The constructor of MainPanel class is not being accessed when I run the app in the full-screen mode. It is only being accessed when I click on any item from the menubar.

The app runs fine in windowed mode or when I manually set the frame's width and height.

app running in windowed-mode or when I set width and height (working fine)

app running in full-screen mode but the MainPanel() constructor is not being called

app running in full-screen mode after clicking on any of the menu item (the MainPanel() constructor in called)

Main.java

    public class Main {
        public static void main(String[] args) {
            AppFrame mainFrame = new AppFrame("Algorithm Visualizer");
            mainFrame.add(new MainPanel());
        }
    }

MainPanel.java

    public class MainPanel extends JPanel {
        MainPanel() {
            this.setBackground(Color.BLACK);
        }
    }

AppFrame.java

    class AppFrame extends JFrame implements ActionListener { 
            private JMenuBar menuBar;
            private JMenu fileMenu, sortingAlgoMenu, searchingAlgoMenu;
            private JMenuItem exitItem, bubbleSortItem;
        
            // constructor with frame_title and auto app resolution
            AppFrame(String frameTitle) {
                // sets the app theme
                setTheme();
        
                // Frame Properties
                this.setTitle(frameTitle);
                this.setDefaultCloseOperation(EXIT_ON_CLOSE);
                this.setResizable(false);
        
                GraphicsDevice myDevice = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice();
            
                // this is the code that makes the frame full-screen
                if(myDevice.isFullScreenSupported()) {
                    this.setUndecorated(true);
                    myDevice.setFullScreenWindow(this);
                }
                else {
                    // windowed mode (title bar present)
                    int deviceWidth = myDevice.getDisplayMode().getWidth();
                    int deviceHeight = myDevice.getDisplayMode().getHeight();
                    
                    this.setSize(deviceWidth, deviceHeight);
                    this.setLocationRelativeTo(null);
                }
        
                // adds the MenuBar
                addMenuBar();
        
                // makes the JFrame visible
                this.setVisible(true);
            }
        
            // constructor passed with app title, width and height
            AppFrame(String frameTitle, int frameWidth, int frameHeight) {
                // sets the app theme
                setTheme();
        
                // Frame Properties
                this.setTitle(frameTitle);
                this.setDefaultCloseOperation(EXIT_ON_CLOSE);
                this.setResizable(false);
                this.setSize(frameWidth, frameHeight);
                this.setLocationRelativeTo(null);
        
                // adds the MenuBar
                addMenuBar();
        
                // makes the JFrame visible
                this.setVisible(true);
            }
        
            // sets the theme of the application
            private static void setTheme() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } 
                catch (ClassNotFoundException e) {
                    e.printStackTrace();
                } 
                catch (InstantiationException e) {
                    e.printStackTrace();
                } 
                catch (IllegalAccessException e) {
                    e.printStackTrace();
                } 
                catch (UnsupportedLookAndFeelException e) {
                    e.printStackTrace();
                }
            }
        
            //  setting the JMenuBar
            private void addMenuBar() {
                menuBar = new JMenuBar();
        
                fileMenu = new JMenu("File");
                menuBar.add(fileMenu);
        
                sortingAlgoMenu = new JMenu("Sorting Algorithms");
                searchingAlgoMenu = new JMenu("Searching Algorithms");
        
                menuBar.add(sortingAlgoMenu);
                menuBar.add(searchingAlgoMenu);
        
                exitItem = new JMenuItem("Exit");
                bubbleSortItem = new JMenuItem("Bubble Sort");
        
                fileMenu.add(exitItem);
                sortingAlgoMenu.add(bubbleSortItem);
        
                // on-click of "Exit" 
                exitItem.addActionListener(this);
        
                this.setJMenuBar(menuBar);
            }
        
            // handle action events (on-click listeners)
            @Override
            public void actionPerformed(ActionEvent e) {
                if(e.getSource() == exitItem)
                    System.exit(0);
            }
        }

CodePudding user response：

Just add the MainPanel in the app frame right before addMenuBar(). The constructor is called anyways but the MainPanel is not visible the other way.

CodePudding user response：

I found what I was doing wrong. I was making the JFrame visible before adding the JPanel. So, I just removed the frame visibility from the AppFrame class and set its visibility(true) from Main.class after adding the JPanel.