swing使用布局实现伸缩面板

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/vcshcn/article/details/50703959

首先定义一个垂直布局类

public class VerticalLayout implements LayoutManager {

	private final int space;

	public VerticalLayout() {
		this(0);
	}

	public VerticalLayout(int space) {
		this.space = space;
	}

	@Override
	public Dimension minimumLayoutSize(Container parent) {
		Dimension r = new Dimension(0,0);
		for (Component c : parent.getComponents()) {
			Dimension d = c.getMinimumSize();
			r.width = Math.max(r.width, d.width);
			r.height += d.height;
		}
		return r;
	}

	@Override
	public void layoutContainer(Container parent) {
		int y = 0;
		for (Component c : parent.getComponents()) {
			if (c.isVisible()) {
				if (c instanceof ItemLabel && y > 0) {
					y += space;
				}
				Dimension d = c.getPreferredSize();
				c.setBounds(0, y, parent.getWidth(), d.height);
				y += d.height;
			}
		}
	}

然后定义一个面板类：

public class ExpandPanel  extends JComponent 

		setLayout(new VerticalLayout(space));

使用此垂直布局，增加一些方法：

	public void addItem(ExpandItem item) {
		items.add(item);
		add(item.getTitle());
		add(item.getPanel());
	}

	public void select(int index) {
		if (index <items.size()) {
			for (int i=0; i<items.size(); i++) {
				ExpandItem item = items.get(index);
				item.setVisible(index == i);
			}
		}
	}

ExpandItem为一个带标签的面板，结构如下：

public class ExpandItem {

	private ItemLabel title;
	private final JPanel pnlItems ;

	class ItemLabel extends JLabel {...}

效果如下：