Java tutorial
/* * Copyright (c) 1997, 2017, 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.Component; import java.util.ArrayList; import java.util.Hashtable; import java.awt.Color; import java.awt.Graphics; import java.awt.Rectangle; import java.beans.JavaBean; import java.beans.BeanProperty; import sun.awt.SunToolkit; import javax.accessibility.*; /** * <code>JLayeredPane</code> adds depth to a JFC/Swing container, * allowing components to overlap each other when needed. * An <code>Integer</code> object specifies each component's depth in the * container, where higher-numbered components sit "on top" of other * components. * For task-oriented documentation and examples of using layered panes see * <a href="https://docs.oracle.com/javase/tutorial/uiswing/components/layeredpane.html">How to Use a Layered Pane</a>, * a section in <em>The Java Tutorial</em>. * * <table class="borderless" style="float:right"> * <caption>Example</caption> * <TR> * <TD style="text-align:center"> * <P STYLE="TEXT-ALIGN:CENTER"><IMG SRC="doc-files/JLayeredPane-1.gif" * alt="The following text describes this image." * WIDTH="269" HEIGHT="264" STYLE="FLOAT:BOTTOM; BORDER=0"> * </TD> * </TR> * </TABLE> * For convenience, <code>JLayeredPane</code> divides the depth-range * into several different layers. Putting a component into one of those * layers makes it easy to ensure that components overlap properly, * without having to worry about specifying numbers for specific depths: * <DL> * <DT>DEFAULT_LAYER</DT> * <DD>The standard layer, where most components go. This the bottommost * layer. * <DT>PALETTE_LAYER</DT> * <DD>The palette layer sits over the default layer. Useful for floating * toolbars and palettes, so they can be positioned above other components. * <DT>MODAL_LAYER</DT> * <DD>The layer used for modal dialogs. They will appear on top of any * toolbars, palettes, or standard components in the container. * <DT>POPUP_LAYER</DT> * <DD>The popup layer displays above dialogs. That way, the popup windows * associated with combo boxes, tooltips, and other help text will appear * above the component, palette, or dialog that generated them. * <DT>DRAG_LAYER</DT> * <DD>When dragging a component, reassigning it to the drag layer ensures * that it is positioned over every other component in the container. When * finished dragging, it can be reassigned to its normal layer. * </DL> * The <code>JLayeredPane</code> methods <code>moveToFront(Component)</code>, * <code>moveToBack(Component)</code> and <code>setPosition</code> can be used * to reposition a component within its layer. The <code>setLayer</code> method * can also be used to change the component's current layer. * * <h2>Details</h2> * <code>JLayeredPane</code> manages its list of children like * <code>Container</code>, but allows for the definition of a several * layers within itself. Children in the same layer are managed exactly * like the normal <code>Container</code> object, * with the added feature that when children components overlap, children * in higher layers display above the children in lower layers. * <p> * Each layer is a distinct integer number. The layer attribute can be set * on a <code>Component</code> by passing an <code>Integer</code> * object during the add call.<br> For example: * <PRE> * layeredPane.add(child, JLayeredPane.DEFAULT_LAYER); * or * layeredPane.add(child, Integer.valueOf.valueOf(10)); * </PRE> * The layer attribute can also be set on a Component by calling<PRE> * layeredPaneParent.setLayer(child, 10)</PRE> * on the <code>JLayeredPane</code> that is the parent of component. The layer * should be set <i>before</i> adding the child to the parent. * <p> * Higher number layers display above lower number layers. So, using * numbers for the layers and letters for individual components, a * representative list order would look like this:<PRE> * 5a, 5b, 5c, 2a, 2b, 2c, 1a </PRE> * where the leftmost components are closest to the top of the display. * <p> * A component can be moved to the top or bottom position within its * layer by calling <code>moveToFront</code> or <code>moveToBack</code>. * <p> * The position of a component within a layer can also be specified directly. * Valid positions range from 0 up to one less than the number of * components in that layer. A value of -1 indicates the bottommost * position. A value of 0 indicates the topmost position. Unlike layer * numbers, higher position values are <i>lower</i> in the