Java tutorial
/* * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.swing; import java.awt.*; import java.beans.ConstructorProperties; import java.io.Serializable; /** * A layout manager to arrange components over the top * of each other. The requested size of the container * will be the largest requested size of the children, * taking alignment needs into consideration. * * The alignment is based upon what is needed to properly * fit the children in the allocation area. The children * will be placed such that their alignment points are all * on top of each other. * <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 Timothy Prinzing * @since 1.2 */ @SuppressWarnings("serial") // Same-version serialization only public class OverlayLayout implements LayoutManager2, Serializable { /** * Constructs a layout manager that performs overlay * arrangement of the children. The layout manager * created is dedicated to the given container. * * @param target the container to do layout against */ @ConstructorProperties({ "target" }) public OverlayLayout(Container target) { this.target = target; } /** * 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; } /** * Indicates a child has changed its layout related information, * which causes any cached calculations to be flushed. * * @param target the container */ public void invalidateLayout(Container target) { checkContainer(target); xChildren = null; yChildren = null; xTotal = null; yTotal = null; } /** * Adds the specified component to the layout. Used by * this class to know when to invalidate layout. * * @param name the name of the component * @param comp the component to be added */ public void addLayoutComponent(String name, Component comp) { invalidateLayout(comp.getParent()); } /** * Removes the specified component from the layout. Used by * this class to know when to invalidate layout. * * @param comp the component to remove */ public void removeLayoutComponent(Component comp) { invalidateLayout(comp.getParent()); } /** * Adds the specified component to the layout, using the specified * constraint object. Used by this class to know when to invalidate * layout. * * @param comp the component to be added * @param constraints where/how the component is added to the layout. */ 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. Recomputes the layout if it * has been invalidated. Factors in the current inset setting returned * by getInsets(). * * @param target the component which needs to be laid out * @return a Dimension object containing the preferred dimensions * @see #minimumLayoutSize */ public Dimension preferredLayoutSize(Container target) { checkContainer(target); checkRequests(); Dimension size = new Dimension(xTotal.preferred, yTotal.preferred); Insets insets = target.getInsets(); size.width += insets.left + insets.right; size.height += insets.top + insets.bottom; return size; } /** * Returns the minimum dimensions needed to lay out the components * contained in the specified target container. Recomputes the layout * if it has been invalidated, and factors in the current inset setting. * * @param target the component which needs to be laid out * @return a Dimension object containing the minimum dimensions * @see #preferredLayoutSize */ public Dimension minimumLayoutSize(Container target) { checkContainer(target); checkRequests(); Dimension size = new Dimension(xTotal.minimum, yTotal.minimum); Insets insets = target.getInsets(); size.width += insets.left + insets.right; size.height += insets.top + insets.bottom; return size; } /** * Returns the maximum dimensions needed to lay out the components * contained in the specified target container. Recomputes the * layout if it has been invalidated, and factors in the inset setting * returned by <code>getInset</code>. * * @param target the component that needs to be laid out * @return a <code>Dimension</code> object containing the maximum * dimensions * @see #preferredLayoutSize */ public Dimension maximumLayoutSize(Container target) { checkContainer(target); checkRequests(); Dimension size = new Dimension(xTotal.maximum, yTotal.maximum); Insets insets = target.getInsets(); size.width += insets.left + insets.right; size.height += insets.top + insets.bottom; return size; } /** * Returns the alignment along the x axis for the container. * * @param target the container * @return the alignment >= 0.0f && <= 1.0f */ public float getLayoutAlignmentX(Container target) { checkContainer(target); checkRequests(); return xTotal.alignment; } /** * Returns the alignment along the y axis for the container. * * @param target the container * @return the alignment >= 0.0f && <= 1.0f */ public float getLayoutAlignmentY(Container target) { checkContainer(target); checkRequests(); return yTotal.alignment; } /** * 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 * constructor */ public void layoutContainer(Container target) { checkContainer(target); checkRequests(); int nChildren = target.getComponentCount(); int[] xOffsets = new int[nChildren]; int[] xSpans = new int[nChildren]; int[] yOffsets = new int[nChildren]; int[] ySpans = new int[nChildren]; // determine the child placements Dimension alloc = target.getSize(); Insets in = target.getInsets(); alloc.width -= in.left + in.right; alloc.height -= in.top + in.bottom; SizeRequirements.calculateAlignedPositions(alloc.width, xTotal, xChildren, xOffsets, xSpans); SizeRequirements.calculateAlignedPositions(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(in.left + xOffsets[i], in.top + yOffsets[i], xSpans[i], ySpans[i]); } } void checkContainer(Container target) { if (this.target != target) { throw new AWTError("OverlayLayout 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); 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()); } xTotal = SizeRequirements.getAlignedSizeRequirements(xChildren); yTotal = SizeRequirements.getAlignedSizeRequirements(yChildren); } } private Container target; private SizeRequirements[] xChildren; private SizeRequirements[] yChildren; private SizeRequirements xTotal; private SizeRequirements yTotal; }