Question

我在应用程序中使用cardlayout并想获取当前活动卡的名称我尝试了很多方法但没有意思，例如这种方法似乎不再存在

panel.getLayout().getActiveItem()

我也试过这个，但它也不起作用

 Panel card = null;
      for (Component comp : cardPanel.getComponents()) {
           if (comp.isVisible()) {
                System.out.println(card.getName());

                    }
                 }

例如：以下stamts在卡片布局中添加了几个面板，我想返回当前活动卡片的1,2,3,4或5个：

    cardPanel.add(firstP, "1");
    cardPanel.add(secondP, "2");
    cardPanel.add(thirdP, "3");
    cardPanel.add(fourthP, "4");
    cardPanel.add(fifthP, "5");

可能的方法是什么？

Answer 1

CardLayout不公开组件及其键之间的映射（此处为1，2，3，4 ...），所以使用布局本身不会揭示“卡片”是如何散列的。

如果您希望使用getName方法，请记住您必须先自己设置，因为默认情况下未设置字段：

firstPanel.setName("1");
cardPanel.add(firstPanel, firstPanel.getName());

然后，使用for循环，您将能够获得当前卡String。

Answer 2

有两种方式

determine visible JComponent from current card
putClientProperty（setName等）按AncestorListener或HierarchyListener

码

（免责声明，请注意，这只是Thread.sleep(int)的代码示例，仅适用于此形式，已设计锁定Event Dispatch Thread）

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.event.HierarchyEvent;
import java.awt.event.HierarchyListener;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.event.AncestorEvent;
import javax.swing.event.AncestorListener;

public class CardlayoutTest extends JFrame {

    private static final long serialVersionUID = 1L;
    private JPanel pnlA, pnlB, pnlC;
    public CardLayout card = new CardLayout();

    public CardlayoutTest() {
        EventHandler eventHandle = new EventHandler();
        pnlA = new JPanel(new BorderLayout());
        pnlA.add(new JButton("A"), BorderLayout.CENTER);
        pnlA.putClientProperty("JPanel", "JPanel_a");
        pnlB = new JPanel(new BorderLayout());
        pnlB.add(new JButton("B"), BorderLayout.CENTER);
        pnlB.putClientProperty("JPanel", "JPanel_b");
        pnlC = new JPanel(new BorderLayout());
        pnlC.add(new JButton("C"), BorderLayout.CENTER);
        pnlC.putClientProperty("JPanel", "JPanel_c");
        pnlA.addAncestorListener(eventHandle);
        pnlA.addHierarchyListener(eventHandle);
        pnlB.addAncestorListener(eventHandle);
        pnlB.addHierarchyListener(eventHandle);
        pnlC.addAncestorListener(eventHandle);
        pnlC.addHierarchyListener(eventHandle);
        setLayout(card);
        add(pnlA, "A");
        add(pnlB, "B");//
        add(pnlC, "C");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    class EventHandler implements AncestorListener, HierarchyListener {

        @Override
        public void ancestorAdded(AncestorEvent event) {
            JComponent comp2 = event.getComponent();
            String str = (String) comp2.getClientProperty("JPanel");
            System.out.println("ancestorAdded " + str);
        }

        @Override
        public void ancestorMoved(AncestorEvent event) {
            JComponent comp2 = event.getComponent();
            String str = (String) comp2.getClientProperty("JPanel");
            System.out.println("ancestorMoved " + str);
        }

        @Override
        public void ancestorRemoved(AncestorEvent event) {
            JComponent comp2 = event.getComponent();
            String str = (String) comp2.getClientProperty("JPanel");
            System.out.println("ancestorRemoved " + str);
        }

        @Override
        public void hierarchyChanged(HierarchyEvent e) {
            JComponent comp2 = (JComponent) e.getComponent();
            String str = (String) comp2.getClientProperty("JPanel");
            System.out.println("hierarchyChanged " + str);
        }
    }

    public static void main(String[] args) {
        CardlayoutTest t = new CardlayoutTest();
        t.setSize(300, 200);
        System.out.println("CardlayoutTest.main()------------------------ FIRST");
        t.card.show(t.getContentPane(), "A");
        t.setVisible(true);
        System.out.print("\n");
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
        }
        System.out.println("CardlayoutTest.main()------------------------ SECOND");
        t.card.show(t.getContentPane(), "B");
        System.out.print("\n");
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
        }
        System.out.println("CardlayoutTest.main()------------------------ THIRD");
        t.card.show(t.getContentPane(), "C");
        System.out.print("\n");
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
        }
        System.out.println("CardlayoutTest.main()------------------------ SECOND");
        t.card.show(t.getContentPane(), "B");
        System.out.print("\n");
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
        }
        System.out.println("CardlayoutTest.main()------------------------ FIRST");
        t.card.show(t.getContentPane(), "A");
        System.out.print("\n");
    }
}

卡布局获取当前卡片串

2 个答案: