Java Swing实现垂直流布局

Java Swing实现垂直流布局

想实现一个仿QQ好友列表的界面，网上查了好久，发现基本都是用的GridLayout布局实现的，这个实现有一个bug，就是当好友数量较少的时候，组件会填满整个Frame，自己也尝试过其他的布局管理器，发现都不是那么好用。

后来发现有大佬写了一个垂直布局管理器，大佬文章链接：
https://blog.youkuaiyun.com/Dancen/article/details/7581971

大佬的这个垂直布局管理器存在一个bug，当Frame不能全部显示所有组件时，我们自然会想到用scrollPane，使用大佬的这个布局管理器会导致JScrollPane怎么都不会显示滚动条，即超出的组件将永远无法显示。故此，参考大佬的文章以及java.awt.FlowLayout类的写法。自己写了一个垂直布局管理器VerticalFlowLayout类。此类基本实现了FlowLayout的功能，同时增加了组件宽度自适应Frame的功能。现将源码发布如下，欢迎大家一起学习讨论。

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

/**
 * A vertical flow layout arranges components in a directional flow, much like
 * lines of text in a paragraph. VerticalFlow layouts are typically used to
 * arrange buttons in a panel. It arranges buttons vertically until no more
 * buttons fit on the same line. The line alignment is determined by the
 * <code>align</code> property. The possible values are:
 * <ul>
 * <li>{@link #TOP TOP}
 * <li>{@link #BOTTOM BOTTOM}
 * <li>{@link #CENTER CENTER}
 * </ul>
 * A vertical flow layout lets each component assume its natural (preferred)
 * size.
 */
public class VerticalFlowLayout implements LayoutManager {
   

	/**
	 * This value indicates that each row of components should be top-justified.
	 */
	public static final int TOP = 0;

	/**
	 * This value indicates that each row of components should be centered.
	 */
	public static final int CENTER = 1;

	/**
	 * This value indicates that each row of components should be
	 * bottom-justified.
	 */
	public static final int BOTTOM = 2;

	/**
	 * <code>align</code> is the property that determines how each column
	 * distributes empty space. It can be one of the following values:
	 * <ul>
	 * <li><code>TOP</code>
	 * <li><code>RIGHT</code>
	 * <li><code>BOTTOM</code>
	 * </ul>
	 *
	 * @see #getAlignment()
	 * @see #setAlignment(int)
	 */
	private int align;

	/**
	 * The vertical flow layout manager allows a separation of components with
	 * gaps. The horizontal gap will specify the space between columns and
	 * between the columns and the borders of the <code>Container</code>.
	 *
	 * 
	 * @see #getHgap()
	 * @see #setHgap(int)
	 */
	private int hgap;

	/**
	 * The vertical flow layout manager allows a separation of components with
	 * gaps. The vertical gap will specify the space between components and
	 * between the components and the borders of the <code>Container</code>.
	 *
	 * @see #getVgap()
	 * @see #setVgap(int)
	 */
	private int vgap;

	/**
	 * If true, components will be filled with <code>Container</code>
	 * horizontally.
	 * 
	 * @see #isHfill()
	 * @see #setHfill(boolean)
	 */
	private boolean hfill;

	/**
	 * Constructs a new <code>VerticalFlowLayout</code> with a centered
	 * alignment and a default 5-unit horizontal and vertical gaps and not
	 * filled with <code>Container</code> horizontally.
	 */
	public VerticalFlowLayout() {
   
		this(CENTER, 5, 5, false);
	}

	/**
	 * Constructs a new <code>FlowLayout</code> with the specified alignment and
	 * a default 5-unit horizontal and vertical gaps and not filled with
	 * <code>Container</code> horizontally. The value of the alignment argument
	 * must be one of <code>FlowLayout.TOP</code>,
	 * <code>FlowLayout.BOTTOM</code>, <code>FlowLayout.CENTER</code>.
	 * 
	 * @param align
	 *            the alignment value
	 */
	public VerticalFlowLayout(int align) {
   
		this(align, 5, 5, false);
	}

	/**
	 * Constructs a new <code>VerticalFlowLayout</code> with the indicated
	 * alignment and the indicated horizontal and vertical gaps and not filled
	 * with <code>Container</code> horizontally.
	 * <p>
	 * The value of the alignment argument must be one of
	 * <code>FlowLayout.TOP</code>, <code>FlowLayout.BOTTOM</code>,
	 * <code>FlowLayout.CENTER</code>.
	 * 
	 * @param align
	 *            the alignment value
	 * @param hgap
	 *            the horizontal gap between columns and between the columns and
	 *            the borders of the <code>Container</code>
	 * @param vgap
	 *            the vertical gap between components and between the components
	 *            and the borders of the <code>Container</code>
	 */
	public VerticalFlowLayout(int align, int hgap, int vgap) {
   
		this(align, hgap, vgap, false);
	}

	/**
	 * Constructs a new <code>VerticalFlowLayout</code> with the indicated
	 * alignment and the indicated horizontal and vertical gaps and the
	 * indicated filled with <code>Container</code> horizontally.