java swing 垂直流布局管理器实现

最近写一个java UI，需要用到垂直流布局管理器，要求该管理器能够实现内部组件的宽度自适应。看了swing提供的5个布局管理器，尝试的实现效果都不理想，看来只能自己搞一个了，好在网上已有实现，其测试效果如下图：

图一 垂直流布局管理器实现效果

具体代码如下：

清单一：

import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Insets;

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

/**
 * VerticalFlowLayout is similar to FlowLayout except it lays out components
 * vertically. Extends FlowLayout because it mimics much of the behavior of the
 * FlowLayout class, except vertically. An additional feature is that you can
 * specify a fill to edge flag, which causes the VerticalFlowLayout manager to
 * resize all components to expand to the column width Warning: This causes
 * problems when the main panel has less space that it needs and it seems to
 * prohibit multi-column output. Additionally there is a vertical fill flag,
 * which fills the last component to the remaining height of the container.
 */
public class VFlowLayout extends FlowLayout
{
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	/**
	 * Specify alignment top.
	 */
	public static final int TOP = 0;

	/**
	 * Specify a middle alignment.
	 */
	public static final int MIDDLE = 1;

	/**
	 * Specify the alignment to be bottom.
	 */
	public static final int BOTTOM = 2;

	int hgap;
	int vgap;
	boolean hfill;
	boolean vfill;

	public static void main(String[] args)
	{
		System.out.println("Just for test ...");
		JFrame frame = new JFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setBounds(0, 0, 600, 600);
		frame.setLayout(new VFlowLayout());
		
		int i = 0;
		frame.add(new JButton(String.valueOf(i++)));
		frame.add(new JButton(String.valueOf(i++)));
		frame.add(new JButton(String.valueOf(i++)));
		frame.add(new JButton(String.valueOf(i++)));
		frame.add(new JButton(String.valueOf(i++)));
		frame.add(new JButton(String.valueOf(i++)));
		frame.add(new JButton(String.valueOf(i++)));
		frame.add(new JButton(String.valueOf(i++)));
		frame.add(new JButton(String.valueOf(i++)));
		frame.add(new JButton(String.valueOf(i++)));
		frame.add(new JButton(String.valueOf(i++)));
		
		frame.setVisible(true);
	}
	
	/**
	 * Construct a new VerticalFlowLayout with a middle alignment, and the fill
	 * to edge flag set.
	 */
	public VFlowLayout()
	{
		this(TOP, 5, 5, true, false);
	}

	/**
	 * Construct a new VerticalFlowLayout with a middle alignment.
	 * 
	 * @param hfill
	 *            the fill to edge flag
	 * @param vfill
	 *            the vertical fill in pixels.
	 */
	public VFlowLayout(boolean hfill, boolean vfill)
	{
		this(TOP, 5, 5, hfill, vfill);
	}

	/**
	 * Construct a new VerticalFlowLayout with a middle alignment.
	 * 
	 * @param align
	 *            the alignment value
	 */
	public VFlowLayout(int align)
	{
		this(align, 5, 5, true, false);
	}

	/**
	 * Construct a new VerticalFlowLayout.
	 * 
	 * @param align
	 *            the alignment value
	 * @param hfill
	 *            the horizontalfill in pixels.
	 * @param vfill
	 *            the vertical fill in pixels.
	 */
	public VFlowLayout(int align, boolean hfill, boolean vfill)
	{
		this(align, 5, 5, hfill, vfill);
	}

	/**
	 * Construct a new VerticalFlowLayout.
	 * 
	 * @param align
	 *            the alignment value
	 * @param hgap
	 *            the horizontal gap variable
	 * @param vgap
	 *            the vertical gap variable
	 * @param hfill
	 *            the fill to edge flag
	 * @param vfill
	 *            true if the panel should vertically fill.
	 */
	public VFlowLayout(int align, int hgap, int vgap, boolean hfill, boolean vfill)
	{
		setAlignment(align);
		this.hgap = hgap;
		this.vgap = vgap;
		this.hfill = hfill;
		this.vfill = vfill;
	}