display. * <blockquote> * <b>Note:</b> This sequence (defined by java.awt.Container) is the reverse * of the layer numbering sequence. Usually though, you will use <code>moveToFront</code>, * <code>moveToBack</code>, and <code>setLayer</code>. * </blockquote> * Here are some examples using the method add(Component, layer, position): * Calling add(5x, 5, -1) results in:<PRE> * 5a, 5b, 5c, 5x, 2a, 2b, 2c, 1a </PRE> * * Calling add(5z, 5, 2) results in:<PRE> * 5a, 5b, 5z, 5c, 5x, 2a, 2b, 2c, 1a </PRE> * * Calling add(3a, 3, 7) results in:<PRE> * 5a, 5b, 5z, 5c, 5x, 3a, 2a, 2b, 2c, 1a </PRE> * * Using normal paint/event mechanics results in 1a appearing at the bottom * and 5a being above all other components. * <p> * <b>Note:</b> that these layers are simply a logical construct and LayoutManagers * will affect all child components of this container without regard for * layer settings. * <p> * <strong>Warning:</strong> Swing is not thread safe. For more * information see <a * href="package-summary.html#threading">Swing's Threading * Policy</a>. * <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 David Kloba * @since 1.2 */ @JavaBean(defaultProperty = "accessibleContext") @SuppressWarnings("serial") public class JLayeredPane extends JComponent implements Accessible { /// Watch the values in getObjectForLayer() /** Convenience object defining the Default layer. Equivalent to Integer.valueOf(0).*/ public static final Integer DEFAULT_LAYER = 0; /** Convenience object defining the Palette layer. Equivalent to Integer.valueOf(100).*/ public static final Integer PALETTE_LAYER = 100; /** Convenience object defining the Modal layer. Equivalent to Integer.valueOf(200).*/ public static final Integer MODAL_LAYER = 200; /** Convenience object defining the Popup layer. Equivalent to Integer.valueOf(300).*/ public static final Integer POPUP_LAYER = 300; /** Convenience object defining the Drag layer. Equivalent to Integer.valueOf(400).*/ public static final Integer DRAG_LAYER = 400; /** Convenience object defining the Frame Content layer. * This layer is normally only use to position the contentPane and menuBar * components of JFrame. * Equivalent to Integer.valueOf(-30000). * @see JFrame */ public static final Integer FRAME_CONTENT_LAYER = -30000; /** Bound property */ public static final String LAYER_PROPERTY = "layeredContainerLayer"; // Hashtable to store layer values for non-JComponent components private Hashtable<Component, Integer> componentToLayer; private boolean optimizedDrawingPossible = true; ////////////////////////////////////////////////////////////////////////////// //// Container Override methods ////////////////////////////////////////////////////////////////////////////// /** Create a new JLayeredPane */ public JLayeredPane() { setLayout(null); } private void validateOptimizedDrawing() { boolean layeredComponentFound = false; synchronized (getTreeLock()) { Integer layer; for (Component c : getComponents()) { layer = null; if (SunToolkit.isInstanceOf(c, "javax.swing.JInternalFrame") || (c instanceof JComponent && (layer = (Integer) ((JComponent) c).getClientProperty(LAYER_PROPERTY)) != null)) { if (layer != null && layer.equals(FRAME_CONTENT_LAYER)) continue; layeredComponentFound = true; break; } } } if (layeredComponentFound) optimizedDrawingPossible = false; else optimizedDrawingPossible = true; } protected void addImpl(Component comp, Object constraints, int index) { int layer; int pos; if (constraints instanceof Integer) { layer = ((Integer) constraints).intValue(); setLayer(comp, layer); } else layer = getLayer(comp); pos = insertIndexForLayer(layer, index); super.addImpl(comp, constraints, pos); comp.validate(); comp.repaint(); validateOptimizedDrawing(); } /** * Remove the indexed component from this pane. * This is the absolute index, ignoring layers. * * @param index an int specifying the component to remove * @see #getIndexOf */ public void remove(int index) { Component c = getComponent(index); super.remove(index); if (c != null && !(c instanceof JComponent)) { getComponentToLayer().remove(c); } validateOptimizedDrawing(); } /** * Removes all the components from this container. * * @since 1.5 */ public void removeAll() { Component[] children = getComponents(); Hashtable<Component, Integer> cToL = getComponentToLayer(); for (int counter = children.length - 1; counter >= 0; counter--) { Component c = children[counter]; if (c != null && !