java - 从不同的类加载面板

Question

我有两个类。主类有一个 JFrame 并保存一个按钮，单击该按钮后，它会从不同的类加载一个面板并将其定位在框架的按钮中。

我可以实现它，但我必须重新调整框架大小，然后附加面板才会出现，否则它会被隐藏。

这是我的代码:

public class PanelLoader {

    public static void main(String[] args) {
        // TODO code application logic here
        JFrame frame = new JFrame("Layout");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 300);
        JPanel mainPanel = new JPanel(new BorderLayout());

        JButton press = new JButton("press");
        press.addActionListener(new ActionListener(){ //ActionListener, on click it opens a file choser, 
           @Override                                      //selects a directory then gives it to srcDirField
           public void actionPerformed(java.awt.event.ActionEvent event){
                JPanel mine = ClassWhereStored.newJPanel();
                mainPanel.add(mine, BorderLayout.SOUTH);
           }
        });

        mainPanel.add(press, BorderLayout.NORTH);
        frame.add(mainPanel);

        frame.setVisible(true);
    }
}

二等:

public class ClassWhereStored {
    public static JPanel newJPanel(){
        JPanel panel = new JPanel();
        panel.setBackground(Color.yellow);
        JLabel test= new JLabel("Some Text");
        panel.add(test);
        return panel;
    }
}

那么这个框架有什么问题吗？只有当我重新调整框架大小时才显示附加面板？

Answer 1

使用 CardLayout，添加空白/空 JPanel 和要显示的 JPanel。单击按钮时，只需让 CardLayout 切换面板即可。

参见How to Use CardLayout了解更多详情

例如...

package javaapplication765;

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new BasePane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class BasePane extends JPanel {

        public BasePane() {
            setLayout(new BorderLayout());
            CardLayout cl = new CardLayout();
            JPanel mainView = new JPanel(cl);
            mainView.add(new JPanel(), "empty");
            mainView.add(new BananaPane(), "banana");
            add(mainView);

            JButton btn = new JButton("Fruit loop");
            btn.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    cl.show(mainView, "banana");
                }
            });
            add(btn, BorderLayout.NORTH);
        }

    }

    public class BananaPane extends JPanel {

        public BananaPane() {
            setLayout(new BorderLayout());
            setBorder(new EmptyBorder(25, 25, 25, 25));
            add(new JLabel("I'm a banana"));
        }

    }

}