/* * Copyright (c) 2000 David Flanagan.  All rights reserved. * This code is from the book Java Examples in a Nutshell, 2nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book (recommended), * visit http://www.davidflanagan.com/javaexamples2. */package com.davidflanagan.examples.gui;import java.awt.*;/** * This LayoutManager arranges the components into a column. * Components are always given their preferred size. * * When you create a ColumnLayout, you may specify four values: *   margin_height -- how much space to leave on top and bottom *   margin_width -- how much space to leave on left and right *   spacing -- how much vertical space to leave between items *   alignment -- the horizontal position of the components: *      ColumnLayout.LEFT -- left-justify the components *      ColumnLayout.CENTER -- horizontally center the components *      ColumnLayout.RIGHT -- right-justify the components * * You never call the methods of a ColumnLayout object.  Just create one * and make it the layout manager for your container by passing it to * the addLayout() method of the Container object. */public class ColumnLayout implements LayoutManager2 {    protected int margin_height;    protected int margin_width;    protected int spacing;    protected int alignment;        // Constants for the alignment argument to the constructor.    public static final int LEFT = 0;    public static final int CENTER = 1;    public static final int RIGHT = 2;        /** The constructor.  See comment above for meanings of these arguments */    public ColumnLayout(int margin_height, int margin_width,			int spacing, int alignment)  {	this.margin_height = margin_height;	this.margin_width = margin_width;	this.spacing = spacing;	this.alignment = alignment;    }        /**     * A default constructor that creates a ColumnLayout using 5-pixel     * margin width and height, 5-pixel spacing, and left alignment     **/    public ColumnLayout() { this(5, 5, 5, LEFT); }        /**     * The method that actually performs the layout.     * Called by the Container     **/    public void layoutContainer(Container parent) {	Insets insets = parent.getInsets();	Dimension parent_size = parent.getSize();	Component kid;	int nkids = parent.getComponentCount();	int x0 = insets.left + margin_width;  // The base X position	int x;	int y = insets.top + margin_height;   // Start at the top of the column		for(int i = 0; i < nkids; i++) {      // Loop through the kids	    kid = parent.getComponent(i);     // Get the kid	    if (!kid.isVisible()) continue;   // Skip hidden ones	    Dimension pref = kid.getPreferredSize();  // How big is it?	    switch(alignment) {               // Compute X coordinate	    default:	    case LEFT:   x = x0; break;	    case CENTER: x = (parent_size.width - pref.width)/2; break;	    case RIGHT:		x = parent_size.width-insets.right-margin_width-pref.width;		break;	    }	    // Set the size and position of this kid	    kid.setBounds(x, y, pref.width, pref.height);	    y += pref.height + spacing;       // Get Y position of the next one	}    }        /** The Container calls this to find out how big the layout should to be */    public Dimension preferredLayoutSize(Container parent) {	return layoutSize(parent, 1);    }    /** The Container calls this to find out how big the layout must be */    public Dimension minimumLayoutSize(Container parent) {	return layoutSize(parent, 2);    }    /** The Container calls this to find out how big the layout can be */    public Dimension maximumLayoutSize(Container parent) {	return layoutSize(parent, 3);    }    // Compute min, max, or preferred size of all the visible children    protected Dimension layoutSize(Container parent, int sizetype) {	int nkids = parent.getComponentCount();	Dimension size = new Dimension(0,0);	Insets insets = parent.getInsets();	int num_visible_kids = 0;		// Compute maximum width and total height of all visible kids	for(int i = 0; i < nkids; i++) {	    Component kid = parent.getComponent(i);	    Dimension d;	    if (!kid.isVisible()) continue;	    num_visible_kids++;	    if (sizetype == 1) d = kid.getPreferredSize();	    else if (sizetype == 2) d = kid.getMinimumSize();	    else d = kid.getMaximumSize();	    if (d.width > size.width) size.width = d.width;	    size.height += d.height;	}		// Now add in margins and stuff	size.width += insets.left + insets.right + 2*margin_width;	size.height += insets.top + insets.bottom + 2*margin_height;	if (num_visible_kids > 1)	    size.height += (num_visible_kids - 1) * spacing;	return size;    }        // Other LayoutManager(2) methods that are unused by this class    public void addLayoutComponent(String constraint, Component comp) {}    public void addLayoutComponent(Component comp, Object constraint) {}    public void removeLayoutComponent(Component comp) {}    public void invalidateLayout(Container parent) {}    public float getLayoutAlignmentX(Container parent) { return 0.5f; }    public float getLayoutAlignmentY(Container parent) { return 0.5f; }}