https://openjdk.java.net/ 
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 * 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,
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 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package java.awt;

import java.util.Hashtable;
import java.util.Vector;
import java.util.Enumeration;

import java.io.Serializable;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectStreamField;
import java.io.IOException;


A CardLayout object is a layout manager for a container. It treats each component in the container as a card. Only one card is visible at a time, and the container acts as a stack of cards. The first component added to a CardLayout object is the visible component when the container is first displayed. 
 The ordering of cards is determined by the container's own internal ordering of its component objects. CardLayout defines a set of methods that allow an application to flip through these cards sequentially, or to show a specified card. The addLayoutComponent method can be used to associate a string identifier with a given card for fast random access. 
Author:     Arthur van Hoff
See Also:
Since:      1.0
/**
 * A {@code CardLayout} object is a layout manager for a
 * container. It treats each component in the container as a card.
 * Only one card is visible at a time, and the container acts as
 * a stack of cards. The first component added to a
 * {@code CardLayout} object is the visible component when the
 * container is first displayed.
 * <p>
 * The ordering of cards is determined by the container's own internal
 * ordering of its component objects. {@code CardLayout}
 * defines a set of methods that allow an application to flip
 * through these cards sequentially, or to show a specified card.
 * The {@link CardLayout#addLayoutComponent}
 * method can be used to associate a string identifier with a given card
 * for fast random access.
 *
 * @author      Arthur van Hoff
 * @see         java.awt.Container
 * @since       1.0
 */

public class CardLayout implements LayoutManager2,
                                   Serializable {

    private static final long serialVersionUID = -4328196481005934313L;

    /*
     * This creates a Vector to store associated
     * pairs of components and their names.
     * @see java.util.Vector
     */
    Vector<Card> vector = new Vector<>();

    /*
     * A pair of Component and String that represents its name.
     */
    class Card implements Serializable {
        static final long serialVersionUID = 6640330810709497518L;
        public String name;
        public Component comp;
        public Card(String cardName, Component cardComponent) {
            name = cardName;
            comp = cardComponent;
        }
    }

    /*
     * Index of Component currently displayed by CardLayout.
     */
    int currentCard = 0;


    /*
    * A cards horizontal Layout gap (inset). It specifies
    * the space between the left and right edges of a
    * container and the current component.
    * This should be a non negative Integer.
    * @see getHgap()
    * @see setHgap()
    */
    int hgap;

    /*
    * A cards vertical Layout gap (inset). It specifies
    * the space between the top and bottom edges of a
    * container and the current component.
    * This should be a non negative Integer.
    * @see getVgap()
    * @see setVgap()
    */
    int vgap;

    
@serialFieldtab         Hashtable
     deprecated, for forward compatibility only
@serialFieldhgap        int
@serialFieldvgap        int
@serialFieldvector      Vector
@serialFieldcurrentCard int
/**
     * @serialField tab         Hashtable
     *      deprecated, for forward compatibility only
     * @serialField hgap        int
     * @serialField vgap        int
     * @serialField vector      Vector
     * @serialField currentCard int
     */
    private static final ObjectStreamField[] serialPersistentFields = {
        new ObjectStreamField("tab", Hashtable.class),
        new ObjectStreamField("hgap", Integer.TYPE),
        new ObjectStreamField("vgap", Integer.TYPE),
        new ObjectStreamField("vector", Vector.class),
        new ObjectStreamField("currentCard", Integer.TYPE)
    };

    
Creates a new card layout with gaps of size zero.

/**
     * Creates a new card layout with gaps of size zero.
     */
    public CardLayout() {
        this(0, 0);
    }

    
Creates a new card layout with the specified horizontal and
vertical gaps. The horizontal gaps are placed at the left and
right edges. The vertical gaps are placed at the top and bottom
edges.

Params:
  • hgap –   the horizontal gap.
  • vgap –   the vertical gap.
/**
     * Creates a new card layout with the specified horizontal and
     * vertical gaps. The horizontal gaps are placed at the left and
     * right edges. The vertical gaps are placed at the top and bottom
     * edges.
     * @param     hgap   the horizontal gap.
     * @param     vgap   the vertical gap.
     */
    public CardLayout(int hgap, int vgap) {
        this.hgap = hgap;
        this.vgap = vgap;
    }

    
Gets the horizontal gap between components.

