File	Doc	Category	Size	Date	Package
BoxLayout.java	API Doc	Java SE 6 API	19358	Tue Jun 10 00:26:34 BST 2008	javax.swing

BoxLayout

• java.lang.Object

Fields Summary
public static final int	X_AXIS Specifies that components should be laid out left to right.
public static final int	Y_AXIS Specifies that components should be laid out top to bottom.
public static final int	LINE_AXIS Specifies that components should be laid out in the direction of a line of text as determined by the target container's ComponentOrientation property.
public static final int	PAGE_AXIS Specifies that components should be laid out in the direction that lines flow across a page as determined by the target container's ComponentOrientation property.
private int	axis
private Container	target
private transient SizeRequirements[]	xChildren
private transient SizeRequirements[]	yChildren
private transient SizeRequirements	xTotal
private transient SizeRequirements	yTotal
private transient PrintStream	dbg

Constructors Summary
public BoxLayout(Container target, int axis) 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: BoxLayout.X_AXIS, BoxLayout.Y_AXIS, BoxLayout.LINE_AXIS or BoxLayout.PAGE_AXIS exception AWTError if the value of axis is invalid if (axis != X_AXIS && axis != Y_AXIS && axis != LINE_AXIS && axis != PAGE_AXIS) { throw new AWTError("Invalid axis"); } this.axis = axis; this.target = target;
BoxLayout(Container target, int axis, PrintStream dbg) 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: BoxLayout.X_AXIS, BoxLayout.Y_AXIS, BoxLayout.LINE_AXIS or BoxLayout.PAGE_AXIS param dbg the stream to which debugging messages should be sent, null if none this(target, axis); this.dbg = dbg;

Methods Summary
public void	addLayoutComponent(java.lang.String name, java.awt.Component comp) Not used by this class. param name the name of the component param comp the component invalidateLayout(comp.getParent());
public void	addLayoutComponent(java.awt.Component comp, java.lang.Object constraints) Not used by this class. param comp the component param constraints constraints invalidateLayout(comp.getParent());
void	checkContainer(java.awt.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(); xChildren[i] = new SizeRequirements(min.width, typ.width, max.width, c.getAlignmentX()); yChildren[i] = new SizeRequirements(min.height, typ.height, max.height, c.getAlignmentY()); } // Resolve axis to an absolute value (either X_AXIS or Y_AXIS) int absoluteAxis = resolveAxis(axis,target.getComponentOrientation()); if (absoluteAxis == X_AXIS) { xTotal = SizeRequirements.getTiledSizeRequirements(xChildren); yTotal = SizeRequirements.getAlignedSizeRequirements(yChildren); } else { xTotal = SizeRequirements.getAlignedSizeRequirements(xChildren); yTotal = SizeRequirements.getTiledSizeRequirements(yChildren); } }
public final int	getAxis() Returns the axis that was used to lay out components. Returns one of: BoxLayout.X_AXIS, BoxLayout.Y_AXIS, BoxLayout.LINE_AXIS or BoxLayout.PAGE_AXIS return the axis that was used to lay out components since 1.6 return this.axis;
public synchronized float	getLayoutAlignmentX(java.awt.Container target) 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 checkContainer(target); checkRequests(); return xTotal.alignment;
public synchronized float	getLayoutAlignmentY(java.awt.Container target) 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 checkContainer(target); checkRequests(); return yTotal.alignment;
public final java.awt.Container	getTarget() Returns the container that uses this layout manager. return the container that uses this layout manager since 1.6 return this.target;
public synchronized void	invalidateLayout(java.awt.Container target) Indicates that a child has changed its layout related information, and thus any cached calculations should be flushed. 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 checkContainer(target); xChildren = null; yChildren = null; xTotal = null; yTotal = null;
public void	layoutContainer(java.awt.Container target) Called by the AWT 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 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]); } }
public java.awt.Dimension	maximumLayoutSize(java.awt.Container target) 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 dimenions >= 0 && <= Integer.MAX_VALUE exception AWTError if the target isn't the container specified to the BoxLayout constructor see #preferredLayoutSize see #minimumLayoutSize 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;
public java.awt.Dimension	minimumLayoutSize(java.awt.Container target) 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 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;
public java.awt.Dimension	preferredLayoutSize(java.awt.Container target) 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 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;
public void	removeLayoutComponent(java.awt.Component comp) Not used by this class. param comp the component invalidateLayout(comp.getParent());
private int	resolveAxis(int axis, java.awt.ComponentOrientation o) Given one of the 4 axis values, resolve it to an absolute axis. The relative axis values, PAGE_AXIS and LINE_AXIS are converted to their absolute couterpart given the target's ComponentOrientation value. The absolute axes, X_AXIS and Y_AXIS are returned unmodified. param axis the axis to resolve param o the ComponentOrientation to resolve against return the resolved axis int absoluteAxis; if( axis == LINE_AXIS ) { absoluteAxis = o.isHorizontal() ? X_AXIS : Y_AXIS; } else if( axis == PAGE_AXIS ) { absoluteAxis = o.isHorizontal() ? Y_AXIS : X_AXIS; } else { absoluteAxis = axis; } return absoluteAxis;