Java Swing - 常识篇 之 LayoutManager 03
? ? 下面先来看一个例子：
package org.dui.sample;import java.awt.CardLayout;import java.awt.Dimension;import java.awt.Font;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.JButton;import javax.swing.JComponent;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JPanel;import javax.swing.SwingUtilities;import javax.swing.UIManager;import net.miginfocom.swing.MigLayout;/** * <code>CardLayoutSample</code> demonstrates how to use the * <code>CardLayout</code> * * @author Jimmy * @since <i> DUI v1.0.0 (Apr 1,2013)</i> */public class CardLayoutSample extends JPanel {private static final long serialVersionUID = 1L;/**Cache the index of the current displaying component*/private int m_iCurrent = 0;{try {UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());UIManager.put("Label.font", new Font("", Font.BOLD, 20));} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}/** * Just create an instance. * */public CardLayoutSample() {initGUI();}/** * Init the UI * * @since <i>DUI v.1.0.0 (Apr 1, 2013)</i> */public void initGUI() {this.setLayout(new MigLayout("ins 5", "grow,fill", "[grow,fill][fill]"));this.setPreferredSize(new Dimension(400,300));final CardLayout layoutCard = new CardLayout();final JPanel pnlCard = new JPanel(layoutCard);JButton btnPrev = new JButton("Prev");JButton btnNext = new JButton("Next");this.add(pnlCard, "cell 0 0").add(btnPrev, "cell 0 1, gapleft push").add(btnNext, "cell 0 1, gapright push");final String[] aNames = {"card1","card2", "card3", "card4"};pnlCard.add(new JLabel("Card1"), aNames[0]);pnlCard.add(new JLabel("Card2"), aNames[1]);pnlCard.add(new JLabel("Card3"), aNames[2]);pnlCard.add(new JLabel("Card4"), aNames[3]);btnPrev.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {m_iCurrent = m_iCurrent >= 1 ? --m_iCurrent : m_iCurrent;layoutCard.show(pnlCard, aNames[m_iCurrent]);}});btnNext.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {m_iCurrent = m_iCurrent < 3 ? ++m_iCurrent : m_iCurrent;layoutCard.show(pnlCard, aNames[m_iCurrent]);}});}/** * Add a Component specify by <code>oComp</code> to the container <code>self</code> * @param oComp * @param oConstraints * @return self * * @since <i>DUI v.1.0.0 (Apr 1, 2013)</i> */public CardLayoutSample add(JComponent oComp, Object oConstraints){super.add(oComp, oConstraints);return this;}public static void main(String[] args) {SwingUtilities.invokeLater(new Runnable() {@Overridepublic void run() {JFrame oFrame = new JFrame();oFrame.setTitle("CardLayoutSample");oFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);oFrame.setResizable(true);oFrame.setContentPane(new CardLayoutSample());oFrame.pack();oFrame.setVisible(true);oFrame.setLocationRelativeTo(null);}});}}? ? ? ? ? ?看了上面的例子，细心的你可能会发现，在程序中要用m_iCurrent来记录当前CarLayout所显示的组件，其实CardLayout有两个做得不够好的地方：
1）CardLayout没有提供方法去获取当前正在显示的组件。
2）当开始显示的整个Container的时候，CardLayout里面的组件没有得到聚焦。
为了解决上面两个问题，在这里提供一个增强版的CardLayout 命名为RCardLayout。例子在这里就不再写了，如果不会使用的朋友，可以留言。
package org.dui.sample;import java.awt.CardLayout;import java.awt.Component;import java.awt.Container;import java.awt.event.ActionEvent;import java.awt.event.HierarchyEvent;import java.awt.event.HierarchyListener;import java.util.ArrayList;import javax.swing.AbstractAction;import javax.swing.Action;import javax.swing.JComponent;/** * The <code>RCardLayout</code> provides some extensions to the CardLayout * class. In particular adding support for: * * a) setting focus on the card when it is displayed b) getting the currently * displayed Card c) Next and Previous Actions This added support will only work * when a JComponent is added as a Card. * * @since <i> DUI v1.0.0 (Apr 1,2013)</i> * */public class RCardLayout extends CardLayout implements HierarchyListener {private static final long serialVersionUID = 1L;private ArrayList<JComponent> cards = new ArrayList<JComponent>();private JComponent firstCard;private JComponent lastCard;private JComponent currentCard;private boolean isRequestFocusOnCard = true;private Action nextAction;private Action previousAction;/** * Creates a new card layout with gaps of size zero. */public RCardLayout() {this(0, 0);}/** * Creates a new card layout with the specified horizontal and vertical * gaps. The horizontal gaps are placed at the left and right edges. The * vertical gaps are placed at the top and bottom edges. * * @param hgap * the horizontal gap. * @param vgap * the vertical gap. */public RCardLayout(int hgap, int vgap) {super(hgap, vgap);}// Overridden methodspublic void addLayoutComponent(Component comp, Object constraints) {super.addLayoutComponent(comp, constraints);if (!(comp instanceof JComponent))return;JComponent component = (JComponent) comp;cards.add(component);if (firstCard == null)firstCard = component;lastCard = component;component.addHierarchyListener(this);}public void removeLayoutComponent(Component comp) {super.removeLayoutComponent(comp);if (!(comp instanceof JComponent))return;JComponent component = (JComponent) comp;component.removeHierarchyListener(this);cards.remove(component);if (component.equals(firstCard) && cards.size() > 0) {firstCard = cards.get(0);}if (component.equals(lastCard) && cards.size() > 0) {lastCard = cards.get(cards.size() - 1);}}// New methodspublic JComponent getCurrentCard() {return currentCard;}public Action getNextAction() {return getNextAction("Next");}public Action getNextAction(String name) {if (nextAction == null) {nextAction = new CardAction(name, true);nextAction.putValue(Action.MNEMONIC_KEY, (int) name.charAt(0));nextAction.setEnabled(isNextCardAvailable());}return nextAction;}public Action getPreviousAction() {return getPreviousAction("Previous");}public Action getPreviousAction(String name) {if (previousAction == null) {previousAction = new CardAction(name, false);previousAction.putValue(Action.MNEMONIC_KEY, (int) name.charAt(0));previousAction.setEnabled(isNextCardAvailable());}return previousAction;}public boolean isNextCardAvailable() {return currentCard != lastCard;}public boolean isPreviousCardAvailable() {return currentCard != firstCard;}public boolean isRequestFocusOnCard() {return isRequestFocusOnCard;}public void setRequestFocusOnCard(boolean isRequestFocusOnCard) {this.isRequestFocusOnCard = isRequestFocusOnCard;}// Implement Hierarchy Listener@Overridepublic void hierarchyChanged(HierarchyEvent e) {JComponent component = (JComponent) e.getSource();if ((HierarchyEvent.SHOWING_CHANGED & e.getChangeFlags()) != 0 && component.isShowing()) {currentCard = component;if (isRequestFocusOnCard)currentCard.transferFocus();if (nextAction != null)nextAction.setEnabled(isNextCardAvailable());if (previousAction != null)previousAction.setEnabled(isPreviousCardAvailable());}}class CardAction extends AbstractAction {private static final long serialVersionUID = 1L;private boolean isNext;public CardAction(String text, boolean isNext) {super(text);this.isNext = isNext;putValue(Action.SHORT_DESCRIPTION, getValue(Action.NAME));}public void actionPerformed(ActionEvent e) {Container parent = getCurrentCard().getParent();if (isNext)next(parent);elseprevious(parent);}}}?