	/**
	 * Returns the preferred dimensions given the components in the target
	 * container.
	 * 
	 * @param target
	 *            the component to lay out
	 */
	public Dimension preferredLayoutSize(Container target)
	{
		Dimension tarsiz = new Dimension(0, 0);

		for (int i = 0; i < target.getComponentCount(); i++)
		{
			Component m = target.getComponent(i);
			
			if (m.isVisible())
			{
				Dimension d = m.getPreferredSize();
				tarsiz.width = Math.max(tarsiz.width, d.width);
				
				if (i > 0)
				{
					tarsiz.height += hgap;
				}
				
				tarsiz.height += d.height;
			}
		}
		
		Insets insets = target.getInsets();
		tarsiz.width += insets.left + insets.right + hgap * 2;
		tarsiz.height += insets.top + insets.bottom + vgap * 2;
		
		return tarsiz;
	}

	/**
	 * Returns the minimum size needed to layout the target container.
	 * 
	 * @param target
	 *            the component to lay out.
	 * @return the minimum layout dimension.
	 */
	public Dimension minimumLayoutSize(Container target)
	{
		Dimension tarsiz = new Dimension(0, 0);

		for (int i = 0; i < target.getComponentCount(); i++)
		{
			Component m = target.getComponent(i);
			
			if (m.isVisible())
			{
				Dimension d = m.getMinimumSize();
				tarsiz.width = Math.max(tarsiz.width, d.width);
				
				if (i > 0) 
				{
					tarsiz.height += vgap;
				}
				
				tarsiz.height += d.height;
			}
		}
		
		Insets insets = target.getInsets();
		tarsiz.width += insets.left + insets.right + hgap * 2;
		tarsiz.height += insets.top + insets.bottom + vgap * 2;
		
		return tarsiz;
	}

	/**
	 * Set true to fill vertically.
	 * 
	 * @param vfill
	 *            true to fill vertically.
	 */
	public void setVerticalFill(boolean vfill)
	{
		this.vfill = vfill;
	}

	/**
	 * Returns true if the layout vertically fills.
	 * 
	 * @return true if vertically fills the layout using the specified.
	 */
	public boolean getVerticalFill()
	{
		return vfill;
	}

	/**
	 * Set to true to enable horizontally fill.
	 * 
	 * @param hfill
	 *            true to fill horizontally.
	 */
	public void setHorizontalFill(boolean hfill)
	{
		this.hfill = hfill;
	}

	/**
	 * Returns true if the layout horizontally fills.
	 * 
	 * @return true if horizontally fills.
	 */
	public boolean getHorizontalFill()
	{
		return hfill;
	}

	/**
	 * places the components defined by first to last within the target
	 * container using the bounds box defined.
	 * 
	 * @param target
	 *            the container.
	 * @param x
	 *            the x coordinate of the area.
	 * @param y
	 *            the y coordinate of the area.
	 * @param width
	 *            the width of the area.
	 * @param height
	 *            the height of the area.
	 * @param first
	 *            the first component of the container to place.
	 * @param last
	 *            the last component of the container to place.
	 */
	private void placethem(Container target, int x, int y, int width, int height, int first, int last)
	{
		int align = getAlignment();
		
		if (align == MIDDLE)
		{
			y += height / 2;
		}
		
		if (align == BOTTOM)
		{
			y += height;
		}
		
		for (int i = first; i < last; i++)
		{
			Component m = target.getComponent(i);
			Dimension md = m.getSize();
			
			if (m.isVisible())
			{
				int px = x + (width - md.width) / 2;
				m.setLocation(px, y);
				y += vgap + md.height;
			}
		}
	}

	/**
	 * Lays out the container.
	 * 
	 * @param target
	 *            the container to lay out.
	 */
	public void layoutContainer(Container target)
	{
		Insets insets = target.getInsets();
		int maxheight = target.getSize().height	- (insets.top + insets.bottom + vgap * 2);
		int maxwidth = target.getSize().width - (insets.left + insets.right + hgap * 2);
		int numcomp = target.getComponentCount();
		int x = insets.left + hgap, y = 0;
		int colw = 0, start = 0;

		for (int i = 0; i < numcomp; i++)
		{
			Component m = target.getComponent(i);
			
			if (m.isVisible()) 
			{
				Dimension d = m.getPreferredSize();
				
				// fit last component to remaining height
				if ((this.vfill) && (i == (numcomp - 1))) 
				{
					d.height = Math.max((maxheight - y), m.getPreferredSize().height);
				}

				// fit component size to container width
				if (this.hfill)
				{
					m.setSize(maxwidth, d.height);
					d.width = maxwidth;
				} 
				else
				{
					m.setSize(d.width, d.height);
				}

				if (y + d.height > maxheight)
				{
					placethem(target, x, insets.top + vgap, colw, maxheight - y, start, i);
					y = d.height;
					x += hgap + colw;
					colw = d.width;
					start = i;
				} 
				else
				{
					if (y > 0)
					{
						y += vgap;
					}
					
					y += d.height;
					colw = Math.max(colw, d.width);
				}
			}
		}
		
		placethem(target, x, insets.top + vgap, colw, maxheight - y, start,	numcomp);
	}
}