http://www.cnblogs.com/TLightSky/p/3482454.html

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原来的WrapLayout有点小bug，会引起抖动，稍微改了一下，现在比较好用了

package com.miui.theme.tool.gui;import java.awt.Component;import java.awt.Container;import java.awt.Dimension;import java.awt.FlowLayout;import java.awt.Insets;import javax.swing.JScrollPane;import javax.swing.SwingUtilities;/** * FlowLayout subclass that fully supports wrapping of components. */public class WrapLayout extends FlowLayout {    private Dimension preferredLayoutSize;    /**     * Constructs a new WrapLayout with a left alignment and a     * default 5-unit horizontal and vertical gap.     */    public WrapLayout() {        super();    }    /**     * Constructs a new FlowLayout with the specified alignment and     * a default 5-unit horizontal and vertical gap. The value of the alignment     * argument must be one of WrapLayout, WrapLayout,     * or WrapLayout.     *     * @param align     *            the alignment value     */    public WrapLayout(int align) {        super(align);    }    /**     * Creates a new flow layout manager with the indicated alignment and the     * indicated horizontal and vertical gaps.     * 
     * The value of the alignment argument must be one of     * WrapLayout, WrapLayout, or     * WrapLayout.     *     * @param align     *            the alignment value     * @param hgap     *            the horizontal gap between components     * @param vgap     *            the vertical gap between components     */    public WrapLayout(int align, int hgap, int vgap) {        super(align, hgap, vgap);    }    /**     * Returns the preferred dimensions for this layout given the visible     * components in the specified target container.     *     * @param target     *            the component which needs to be laid out     * @return the preferred dimensions to lay out the subcomponents of the     *         specified container     */    @Override    public Dimension preferredLayoutSize(Container target) {        return layoutSize(target, true);    }    /**     * Returns the minimum dimensions needed to layout the visible     * components contained in the specified target container.     *     * @param target     *            the component which needs to be laid out     * @return the minimum dimensions to lay out the subcomponents of the     *         specified container     */    @Override    public Dimension minimumLayoutSize(Container target) {        Dimension minimum = layoutSize(target, false);        minimum.width -= (getHgap() + 1);        return minimum;    }    /**     * Returns the minimum or preferred dimension needed to layout the target     * container.     *     * @param target     *            target to get layout size for     * @param preferred     *            should preferred size be calculated     * @return the dimension to layout the target container     */    private Dimension layoutSize(Container target, boolean preferred) {        synchronized (target.getTreeLock()) {            // Each row must fit with the width allocated to the containter.            // When the container width = 0, the preferred width of the            // container            // has not yet been calculated so lets ask for the maximum.            int targetWidth = target.getSize().width;            if (targetWidth == 0)                return new Dimension();//            if (targetWidth == 0)//                targetWidth = Integer.MAX_VALUE;            int hgap = getHgap();            int vgap = getVgap();            Insets insets = target.getInsets();            int horizontalInsetsAndGap = insets.left + insets.right + (hgap * 2);            int maxWidth = targetWidth - horizontalInsetsAndGap;            // Fit components into the allowed width            Dimension dim = new Dimension(0, 0);            int rowWidth = 0;            int rowHeight = 0;            int nmembers = target.getComponentCount();            for (int i = 0; i < nmembers; i++) {                Component m = target.getComponent(i);                if (m.isVisible()) {                    Dimension d = preferred ? m.getPreferredSize() : m.getMinimumSize();                    // Can't add the component to current row. Start a new row.                    if (rowWidth + d.width > maxWidth) {                        addRow(dim, rowWidth, rowHeight);                        rowWidth = 0;                        rowHeight = 0;                    }                    // Add a horizontal gap for all components after the first                    if (rowWidth != 0) {                        rowWidth += hgap;                    }                    rowWidth += d.width;                    rowHeight = Math.max(rowHeight, d.height);                }            }            addRow(dim, rowWidth, rowHeight);            dim.width += horizontalInsetsAndGap;            dim.height += insets.top + insets.bottom + vgap * 2;            // When using a scroll pane or the DecoratedLookAndFeel we need to            // make sure the preferred size is less than the size of the            // target containter so shrinking the container size works            // correctly. Removing the horizontal gap is an easy way to do this.            Container scrollPane = SwingUtilities.getAncestorOfClass(JScrollPane.class, target);            if (scrollPane != null && target.isValid()) {                dim.width -= (hgap + 1);            }            return dim;        }    }    /*     * A new row has been completed. Use the dimensions of this row to update     * the preferred size for the container.     *     * @param dim update the width and height when appropriate     *     * @param rowWidth the width of the row to add     *     * @param rowHeight the height of the row to add     */    private void addRow(Dimension dim, int rowWidth, int rowHeight) {        dim.width = Math.max(dim.width, rowWidth);        if (dim.height > 0) {            dim.height += getVgap();        }        dim.height += rowHeight;    }}