java-在cardlayout中切换卡片后运行方法

我敢肯定有人问过这个问题,但是今天我的google-fu并不强大.

我有一个使用CardLayout作为其管理器的JFrame.在不使用开关的情况下切换到每个JPanel时如何运行“启动”方法？

我用来将框架添加到布局的代码是：

/** * Adds JPanels to the Card Layout. * @param panel is the JPanel to add to the layout. * @param windowName is the identifier used to recognise the Panel. */ public final void addToCards(final JPanel panel, final WindowNames windowName) {     view.getBasePanel().add(panel, windowName.getValue()); }

我用来切换布局的代码是：

/** * Method to change the JPanel currently visible on the BasePanel. * @param windowName is the name of the JPanel to change to. */ public final void changePanel(final WindowNames windowName) {    view.getCardLayout().show(view.getBasePanel(), windowName.getValue()); }

当前,我有一个ActionListener集合,它将调用切换代码,但是我无法弄清楚如何在将要切换到的屏幕中调用“ Start”方法.

我为每个JPanels设置了接口,以便每个方法名称都相同.

解决方法:

您只能将ComponentListener用于面板.当面板成为CardLayout的视图时,它将触发组件事件并由侦听器中的componentShown处理(以及从视图中取出的面板,处理componentHidden).在此调用您的start()方法.这样,当面板更改时,您不必显式调用start(),因为它会为您调用.

有关更多详细信息,请参见How to Write Component Listeners.

这是一个简单的例子.

import java.awt.BorderLayout;import java.awt.CardLayout;import java.awt.Dimension;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.ComponentAdapter;import java.awt.event.ComponentEvent;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.SwingUtilities;public class Main {    private static final String PANEL_A = "panelA";    private static final String PANEL_B = "panelB";    CardLayout layout = new CardLayout();    JPanel panel = new JPanel(layout);    ComponentListenerPanel p1 = new ComponentListenerPanel(PANEL_A);    ComponentListenerPanel p2 = new ComponentListenerPanel(PANEL_B);    JButton b1 = new JButton(PANEL_A);    JButton b2 = new JButton(PANEL_B);    public Main() {        panel.add(p1, PANEL_A);        panel.add(p2, PANEL_B);        b1.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent e) {                show(PANEL_A);            }        });        b2.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent e) {                show(PANEL_B);            }        });        JPanel buttonPanel = new JPanel();        buttonPanel.add(b1);        buttonPanel.add(b2);        JFrame frame = new JFrame();        frame.add(panel);        frame.add(buttonPanel, BorderLayout.PAGE_END);        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        frame.pack();        frame.setLocationRelativeTo(null);        frame.setVisible(true);    }    public void show(String panelName) {        layout.show(panel, panelName);    }    private class ComponentListenerPanel extends JPanel {        private String panelName;        public ComponentListenerPanel(String panelName) {            this.panelName = panelName;            addComponentListener(new ComponentAdapter() {                @Override                public void componentHidden(ComponentEvent evt) {                    stop();                }                @Override                public void componentShown(ComponentEvent evt) {                    start();                }            });        }        public void start() {            System.out.println(panelName   " started");        }        public void stop() {            System.out.println(panelName   " stopped");        }        @Override        public Dimension getPreferredSize() {            return new Dimension(300, 300);        }    }    public static void main(String[] args) {        SwingUtilities.invokeLater(new Runnable() {            public void run() {                new Main();            }        });    }}

请注意,您实际上并未说过start方法在哪里,因此此代码/答案仅是假设您在自定义面板中有一些start方法.希望我猜对了.在将来,甚至现在,您都应该始终发布MCVE,这样我们就不必做所有这些猜测了.

来源：https://www.icode9.com/content-1-501601.html