Question

我有一个JPanel，我用它作为背景，名称是BackgroundPanel。我正在使用NetBeans设计我的主JFrame，并添加像这样的BackgroundPanel。

public class Main extends javax.swing.JFrame {
    Image img = null;
    public Main() {
        initComponents();
        setTitle("Count To");
        setPreferredSize(new Dimension(800, 600));
        Image img = null;
        try {
        img = ImageIO.read(new File("resources/bg.png"));
        } catch (IOException e) {System.out.println("Image can't found.");}

        BackgroundPanel bgPanel = new BackgroundPanel(img, BackgroundPanel.SCALED, 0.0f, 0.0f);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        getContentPane().add(bgPanel);
        pack();
        setVisible(true);
        //setResizable(false);
        setLocationRelativeTo(null);
    }

    /**
     * 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() {

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setCursor(new java.awt.Cursor(java.awt.Cursor.DEFAULT_CURSOR));
        setForeground(java.awt.Color.red);
        setIconImage(getIconImage());

        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>                        

    /**
     * @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(Main.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(Main.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(Main.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Main.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 Main().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    // End of variables declaration                   
}

但是我的BackgroundPanel不可见，即我的框架没有背景图像，而是纯灰色（默认）。

我希望我的解释清楚。如果需要，我也可以包含BackgroundPanel类。

Answer 1

所有顶级容器（和JInternalFrame）都有所谓的“根窗格”。这负责实际构建窗口的主要布局。

根窗格（基本上）包含内容窗格和一个玻璃（和选项菜单栏），它们位于窗口顶部。

enter image description here

当您向窗口添加组件时，它们实际上已添加到内容窗格中。

在您的情况下，仅使用您自己的面板替换内容窗格而不是尝试将其添加到现有面板是有意义的。

这样，当您向窗口添加新组件时，它们实际上会被添加到BackgroundPane。

请确保在尝试向窗口添加任何组件之前更改内容窗格;）

查看How to use Root Panes了解详情

无法将面板（如此背景）添加到我的JFrame

1 个答案: