, for
* example, a vertical arrangement of components will stay vertically
* arranged when the frame is resized.
* <TABLE STYLE="FLOAT:RIGHT" BORDER="0" SUMMARY="layout">
* <TR>
* <TD ALIGN="CENTER">
* <P STYLE="TEXT-ALIGN:CENTER"><IMG SRC="doc-files/BoxLayout-1.gif"
* alt="The following text describes this graphic."
* WIDTH="191" HEIGHT="201" STYLE="FLOAT:BOTTOM; BORDER:0">
* </TD>
* </TR>
* </TABLE>
* <p>
* Nesting multiple panels with different combinations of horizontal and
* vertical gives an effect similar to GridBagLayout, without the
* complexity. The diagram shows two panels arranged horizontally, each
* of which contains 3 components arranged vertically.
*
* <p> The BoxLayout manager is constructed with an axis parameter that
* specifies the type of layout that will be done. There are four choices:
*
* <blockquote><b><tt>X_AXIS</tt></b> - Components are laid out horizontally
* from left to right.</blockquote>
*
* <blockquote><b><tt>Y_AXIS</tt></b> - Components are laid out vertically
* from top to bottom.</blockquote>
*
* <blockquote><b><tt>LINE_AXIS</tt></b> - Components are laid out the way
* words are laid out in a line, based on the container's
* <tt>ComponentOrientation</tt> property. If the container's
* <tt>ComponentOrientation</tt> is horizontal then components are laid out
* horizontally, otherwise they are laid out vertically. For horizontal
* orientations, if the container's <tt>ComponentOrientation</tt> is left to
* right then components are laid out left to right, otherwise they are laid
* out right to left. For vertical orientations components are always laid out
* from top to bottom.</blockquote>
*
* <blockquote><b><tt>PAGE_AXIS</tt></b> - Components are laid out the way
* text lines are laid out on a page, based on the container's
* <tt>ComponentOrientation</tt> property. If the container's
* <tt>ComponentOrientation</tt> is horizontal then components are laid out
* vertically, otherwise they are laid out horizontally. For horizontal
* orientations, if the container's <tt>ComponentOrientation</tt> is left to
* right then components are laid out left to right, otherwise they are laid
* out right to left. For vertical orientations components are always
* laid out from top to bottom.</blockquote>
* <p>
* For all directions, components are arranged in the same order as they were
* added to the container.
* <p>
* BoxLayout attempts to arrange components
* at their preferred widths (for horizontal layout)
* or heights (for vertical layout).
* For a horizontal layout,
* if not all the components are the same height,
* BoxLayout attempts to make all the components
* as high as the highest component.
* If that's not possible for a particular component,
* then BoxLayout aligns that component vertically,
* according to the component's Y alignment.
* By default, a component has a Y alignment of 0.5,
* which means that the vertical center of the component
* should have the same Y coordinate as
* the vertical centers of other components with 0.5 Y alignment.
* <p>
* Similarly, for a vertical layout,
* BoxLayout attempts to make all components in the column
* as wide as the widest component.
* If that fails, it aligns them horizontally
* according to their X alignments. For <code>PAGE_AXIS</code> layout,
* horizontal alignment is done based on the leading edge of the component.
* In other words, an X alignment value of 0.0 means the left edge of a
* component if the container's <code>ComponentOrientation</code> is left to
* right and it means the right edge of the component otherwise.
* <p>
* Instead of using BoxLayout directly, many programs use the Box class.
* The Box class is a lightweight container that uses a BoxLayout.
* It also provides handy methods to help you use BoxLayout well.
* Adding components to multiple nested boxes is a powerful way to get
* the arrangement you want.
* <p>
* For further information and examples see
* <a
href="https://docs.oracle.com/javase/tutorial/uiswing/layout/box.html">How to Use BoxLayout</a>,
* a section in <em>The Java Tutorial.</em>
* <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}.
*
* @see Box
* @see java.awt.ComponentOrientation
* @see JComponent#getAlignmentX
* @see JComponent#getAlignmentY
*
* @author Timothy Prinzing
*/
@SuppressWarnings("serial")
public class BoxLayout implements LayoutManager2, Serializable {
/**
* Specifies that components should be laid out left to right.
*/
public static final int X_AXIS = 0;
/**
* Specifies that components should be laid out top to bottom.
*/
public static final int Y_AXIS = 1;
/**
* Specifies that components should be laid out in the direction of
* a line of text as determined by the target container's
* <code>ComponentOrientation</code> property.
*/
public static final int LINE_AXIS = 2;
/**
* Specifies that components should be laid out in the direction that
* lines flow across a page as determined by the target container's
* <code>ComponentOrientation</code> property.
*/
public static final int PAGE_AXIS = 3;
/**
* Creates a layout manager that will lay out components along the
* given axis.
*
* @param target the container that needs to be laid out
* @param axis the axis to lay out components along. Can be one of:
* <code>BoxLayout.X_AXIS</code>,
* <code>BoxLayout.Y_AXIS</code>,
* <code>BoxLayout.LINE_AXIS</code> or
* <code>BoxLayout.PAGE_AXIS</code>
*
* @exception AWTError if the value of <code>axis</code> is invalid
*/
@ConstructorProperties({"target", "axis"})
public BoxLayout(Container target, int axis) {
if (axis != X_AXIS && axis != Y_AXIS &&
axis != LINE_AXIS && axis != PAGE_AXIS) {
throw new AWTError("Invalid axis");
}
this.axis = axis;
this.target = target;
}
/**
* Constructs a BoxLayout that
* produces debugging messages.
*
* @param target the container that needs to be laid out
* @param axis the axis to lay out components along. Can be one of:
* <code>BoxLayout.X_AXIS</code>,
* <code>BoxLayout.Y_AXIS</code>,
* <code>BoxLayout.LINE_AXIS</code> or
* <code>BoxLayout.PAGE_AXIS</code>
*
* @param dbg the stream to which debugging messages should be sent,
* null if none
*/
BoxLayout(Container target, int axis, PrintStream dbg) {
this(target, axis);
this.dbg = dbg;
}
/**
* Returns the container that uses this layout manager.
*
* @return the container that uses this layout manager
*
* @since 1.6
*/
public final Container getTarget() {
return this.target;
}
/**
* Returns the axis that was used to lay out components.
* Returns one of:
* <code>BoxLayout.X_AXIS</code>,
* <code>BoxLayout.Y_AXIS</code>,
* <code>BoxLayout.LINE_AXIS</code> or
* <code>BoxLayout.PAGE_AXIS</code>
*
* @return the axis that was used to lay out components
*
* @since 1.6
*/
public final int getAxis() {
return this.axis;
}
/**
* Indicates that a child has changed its layout related information,
* and thus any cached calculations should be flushed.
* <p>
* This method is called by AWT when the invalidate method is called
* on the Container. Since the invalidate method may be called
* asynchronously to the event thread, this method may be called
* asynchronously.
*
* @param target the affected container
*
* @exception AWTError if the target isn't the container specified to the
* BoxLayout constructor
*/
public synchronized void invalidateLayout(Container target) {
checkContainer(target);
xChildren = null;
yChildren = null;
xTotal = null;
yTotal = null;
}
/**
* Not used by this class.
*
* @param name the name of the component
* @param comp the component
*/
public void addLayoutComponent(String name, Component comp) {
invalidateLayout(comp.getParent());
}
/**
* Not used by this class.
*
* @param comp the component
*/
public void removeLayoutComponent(Component comp) {
invalidateLayout(comp.getParent());
}
/**
* Not used by this class.
*
* @param comp the component
* @param constraints constraints
*/
public void addLayoutComponent(Component comp, Object constraints) {
invalidateLayout(comp.getParent());
}
/**
* Returns the preferred dimensions for this layout, given the components
* in the specified target container.
*
* @param target the container that needs to be laid out
* @return the dimensions >= 0 && <= Integer.MAX_VALUE
* @exception AWTError if the target isn't the container specified to the
* BoxLayout constructor
* @see Container
* @see #minimumLayoutSize
* @see #maximumLayoutSize
*/
public Dimension preferredLayoutSize(Container target) {
Dimension size;
synchronized(this) {
checkContainer(target);
checkRequests();
size = new Dimension(xTotal.preferred, yTotal.preferred);
}
Insets insets = target.getInsets();
size.width = (int) Math.min((long) size.width + (long) insets.left + (long) insets.right, Integer.MAX_VALUE);
size.height = (int) Math.min((long) size.height + (long) insets.top + (long) insets.bottom, Integer.MAX_VALUE);
return size;
}
/**
* Returns the minimum dimensions needed to lay out the components
* contained in the specified target container.
*
* @param target the container that needs to be laid out
* @return the dimensions >= 0 && <= Integer.MAX_VALUE
* @exception AWTError if the target isn't the container specified to the
* BoxLayout constructor
* @see #preferredLayoutSize
* @see #maximumLayoutSize
*/
public Dimension minimumLayoutSize(Container target) {
Dimension size;
synchronized(this) {
checkContainer(target);
checkRequests();
size = new Dimension(xTotal.minimum, yTotal.minimum);
}
Insets insets = target.getInsets();
size.width = (int) Math.min((long) size.width + (long) insets.left + (long) insets.right, Integer.MAX_VALUE);
size.height = (int) Math.min((long) size.height + (long) insets.top + (long) insets.bottom, Integer.MAX_VALUE);
return size;
}
/**
* Returns the maximum dimensions the target container can use
* to lay out the components it contains.
*
* @param target the container that needs to be laid out
* @return the dimensions >= 0 && <= Integer.MAX_VALUE
* @exception AWTError if the target isn't the container specified to the
* BoxLayout constructor
* @see #preferredLayoutSize
* @see #minimumLayoutSize
*/
public Dimension maximumLayoutSize(Container target) {
Dimension size;
synchronized(this) {
checkContainer(target);
checkRequests();
size = new Dimension(xTotal.maximum, yTotal.maximum);
}
Insets insets = target.getInsets();
size.width = (int) Math.min((long) size.width + (long) insets.left + (long) insets.right, Integer.MAX_VALUE);
size.height = (int) Math.min((long) size.height + (long) insets.top + (long) insets.bottom, Integer.MAX_VALUE);
return size;
}
/**
* Returns the alignment along the X axis for the container.
* If the box is horizontal, the default
* alignment will be returned. Otherwise, the alignment needed
* to place the children along the X axis will be returned.
*
* @param target the container
* @return the alignment >= 0.0f && <= 1.0f
* @exception AWTError if the target isn't the container specified to the
* BoxLayout constructor
*/
public synchronized float getLayoutAlignmentX(Container target) {
checkContainer(target);
checkRequests();
return xTotal.alignment;
}
/**
* Returns the alignment along the Y axis for the container.
* If the box is vertical, the default
* alignment will be returned. Otherwise, the alignment needed
* to place the children along the Y axis will be returned.
*
* @param target the container
* @return the alignment >= 0.0f && <= 1.0f
* @exception AWTError if the target isn't the container specified to the
* BoxLayout constructor
*/
public synchronized float getLayoutAlignmentY(Container target) {
checkContainer(target);
checkRequests();
return yTotal.alignment;
}
/**
* Called by the AWT <!-- XXX CHECK! --> when the specified container
* needs to be laid out.
*
* @param target the container to lay out
*
* @exception AWTError if the target isn't the container specified to the
* BoxLayout constructor
*/
public void layoutContainer(Container target) {
checkContainer(target);
int nChildren = target.getComponentCount();
int[] xOffsets = new int[nChildren];
int[] xSpans = new int[nChildren];
int[] yOffsets = new int[nChildren];
int[] ySpans = new int[nChildren];
Dimension alloc = target.getSize();
Insets in = target.getInsets();
alloc.width -= in.left + in.right;
alloc.height -= in.top + in.bottom;
// Resolve axis to an absolute value (either X_AXIS or Y_AXIS)
ComponentOrientation o = target.getComponentOrientation();
int absoluteAxis = resolveAxis( axis, o );
boolean ltr = (absoluteAxis != axis) ? o.isLeftToRight() : true;
// determine the child placements
synchronized(this) {
checkRequests();
if (absoluteAxis == X_AXIS) {
SizeRequirements.calculateTiledPositions(alloc.width, xTotal,
xChildren, xOffsets,
xSpans, ltr);
SizeRequirements.calculateAlignedPositions(alloc.height, yTotal,
yChildren, yOffsets,
ySpans);
} else {
SizeRequirements.calculateAlignedPositions(alloc.width, xTotal,
xChildren, xOffsets,
xSpans, ltr);
SizeRequirements.calculateTiledPositions(alloc.height, yTotal,
yChildren, yOffsets,
ySpans);
}
}
// flush changes to the container
for (int i = 0; i < nChildren; i++) {
Component c = target.getComponent(i);
c.setBounds((int) Math.min((long) in.left + (long) xOffsets[i], Integer.MAX_VALUE),
(int) Math.min((long) in.top + (long) yOffsets[i], Integer.MAX_VALUE),
xSpans[i], ySpans[i]);
}
if (dbg != null) {
for (int i = 0; i < nChildren; i++) {
Component c = target.getComponent(i);
dbg.println(c.toString());
dbg.println("X: " + xChildren[i]);
dbg.println("Y: " + yChildren[i]);
}
}
}
void checkContainer(Container target) {
if (this.target != target) {
throw new AWTError("BoxLayout can't be shared");
}
}
void checkRequests() {
if (xChildren == null || yChildren == null) {
// The requests have been invalidated... recalculate
// the request information.
int n = target.getComponentCount();
xChildren = new SizeRequirements[n];
yChildren = new SizeRequirements[n];
for (int i = 0; i < n; i++) {
Component c = target.getComponent(i);
if (!c.isVisible()) {
xChildren[i] = new SizeRequirements(0,0,0, c.getAlignmentX());
yChildren[i] = new SizeRequirements(0,0,0, c.getAlignmentY());
continue;
}
Dimension min = c.getMinimumSize();
Dimension typ = c.getPreferredSize();
Dimension max = c.getMaximumSize();
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