See Also:
Returns:   the horizontal gap between components.
Since:    1.1
/**
     * Gets the horizontal gap between components.
     * @return    the horizontal gap between components.
     * @see       java.awt.CardLayout#setHgap(int)
     * @see       java.awt.CardLayout#getVgap()
     * @since     1.1
     */
    public int getHgap() {
        return hgap;
    }

    
Sets the horizontal gap between components.

Params:
  • hgap – the horizontal gap between components.
See Also:
Since:    1.1
/**
     * Sets the horizontal gap between components.
     * @param hgap the horizontal gap between components.
     * @see       java.awt.CardLayout#getHgap()
     * @see       java.awt.CardLayout#setVgap(int)
     * @since     1.1
     */
    public void setHgap(int hgap) {
        this.hgap = hgap;
    }

    
Gets the vertical gap between components.

See Also:
Returns:the vertical gap between components.
/**
     * Gets the vertical gap between components.
     * @return the vertical gap between components.
     * @see       java.awt.CardLayout#setVgap(int)
     * @see       java.awt.CardLayout#getHgap()
     */
    public int getVgap() {
        return vgap;
    }

    
Sets the vertical gap between components.

Params:
  • vgap – the vertical gap between components.
See Also:
Since:    1.1
/**
     * Sets the vertical gap between components.
     * @param     vgap the vertical gap between components.
     * @see       java.awt.CardLayout#getVgap()
     * @see       java.awt.CardLayout#setHgap(int)
     * @since     1.1
     */
    public void setVgap(int vgap) {
        this.vgap = vgap;
    }

    
Adds the specified component to this card layout's internal table of names. The object specified by constraints must be a string. The card layout stores this string as a key-value pair that can be used for random access to a particular card. By calling the show method, an application can display the component with the specified name. 
Params:
  • comp –          the component to be added.
  • constraints –   a tag that identifies a particular
                                       card in the layout.
Throws:
See Also:
/**
     * Adds the specified component to this card layout's internal
     * table of names. The object specified by {@code constraints}
     * must be a string. The card layout stores this string as a key-value
     * pair that can be used for random access to a particular card.
     * By calling the {@code show} method, an application can
     * display the component with the specified name.
     * @param     comp          the component to be added.
     * @param     constraints   a tag that identifies a particular
     *                                        card in the layout.
     * @see       java.awt.CardLayout#show(java.awt.Container, java.lang.String)
     * @exception  IllegalArgumentException  if the constraint is not a string.
     */
    public void addLayoutComponent(Component comp, Object constraints) {
      synchronized (comp.getTreeLock()) {
          if (constraints == null){
              constraints = "";
          }
        if (constraints instanceof String) {
            addLayoutComponent((String)constraints, comp);
        } else {
            throw new IllegalArgumentException("cannot add to layout: constraint must be a string");
        }
      }
    }

    
Deprecated: replaced by addLayoutComponent(Component, Object).
/**
     * @deprecated   replaced by
     *      {@code addLayoutComponent(Component, Object)}.
     */
    @Deprecated
    public void addLayoutComponent(String name, Component comp) {
        synchronized (comp.getTreeLock()) {
            if (!vector.isEmpty()) {
                comp.setVisible(false);
            }
            for (int i=0; i < vector.size(); i++) {
                if ((vector.get(i)).name.equals(name)) {
                    (vector.get(i)).comp = comp;
                    return;
                }
            }
            vector.add(new Card(name, comp));
        }
    }

    
Removes the specified component from the layout.
If the card was visible on top, the next card underneath it is shown.

Params:
  • comp –   the component to be removed.
See Also:
/**
     * Removes the specified component from the layout.
     * If the card was visible on top, the next card underneath it is shown.
     * @param   comp   the component to be removed.
     * @see     java.awt.Container#remove(java.awt.Component)
     * @see     java.awt.Container#removeAll()
     */
    public void removeLayoutComponent(Component comp) {
        synchronized (comp.getTreeLock()) {
            for (int i = 0; i < vector.size(); i++) {
                if ((vector.get(i)).comp == comp) {
                    // if we remove current component we should show next one
                    if (comp.isVisible() && (comp.getParent() != null)) {
                        next(comp.getParent());
                    }

                    vector.remove(i);

                    // correct currentCard if this is necessary
                    if (currentCard > i) {
                        currentCard--;
                    }
                    break;
                }
            }
        }
    }

    
Determines the preferred size of the container argument using
this card layout.

Params:
  • parent – the parent container in which to do the layout
See Also:
Returns: the preferred dimensions to lay out the subcomponents
               of the specified container
/**
     * Determines the preferred size of the container argument using
     * this card layout.
     * @param   parent the parent container in which to do the layout
     * @return  the preferred dimensions to lay out the subcomponents
     *                of the specified container
     * @see     java.awt.Container#getPreferredSize
     * @see     java.awt.CardLayout#minimumLayoutSize
     */
    public Dimension preferredLayoutSize(Container parent) {
        synchronized (parent.getTreeLock()) {
            Insets insets = parent.getInsets();
            int ncomponents = parent.getComponentCount();
            int w = 0;
            int h = 0;

            for (int i = 0 ; i < ncomponents ; i++) {
                Component comp = parent.getComponent(i);
                Dimension d = comp.getPreferredSize();
                if (d.width > w) {
                    w = d.width;
                }
                if (d.height > h) {
                    h = d.height;
                }
            }
            return new Dimension(insets.left + insets.right + w + hgap*2,
                                 insets.top + insets.bottom + h + vgap*2);
        }
    }

    
Calculates the minimum size for the specified panel.

Params:
  • parent – the parent container in which to do the layout
See Also:
Returns:   the minimum dimensions required to lay out the
               subcomponents of the specified container
/**
     * Calculates the minimum size for the specified panel.
     * @param     parent the parent container in which to do the layout
     * @return    the minimum dimensions required to lay out the
     *                subcomponents of the specified container
     * @see       java.awt.Container#doLayout
     * @see       java.awt.CardLayout#preferredLayoutSize
     */
    public Dimension minimumLayoutSize(Container parent) {
        synchronized (parent.getTreeLock()) {
            Insets insets = parent.getInsets();
            int ncomponents = parent.getComponentCount();
            int w = 0;
            int h = 0;

            for (int i = 0 ; i < ncomponents ; i++) {
                Component comp = parent.getComponent(i);
                Dimension d = comp.getMinimumSize();
                if (d.width > w) {
                    w = d.width;
                }
                if (d.height > h) {
                    h = d.height;
                }
            }
            return new Dimension(insets.left + insets.right + w + hgap*2,
                                 insets.top + insets.bottom + h + vgap*2);
        }
    }

    
Returns the maximum dimensions for this layout given the components
in the specified target container.

Params:
  • target – the component which needs to be laid out
See Also:
/**
     * Returns the maximum dimensions for this layout given the components
     * in the specified target container.
     * @param target the component which needs to be laid out
     * @see Container
     * @see #minimumLayoutSize
     * @see #preferredLayoutSize
     */
    public Dimension maximumLayoutSize(Container target) {
        return new Dimension(Integer.MAX_VALUE, Integer.MAX_VALUE);
    }

    
Returns the alignment along the x axis.  This specifies how
the component would like to be aligned relative to other
components.  The value should be a number between 0 and 1
where 0 represents alignment along the origin, 1 is aligned
the furthest away from the origin, 0.5 is centered, etc.

/**
     * Returns the alignment along the x axis.  This specifies how
     * the component would like to be aligned relative to other
     * components.  The value should be a number between 0 and 1
     * where 0 represents alignment along the origin, 1 is aligned
     * the furthest away from the origin, 0.5 is centered, etc.
     */
    public float getLayoutAlignmentX(Container parent) {
        return 0.5f;
    }

    
Returns the alignment along the y axis.  This specifies how
the component would like to be aligned relative to other
components.  The value should be a number between 0 and 1
where 0 represents alignment along the origin, 1 is aligned
the furthest away from the origin, 0.5 is centered, etc.

/**
     * Returns the alignment along the y axis.  This specifies how
     * the component would like to be aligned relative to other
     * components.  The value should be a number between 0 and 1
     * where 0 represents alignment along the origin, 1 is aligned
     * the furthest away from the origin, 0.5 is centered, etc.
     */
    public float getLayoutAlignmentY(Container parent) {
        return 0.5f;
    }

    
Invalidates the layout, indicating that if the layout manager
has cached information it should be discarded.

/**
     * Invalidates the layout, indicating that if the layout manager
     * has cached information it should be discarded.
     */
    public void invalidateLayout(Container target) {
    }

    
Lays out the specified container using this card layout.

 Each component in the parent container is reshaped to be the size of the container, minus space for surrounding insets, horizontal gaps, and vertical gaps. 
Params:
  • parent – the parent container in which to do the layout
See Also:
/**
     * Lays out the specified container using this card layout.
     * <p>
     * Each component in the {@code parent} container is reshaped
     * to be the size of the container, minus space for surrounding
     * insets, horizontal gaps, and vertical gaps.
     *
     * @param     parent the parent container in which to do the layout
     * @see       java.awt.Container#doLayout
     */
    public void layoutContainer(Container parent) {
        synchronized (parent.getTreeLock()) {
            Insets insets = parent.getInsets();
            int ncomponents = parent.getComponentCount();
            Component comp = null;
            boolean currentFound = false;

            for (int i = 0 ; i < ncomponents ; i++) {
                comp = parent.getComponent(i);
                comp.setBounds(hgap + insets.left, vgap + insets.top,
                               parent.width - (hgap*2 + insets.left + insets.right),
                               parent.height - (vgap*2 + insets.top + insets.bottom));
                if (comp.isVisible()) {
                    currentFound = true;
                }
            }

            if (!currentFound && ncomponents > 0) {
                parent.getComponent(0).setVisible(true);
            }
        }
    }

    
Make sure that the Container really has a CardLayout installed.
Otherwise havoc can ensue!

/**
     * Make sure that the Container really has a CardLayout installed.
     * Otherwise havoc can ensue!
     */
    void checkLayout(Container parent) {
        if (parent.getLayout() != this) {
            throw new IllegalArgumentException("wrong parent for CardLayout");
        }
    }

    
Flips to the first card of the container.

Params:
  • parent –   the parent container in which to do the layout
See Also:
/**
     * Flips to the first card of the container.
     * @param     parent   the parent container in which to do the layout
     * @see       java.awt.CardLayout#last
     */
    public void first(Container parent) {
        synchronized (parent.getTreeLock()) {
            checkLayout(parent);
            int ncomponents = parent.getComponentCount();
            for (int i = 0 ; i < ncomponents ; i++) {
                Component comp = parent.getComponent(i);
                if (comp.isVisible()) {
                    comp.setVisible(false);
                    break;
                }
            }
            if (ncomponents > 0) {
                currentCard = 0;
                parent.getComponent(0).setVisible(true);
                parent.validate();
            }
        }
    }

    
Flips to the next card of the specified container. If the
currently visible card is the last one, this method flips to the
first card in the layout.

Params:
  • parent –   the parent container in which to do the layout
See Also:
/**
     * Flips to the next card of the specified container. If the
     * currently visible card is the last one, this method flips to the
     * first card in the layout.
     * @param     parent   the parent container in which to do the layout
     * @see       java.awt.CardLayout#previous
     */
    public void next(Container parent) {
        synchronized (parent.getTreeLock()) {
            checkLayout(parent);
            int ncomponents = parent.getComponentCount();
            for (int i = 0 ; i < ncomponents ; i++) {
                Component comp = parent.getComponent(i);
                if (comp.isVisible()) {
                    comp.setVisible(false);
                    currentCard = (i + 1) % ncomponents;
                    comp = parent.getComponent(currentCard);
                    comp.setVisible(true);
                    parent.validate();
                    return;
                }
            }
            showDefaultComponent(parent);
        }
    }

    
Flips to the previous card of the specified container. If the
currently visible card is the first one, this method flips to the
last card in the layout.

Params:
  • parent –   the parent container in which to do the layout
See Also:
/**
     * Flips to the previous card of the specified container. If the
     * currently visible card is the first one, this method flips to the
     * last card in the layout.
     * @param     parent   the parent container in which to do the layout
     * @see       java.awt.CardLayout#next
     */
    public void previous(Container parent) {
        synchronized (parent.getTreeLock()) {
            checkLayout(parent);
            int ncomponents = parent.getComponentCount();
            for (int i = 0 ; i < ncomponents ; i++) {
                Component comp = parent.getComponent(i);
                if (comp.isVisible()) {
                    comp.setVisible(false);
                    currentCard = ((i > 0) ? i-1 : ncomponents-1);
                    comp = parent.getComponent(currentCard);
                    comp.setVisible(true);
                    parent.validate();
                    return;
                }
            }
            showDefaultComponent(parent);
        }
    }

    void showDefaultComponent(Container parent) {
        if (parent.getComponentCount() > 0) {
            currentCard = 0;
            parent.getComponent(0).setVisible(true);
            parent.validate();
        }
    }

    
Flips to the last card of the container.

Params:
  • parent –   the parent container in which to do the layout
See Also:
/**
     * Flips to the last card of the container.
     * @param     parent   the parent container in which to do the layout
     * @see       java.awt.CardLayout#first
     */
    public void last(Container parent) {
        synchronized (parent.getTreeLock()) {
            checkLayout(parent);
            int ncomponents = parent.getComponentCount();
            for (int i = 0 ; i < ncomponents ; i++) {
                Component comp = parent.getComponent(i);
                if (comp.isVisible()) {
                    comp.setVisible(false);
                    break;
                }
            }
            if (ncomponents > 0) {
                currentCard = ncomponents - 1;
                parent.getComponent(currentCard).setVisible(true);
                parent.validate();
            }
        }
    }

    
Flips to the component that was added to this layout with the specified name, using addLayoutComponent. If no such component exists, then nothing happens. 
Params:
  • parent –   the parent container in which to do the layout
  • name –     the component name
See Also:
/**
     * Flips to the component that was added to this layout with the
     * specified {@code name}, using {@code addLayoutComponent}.
     * If no such component exists, then nothing happens.
     * @param     parent   the parent container in which to do the layout
     * @param     name     the component name
     * @see       java.awt.CardLayout#addLayoutComponent(java.awt.Component, java.lang.Object)
     */
    public void show(Container parent, String name) {
        synchronized (parent.getTreeLock()) {
            checkLayout(parent);
            Component next = null;
            int ncomponents = vector.size();
            for (int i = 0; i < ncomponents; i++) {
                Card card = vector.get(i);
                if (card.name.equals(name)) {
                    next = card.comp;
                    currentCard = i;
                    break;
                }
            }
            if ((next != null) && !next.isVisible()) {
                ncomponents = parent.getComponentCount();
                for (int i = 0; i < ncomponents; i++) {
                    Component comp = parent.getComponent(i);
                    if (comp.isVisible()) {
                        comp.setVisible(false);
                        break;
                    }
                }
                next.setVisible(true);
                parent.validate();
            }
        }
    }

    
Returns a string representation of the state of this card layout.

Returns:   a string representation of this card layout.
/**
     * Returns a string representation of the state of this card layout.
     * @return    a string representation of this card layout.
     */
    public String toString() {
        return getClass().getName() + "[hgap=" + hgap + ",vgap=" + vgap + "]";
    }

    
Reads serializable fields from stream.

/**
     * Reads serializable fields from stream.
     */
    @SuppressWarnings("unchecked")
    private void readObject(ObjectInputStream s)
        throws ClassNotFoundException, IOException
    {
        ObjectInputStream.GetField f = s.readFields();

        hgap = f.get("hgap", 0);
        vgap = f.get("vgap", 0);

        if (f.defaulted("vector")) {
            //  pre-1.4 stream
            Hashtable<String, Component> tab = (Hashtable)f.get("tab", null);
            vector = new Vector<>();
            if (tab != null && !tab.isEmpty()) {
                for (Enumeration<String> e = tab.keys() ; e.hasMoreElements() ; ) {
                    String key = e.nextElement();
                    Component comp = tab.get(key);
                    vector.add(new Card(key, comp));
                    if (comp.isVisible()) {
                        currentCard = vector.size() - 1;
                    }
                }
            }
        } else {
            vector = (Vector)f.get("vector", null);
            currentCard = f.get("currentCard", 0);
        }
    }

    
Writes serializable fields to stream.

/**
     * Writes serializable fields to stream.
     */
    private void writeObject(ObjectOutputStream s)
        throws IOException
    {
        Hashtable<String, Component> tab = new Hashtable<>();
        int ncomponents = vector.size();
        for (int i = 0; i < ncomponents; i++) {
            Card card = vector.get(i);
            tab.put(card.name, card.comp);
        }

        ObjectOutputStream.PutField f = s.putFields();
        f.put("hgap", hgap);
        f.put("vgap", vgap);
        f.put("vector", vector);
        f.put("currentCard", currentCard);
        f.put("tab", tab);
        s.writeFields();
    }
}