Java-JLabel组件仅在调整大小时显示

Question

When I run my code the JFrame Window shows the smallest possible version of the title frame, it needs to be resized in order to actually show anything. Usually this is due to the lack of a pack() or setVisible(true) at the end, but not in this case. This is the code:

public static void main(String[] args) throws FileNotFoundException {
    Boolean[][] maze = Exercise4.readMaze();
    int row = maze.length;

    JFrame f = new JFrame("Maze");
    f.setLayout(new GridLayout(row, row));

    for (int i = 0; i < row; i++) {
        for (int j = 0; j < row; j++) {
            JLabel grid = new JLabel();
            grid.setOpaque(true);
            if (maze[i][j].equals(false))
                grid.setBackground(Color.black);
            else grid.setBackground(Color.white);
            f.add(grid);
        }
    }
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.pack();
    f.setVisible(true);
}

Answer 1

JLabel grid = new JLabel(); is creating a blank label, it's default size will 0x0 , so when you pack the frame, it's been packed down to preferred size of, essentially 0x0

Consider using something like JLabel grid = new JLabel(" "); to start with, but I might consider using a "blank" icon of a specified size instead

You could also use some text and set the foreground (text) color to the same color as the background, but I'd personally use a transparent icon, but that's me

Answer 2

尝试创建一个JPanel并将所有组件放入其中，然后将JPanel添加到JFrame 。