为什么在我的 JScrollPane 上更改大小时更改 JPanel 中的对象（JPanel）？

Question

每当我更改这行代码时：

scrollPane.setSize(new Dimension(500, 500));

到

scrollPane.setSize(new Dimension(500, 600));

我的 JPanel 中的对象 (JPanel) 发生了变化？

一种查看结构的方法是：

Objects: JScrollPanel(  JPanel          (    JPanel( )    )     );
names:   scrollPanel (  tableCollection (    table1( )    )     )

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Insets;
import java.awt.Toolkit;
import javax.swing.JPanel;
import javax.swing.JScrollPane;


public class testing extends javax.swing.JFrame {

    public testing () {
        initComponents();

        setMainFrameSize();
        addScrollPane();
        addTables();
    }

    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        addComponentListener(new java.awt.event.ComponentAdapter() {
            public void componentResized(java.awt.event.ComponentEvent evt) {
                formComponentResized(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 400, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 300, Short.MAX_VALUE)
        );

        pack();
    }// </editor-fold>                        

    private void formComponentResized(java.awt.event.ComponentEvent evt) {                                      
        setScrollPaneSize();
        setTableSize();
    }                                     

    public static void main(String args[]) {
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(testing.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(testing.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(testing.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(testing.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new testing().setVisible(true);
            }
        });
    }

    JPanel tableCollection = new JPanel();
    JScrollPane scrollPane = new JScrollPane(tableCollection, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
                                             JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);

    // Variables declaration - do not modify                     
    // End of variables declaration                   

    void setMainFrameSize() {
        this.setMinimumSize(new Dimension(800, 600));
        Dimension scnDimension = Toolkit.getDefaultToolkit().getScreenSize();
        Insets scnInsets = Toolkit.getDefaultToolkit().getScreenInsets(getGraphicsConfiguration());
        this.setSize(scnDimension.width, scnDimension.height-(scnInsets.bottom+scnInsets.top));
    }

    void addScrollPane() {
        scrollPane.setBackground(Color.red);
        setScrollPaneSize();
        this.add(scrollPane);

        addTableCollection();
    }
    void setScrollPaneSize() {
        scrollPane.setSize(new Dimension(500, 500));
        scrollPane.setLocation(0, barHeight);
    }

    void addTableCollection() {
        tableCollection.setBackground(new Color(189, 195, 199));
        setTableCollectionSize();
    }
    void setTableCollectionSize() {
        tableCollection.setPreferredSize(new Dimension(550, 550));
    }

    void addTables() {
        table1.setBackground(new Color(52, 152, 219));

        tableCollection.add(table1);

    }
    void setTableSize() {

        int tableHeight = tableCollection.getHeight()-tableHeightOffset*2;
        table1.setSize(350, tableHeight);
        table1.setLocation(0, 0);
    }

    int barHeight = 50;
    int tableHeightOffset = 50;
    int tableWidthOffset = 50;
    int nTables = 5;

    JPanel table1 = new JPanel();

}

Answer 1

只需添加 tableCollection.setLayout(null); 以便它可以处理 JPanel 中的自定义大小的 JPanel

谢谢乔纳斯 JPanel inside another

为什么在我的 JScrollPane 上更改大小时更改 JPanel 中的对象（JPanel）？

Why when changing the size on my JScrollPanel changes my object (a JPanel) inside JPanel?

java

swing

jpanel

jscrollpane