columnlayout.java

java 的164个例子的源代码,包括了 很多方面,供包括了19个方面的 源代码

/*
 * 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; }
}