PositionalLayout.java

/*
 * Copyright (c) 2014 tabletoptool.com team.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Public License v3.0
 * which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/gpl.html
 * 
 * Contributors:
 *     rptools.com team - initial implementation
 *     tabletoptool.com team - further development
 */
package com.t3.swing;

import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.LayoutManager2;
import java.util.HashMap;
import java.util.Map;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;


/**
 */
public class PositionalLayout implements LayoutManager2 {

    public enum Position {
        
        NW, N, NE,
        W, CENTER, E,
        SW, S, SE
    }

    private int padding = 0; 

    private Map<Component, Position> compPositionMap = new HashMap<Component, Position>();

    public PositionalLayout() {}
    
    public PositionalLayout(int edgePadding) {
        padding = edgePadding;
    }
    
    @Override
	public void addLayoutComponent(Component comp,Object constraints){
        if (! (constraints instanceof Position)) {
            return;
        }
        
        compPositionMap.put(comp, (Position) constraints);
    }
    
    @Override
	public void addLayoutComponent(String name, Component comp) {
        throw new IllegalArgumentException("Use add(comp, Position)");
    }
    
    @Override
	public float getLayoutAlignmentX(Container target){
        return 0;
    }
    
    @Override
	public float getLayoutAlignmentY(Container target){
        return 0;
    }
    
    @Override
	public void invalidateLayout(Container target) {
        // Nothing to do right now
    }
    
    @Override
	public void layoutContainer(Container parent) {
        
        Dimension size = parent.getSize();
        
        Component[] compArray = parent.getComponents();
        for (Component comp : compArray) {
            
            Position pos = compPositionMap.get(comp);
            Dimension compSize = comp.getSize();
            
            int x = 0;
            int y = 0;
            
            switch(pos) {
            case NW: {x = padding; y = padding; break;}
            case N:  {x = center(size.width, compSize.width); y = padding; break;}
            case NE: {x = size.width - compSize.width - padding; y = padding; break;}
            case W:  {x = padding; y = center(size.height, compSize.height); break;}
            case E:  {x = size.width - compSize.width - padding; y = center(size.height, compSize.height); break;}
            case SW: {x = padding; y = size.height - compSize.height - padding; break;}
            case S:  {x = center(size.width, compSize.width); y = size.height - compSize.height - padding; break;}
            case SE: {x = size.width - compSize.width - padding; y = size.height - compSize.height - padding; break;}
            case CENTER: {
                x = 0;
                y = 0;
                
                // Fill available space
                comp.setSize(size);
            }
            }
            
            comp.setLocation(x, y);
        }
    }
    
    private int center (int outsideWidth, int insideWidth) {
        return (outsideWidth - insideWidth) / 2;
    }
    
    @Override
	public Dimension maximumLayoutSize(Container target){
        return preferredLayoutSize(target);
    }
    
    @Override
	public Dimension minimumLayoutSize(Container parent) {
        return preferredLayoutSize(parent);
    }
    
    @Override
	public Dimension preferredLayoutSize(Container parent) {
        return new Dimension(0,0);
    }
    
    @Override
	public void removeLayoutComponent(Component comp) {

        compPositionMap.remove(comp);
    }

    public static void main (String[] args) {
        
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new PositionalPanel();
        
        panel.add(createButton("NW"), Position.NW);
        panel.add(createButton("N"), Position.N);
        panel.add(createButton("NE"), Position.NE);
        panel.add(createButton("W"), Position.W);
        panel.add(createButton("E"), Position.E);
        panel.add(createButton("SW"), Position.SW);
        panel.add(createButton("S"), Position.S);
        panel.add(createButton("SE"), Position.SE);
        panel.add(createButton("CENTER"), Position.CENTER);
        
        frame.setContentPane(panel);
        
        frame.setSize(200, 200);
        frame.setVisible(true);
    }
    
    private static JButton createButton(String label) {
        JButton button = new JButton (label);
        button.setSize(button.getMinimumSize());
        
        return button;
    }
}