Java swing组件不显示在面板内部

Question

I'm fairly new to swing, so I believe this may be something simple. Hope some of you can give me a hand. This is part of a more complex scenario but I managed to put this in a simple example.

I'm using Netbeans and I'm trying to create a Frame containing a panel with some checkboxes (added dynamically by the frame).

If I use the visual editor to create the entire structure with native components it works well, but the thing is I need a custom panel and this is where it breaks.

When I execute the application, I only see a blank frame with no content.

Code follows

Frame:

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

import java.util.HashSet;
import java.util.Set;
import javax.swing.JButton;
import javax.swing.JCheckBox;

/**
 *
 * @author afsilva
 */
public class Test extends javax.swing.JFrame {

    /**
     * Creates new form Test
     */
    public Test() {
        initComponents();
        this.testPanel1.add(new JCheckBox("ergcdf"));
        this.testPanel1.add(new JCheckBox("ergcdf1"));
        this.testPanel1.add(new JCheckBox("ergcdf2"));
        this.testPanel1.add(new JCheckBox("ergcdf3"));
        this.testPanel1.add(new JCheckBox("ergcdf4"));
        this.testPanel1.validate();
        this.validate();
    }

    /**
     * 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() {

        testPanel1 = new contacorrente.TestPanel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setBackground(new java.awt.Color(51, 204, 255));

        testPanel1.setBackground(new java.awt.Color(255, 51, 204));
        testPanel1.setName("testPanel1"); // NOI18N

        javax.swing.GroupLayout testPanel1Layout = new javax.swing.GroupLayout(testPanel1);
        testPanel1.setLayout(testPanel1Layout);
        testPanel1Layout.setHorizontalGroup(
            testPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 400, Short.MAX_VALUE)
        );
        testPanel1Layout.setVerticalGroup(
            testPanel1Layout.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)
            .addComponent(testPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(testPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );

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

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* 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(Test.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(Test.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(Test.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Test.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Test().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify
    private contacorrente.TestPanel testPanel1;
    // End of variables declaration
}

I'll not paste the panel code since it is simply an empty panel (no custom code)

Help please..

Thanks in advance

Answer 1

Look through the following, it works. I'm not entirely sure what your missing because you're doing it a little differently, but you can look through it. What I'm thinking is is that you're not properly declaring the components. If you're not already, I would suggest Netbeans IDE to do swing. (Netbeans.org)

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

/**
 *
 * @author 
 */
public class NewJFrame extends javax.swing.JFrame {

    /**
     * Creates new form NewJFrame
     */
    public NewJFrame() {
        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();
        jCheckBox1 = new javax.swing.JCheckBox();
        jCheckBox2 = new javax.swing.JCheckBox();
        jCheckBox3 = new javax.swing.JCheckBox();
        jCheckBox4 = new javax.swing.JCheckBox();
        jCheckBox5 = new javax.swing.JCheckBox();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jCheckBox1.setText("ergcdf");

        jCheckBox2.setText("ergcdf1");

        jCheckBox3.setText("ergcdf2");

        jCheckBox4.setText("ergcdf3");

        jCheckBox5.setText("ergcdf4");

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addContainerGap()
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jCheckBox1)
                            .addComponent(jCheckBox2))
                        .addGap(18, 18, 18)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jCheckBox4)
                            .addComponent(jCheckBox3)))
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGap(38, 38, 38)
                        .addComponent(jCheckBox5)))
                .addContainerGap(250, Short.MAX_VALUE))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jCheckBox1)
                    .addComponent(jCheckBox3))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jCheckBox2)
                    .addComponent(jCheckBox4))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(jCheckBox5)
                .addContainerGap(221, Short.MAX_VALUE))
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );

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

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* 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(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new NewJFrame().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    private javax.swing.JCheckBox jCheckBox1;
    private javax.swing.JCheckBox jCheckBox2;
    private javax.swing.JCheckBox jCheckBox3;
    private javax.swing.JCheckBox jCheckBox4;
    private javax.swing.JCheckBox jCheckBox5;
    private javax.swing.JPanel jPanel1;
    // End of variables declaration                   
}

Answer 2

Your JCheckBox es size is 0,0 .

You need to set a size for your JCheckBox es

Your example shown nothing, but if you change your constructor to this:

public Test() {
    initComponents();
    JCheckBox x = new JCheckBox("ergcdf"); //create the component,
    x.setSize(100,30);                     //size the component 
    this.testPanel1.add(x);                //and then add it to the panel
    this.testPanel1.add(new JCheckBox("ergcdf1"));
    this.testPanel1.add(new JCheckBox("ergcdf2"));
    this.testPanel1.add(new JCheckBox("ergcdf3"));
    this.testPanel1.add(new JCheckBox("ergcdf4"));
    this.testPanel1.validate();
    this.validate();
}

It will show the first checkbox. If you set a size to every checkbox you'll see all of them