java - 强制顶部 JPanel 调整大小至其子 JPanel 的高度

Question

我在将顶部 JPanel(这本质上是最顶部的父 JPanel)的高度调整为其子 JPanel 的高度时遇到一些问题。因此，当我将顶部 JPanel 放入网格布局中时，子 JPanel 下方会出现被父 JPanel 占用的额外间隙。我想要做的是消除这个间隙，使顶部 JPanel 的大小与子 JPanel 的大小相同。

本质上，父 JPanel 是一个扩展 JPanel 的类。我尝试使用子 JPanel 的大小将其调整为子 JPanel 的大小，但结果仍然相同。

this.setSize(childJPanel.getSize());

为了澄清，我使用 Matisse 可视化编辑器来编辑这个顶部 JPanel(设置为 GroupLayout)，并且我将此顶部 JPanel 放置到另一个具有 GridLayout 的 JPanel 中。

如何强制顶部 JPanel 调整大小到其子 JPanel 的高度？

代码:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package helloworld;

/**
 *
 * @author Justin
 */
public class FooPanel extends javax.swing.JPanel {

    /**
     * Creates new form NewJPanel
     */
    public FooPanel() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();
        jLabel2 = new javax.swing.JLabel();

        jPanel1.setBorder(javax.swing.BorderFactory.createLineBorder(new java.awt.Color(0, 0, 0)));

        jLabel2.setText("HELLOWORLD");

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jLabel2)
                .addContainerGap(122, Short.MAX_VALUE))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jLabel2)
                .addContainerGap(45, Short.MAX_VALUE))
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
        this.setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        );
    }// </editor-fold>
    // Variables declaration - do not modify
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPanel jPanel1;
    // End of variables declaration
}

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package helloworld;

import java.awt.GridLayout;
import javax.swing.border.EmptyBorder;

/**
 *
 * @author Justin
 */
public class NewJApplet extends javax.swing.JApplet {

    /**
     * Initializes the applet NewJApplet
     */
    @Override
    public void init() {
        /* Set the Nimbus look and feel */
        //<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(NewJApplet.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJApplet.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJApplet.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJApplet.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the applet */
        try {
            java.awt.EventQueue.invokeAndWait(new Runnable() {
                public void run() {
                    initComponents();
                    FooPanel panel1 = new FooPanel();
                    FooPanel panel2 = new FooPanel();
                    FooPanel panel3 = new FooPanel();
                    myPanel.setBorder(new EmptyBorder(5, 5, 5, 5) );
                    myPanel.setLayout(new GridLayout(0,1));
                    myPanel.add(panel1);
                    myPanel.add(panel2);
                    myPanel.add(panel3);

                }
            });
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    /**
     * This method is called from within the init() method to initialize the
     * form. WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        myPanel = new javax.swing.JPanel();

        javax.swing.GroupLayout myPanelLayout = new javax.swing.GroupLayout(myPanel);
        myPanel.setLayout(myPanelLayout);
        myPanelLayout.setHorizontalGroup(
            myPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 200, Short.MAX_VALUE)
        );
        myPanelLayout.setVerticalGroup(
            myPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 300, Short.MAX_VALUE)
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addComponent(myPanel, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(0, 200, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(myPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );
    }// </editor-fold>
    // Variables declaration - do not modify
    private javax.swing.JPanel myPanel;
    // End of variables declaration
}

结果:

Answer 1

正如 Guillaume Polet 上面提到的，事实证明 GridLayout“为其所有子级设置相同的大小(基于可用空间和所有子级的最大首选大小)”。使用 BoxLayout 管理器(特别是 PAGE_LAYOUT)将缓解上述问题。具体来说，BoxLayout 不会将其所有子项设置为相同的大小。我发现此页面对于弄清楚 How to Use BoxLayout 非常有用。 .

使用 BoxLayout 时，可以使用 Glue 和 RigidArea 来分隔组件。