(c instanceof JComponent)) { cToL.remove(c); } } super.removeAll(); } /** * Returns false if components in the pane can overlap, which makes * optimized drawing impossible. Otherwise, returns true. * * @return false if components can overlap, else true * @see JComponent#isOptimizedDrawingEnabled */ @BeanProperty(bound = false) public boolean isOptimizedDrawingEnabled() { return optimizedDrawingPossible; } ////////////////////////////////////////////////////////////////////////////// //// New methods for managing layers ////////////////////////////////////////////////////////////////////////////// /** Sets the layer property on a JComponent. This method does not cause * any side effects like setLayer() (painting, add/remove, etc). * Normally you should use the instance method setLayer(), in order to * get the desired side-effects (like repainting). * * @param c the JComponent to move * @param layer an int specifying the layer to move it to * @see #setLayer */ public static void putLayer(JComponent c, int layer) { /// MAKE SURE THIS AND setLayer(Component c, int layer, int position) are SYNCED c.putClientProperty(LAYER_PROPERTY, layer); } /** Gets the layer property for a JComponent, it * does not cause any side effects like setLayer(). (painting, add/remove, etc) * Normally you should use the instance method getLayer(). * * @param c the JComponent to check * @return an int specifying the component's layer */ public static int getLayer(JComponent c) { Integer i; if ((i = (Integer) c.getClientProperty(LAYER_PROPERTY)) != null) return i.intValue(); return DEFAULT_LAYER.intValue(); } /** Convenience method that returns the first JLayeredPane which * contains the specified component. Note that all JFrames have a * JLayeredPane at their root, so any component in a JFrame will * have a JLayeredPane parent. * * @param c the Component to check * @return the JLayeredPane that contains the component, or * null if no JLayeredPane is found in the component * hierarchy * @see JFrame * @see JRootPane */ public static JLayeredPane getLayeredPaneAbove(Component c) { if (c == null) return null; Component parent = c.getParent(); while (parent != null && !(parent instanceof JLayeredPane)) parent = parent.getParent(); return (JLayeredPane) parent; } /** Sets the layer attribute on the specified component, * making it the bottommost component in that layer. * Should be called before adding to parent. * * @param c the Component to set the layer for * @param layer an int specifying the layer to set, where * lower numbers are closer to the bottom */ public void setLayer(Component c, int layer) { setLayer(c, layer, -1); } /** Sets the layer attribute for the specified component and * also sets its position within that layer. * * @param c the Component to set the layer for * @param layer an int specifying the layer to set, where * lower numbers are closer to the bottom * @param position an int specifying the position within the * layer, where 0 is the topmost position and -1 * is the bottommost position */ public void setLayer(Component c, int layer, int position) { Integer layerObj; layerObj = getObjectForLayer(layer); if (layer == getLayer(c) && position == getPosition(c)) { repaint(c.getBounds()); return; } /// MAKE SURE THIS AND putLayer(JComponent c, int layer) are SYNCED if (c instanceof JComponent) ((JComponent) c).putClientProperty(LAYER_PROPERTY, layerObj); else getComponentToLayer().put(c, layerObj); if (c.getParent() == null || c.getParent() != this) { repaint(c.getBounds()); return; } int index = insertIndexForLayer(c, layer, position); setComponentZOrder(c, index); repaint(c.getBounds()); } /** * Returns the layer attribute for the specified Component. * * @param c the Component to check * @return an int specifying the component's current layer */ public int getLayer(Component c) { Integer i; if (c instanceof JComponent) i = (Integer) ((JComponent) c).getClientProperty(LAYER_PROPERTY); else i = getComponentToLayer().get(c); if (i == null) return DEFAULT_LAYER.intValue(); return i.intValue(); } /** * Returns the index of the specified Component. * This is the absolute index, ignoring layers. * Index numbers, like position numbers, have the topmost component * at index zero. Larger numbers are closer to the bottom. * * @param c the Component to check * @return an int specifying the component's index */ public int getIndexOf(Component c) { int i, count; count = getComponentCount(); for (i = 0; i < count; i++) { if (c == getComponent(i)) return i; } return -1; } /** * Moves the component to the top of the components in its current layer * (position 0). * * @param c the Component to move * @see #setPosition(Component, int) */ public void moveToFront(Component c) { setPosition(c, 0); } /** * Moves the component to the bottom of the components in its current layer * (position -1). * * @param c the Component to move * @see #setPosition(Component, int) */ public void moveToBack(Component c) { setPosition(c, -1); } /** * Moves the component to <code>position</code> within its current layer, * where 0 is the topmost position within the layer and -1 is the bottommost * position. * <p> * <b>Note:</b> Position numbering is defined by java.awt.Container, and * is the opposite of layer numbering. Lower position numbers are closer * to the top (0 is topmost), and higher position numbers are closer to * the bottom. * * @param c the Component to move * @param position an int in the range -1..N-1, where N is the number of * components in the component's current layer */ public void setPosition(Component c, int position) { setLayer(c, getLayer(c), position); } /** * Get the relative position of the component within its layer. * * @param c the Component to check * @return an int giving the component's position, where 0 is the * topmost position and the highest index value = the count * count of components at that layer, minus 1 * * @see #getComponentCountInLayer */ public int getPosition(Component c) { int i, startLayer, curLayer, startLocation, pos = 0; getComponentCount(); startLocation = getIndexOf(c); if (startLocation == -1) return -1; startLayer = getLayer(c); for (i = startLocation - 1; i >= 0; i--) { curLayer = getLayer(getComponent(i)); if (curLayer == startLayer) pos++; else return pos; } return pos; } /** Returns the highest layer value from all current children. * Returns 0 if there are no children. * * @return an int indicating the layer of the topmost component in the * pane, or zero if there are no children */ public int highestLayer() { if (getComponentCount() > 0) return getLayer(getComponent(0)); return 0; } /** Returns the lowest layer value from all current children. * Returns 0 if there are no children. * * @return an int indicating the layer of the bottommost component in the * pane, or zero if there are no children */ public int lowestLayer() { int count = getComponentCount(); if (count > 0) return getLayer(getComponent(count - 1)); return 0; } /** * Returns the number of children currently in the specified layer. * * @param layer an int specifying the layer to check * @return an int specifying the number of components in that layer */ public int getComponentCountInLayer(int layer) { int i, count, curLayer; int layerCount = 0; count = getComponentCount(); for (i = 0; i < count; i++) { curLayer = getLayer(getComponent(i)); if (curLayer == layer) { layerCount++; /// Short circut the counting when we have them all } else if (layerCount > 0 || curLayer < layer) { break; } } return layerCount; } /** * Returns an array of the components in the specified layer. * * @param layer an int specifying the layer to check * @return an array of Components contained in that layer */ public Component[] getComponentsInLayer(int layer) { int i, count, curLayer; int layerCount = 0; Component[] results; results = new Component[getComponentCountInLayer(layer)]; count = getComponentCount(); for (i = 0; i < count; i++) { curLayer = getLayer(getComponent(i)); if (curLayer == layer) { results[layerCount++] = getComponent(i); /// Short circut the counting when we have them all } else if (layerCount > 0 || curLayer < layer) { break; } } return results; } /** * Paints this JLayeredPane within the specified graphics context. * * @param g the Graphics context within which to paint */ public void paint(Graphics g) { if (isOpaque()) { Rectangle r = g.getClipBounds(); Color c = getBackground(); if (c == null) c = Color.lightGray; g.setColor(c); if (r != null) { g.fillRect(r.x, r.y, r.width, r.height); } else { g.fillRect(0, 0, getWidth(), getHeight()); } } super.paint(g); } ////////////////////////////////////////////////////////////////////////////// //// Implementation Details ////////////////////////////////////////////////////////////////////////////// /** * Returns the hashtable that maps components to layers. * * @return the Hashtable used to map components to their layers */ protected Hashtable<Component, Integer> getComponentToLayer() { if (componentToLayer == null) componentToLayer = new Hashtable<Component, Integer>(4); return componentToLayer; } /** * Returns the Integer object associated with a specified layer. * * @param layer an int specifying the layer * @return an Integer object for that layer */ protected Integer getObjectForLayer(int layer) { switch (layer) { case 0: return DEFAULT_LAYER; case 100: return PALETTE_LAYER; case 200: return MODAL_LAYER; case 300: return POPUP_LAYER; case 400: return DRAG_LAYER; default: return layer; } } /** * Primitive method that determines the proper location to * insert a new child based on layer and position requests. * * @param layer an int specifying the layer * @param position an int specifying the position within the layer * @return an int giving the (absolute) insertion-index * * @see #getIndexOf */ protected int insertIndexForLayer(int layer, int position) { return insertIndexForLayer(null, layer, position); } /** * This method is an extended version of insertIndexForLayer() * to support setLayer which uses Container.setZOrder which does * not remove the component from the containment hierarchy though * we need to ignore it when calculating the insertion index. * * @param comp component to ignore when determining index * @param layer an int specifying the layer * @param position an int specifying the position within the layer * @return an int giving the (absolute) insertion-index * * @see #getIndexOf */ private int insertIndexForLayer(Component comp, int layer, int position) { int i, count, curLayer; int layerStart = -1; int layerEnd = -1; int componentCount = getComponentCount(); ArrayList<Component> compList = new ArrayList<Component>(componentCount); for (int index = 0; index < componentCount; index++) { if (getComponent(index) != comp) { compList.add(getComponent(index)); } } count = compList.size(); for (i = 0; i < count; i++) { curLayer = getLayer(compList.get(i)); if (layerStart == -1 && curLayer == layer) { layerStart = i; } if (curLayer < layer) { if (i == 0) { // layer is greater than any current layer // [ ASSERT(layer > highestLayer()) ] layerStart = 0; layerEnd = 0; } else { layerEnd = i; } break; } } // layer requested is lower than any current layer // [ ASSERT(layer < lowestLayer()) ] // put it on the bottom of the stack if (layerStart == -1 && layerEnd == -1) return count; // In the case of a single layer entry handle the degenerative cases if (layerStart != -1 && layerEnd == -1) layerEnd = count; if (layerEnd != -1 && layerStart == -1) layerStart = layerEnd; // If we are adding to the bottom, return the last element if (position == -1) return layerEnd; // Otherwise make sure the requested position falls in the // proper range if (position > -1 && layerStart + position <= layerEnd) return layerStart + position; // Otherwise return the end of the layer return layerEnd; } /** * Returns a string representation of this JLayeredPane. This method * is intended to be used only for debugging purposes, and the * content and format of the returned string may vary between * implementations. The returned string may be empty but may not * be <code>null</code>. * * @return a string representation of this JLayeredPane. */ protected String paramString() { String optimizedDrawingPossibleString = (optimizedDrawingPossible ? "true" : "false"); return super.paramString() + ",optimizedDrawingPossible=" + optimizedDrawingPossibleString; } ///////////////// // Accessibility support //////////////// /** * Gets the AccessibleContext associated with this JLayeredPane. * For layered panes, the AccessibleContext takes the form of an * AccessibleJLayeredPane. * A new AccessibleJLayeredPane instance is created if necessary. * * @return an AccessibleJLayeredPane that serves as the * AccessibleContext of this JLayeredPane */ @BeanProperty(bound = false) public AccessibleContext getAccessibleContext() { if (accessibleContext == null) { accessibleContext = new AccessibleJLayeredPane(); } return accessibleContext; } /** * This class implements accessibility support for the * <code>JLayeredPane</code> class. It provides an implementation of the * Java Accessibility API appropriate to layered pane user-interface * elements. * <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}. */ @SuppressWarnings("serial") protected class AccessibleJLayeredPane extends AccessibleJComponent { /** * Get the role of this object. * * @return an instance of AccessibleRole describing the role of the * object * @see AccessibleRole */ public AccessibleRole getAccessibleRole() { return AccessibleRole.LAYERED_PANE; } } }