无法从扩展的 JPanel 中看到 ImageIcon Class

Question

我有一个扩展 JPanel 的 Class，我希望它显示一个 ImageIcon。有些事情似乎没有解决。 map.png 被发现，当我在 class 中打印出它的大小是正确的。另外，我将面板设为黑色，这样我就知道面板可以工作，但 ImageIcon 不行。

然而，当我将来自 TestPanel.java 的相同代码放入 GUI.java 的构造函数时，ImageIcon 起作用了。

有人能告诉我为什么 ImageIcon 在 TestPanel.java 中不起作用但在 GUI.java 中起作用吗？

这是我的代码

TestPanel.java

public class TestPanel extends JPanel {
    
    public static JLabel map = new JLabel();

    public TestPanel() {
        this.setLayout(null); //to prevent icon from taking the whole screen
        this.setVisible(true); //make frame visible
        this.setBounds(0, 0, 100, 100);
        
        this.setBackground(new Color(0,0,0));
        
        Image imageToScale = new ImageIcon("map.png").getImage();
        double scale = .9; //scale
        int x = (int) (imageToScale.getWidth(null) * scale); //leave image observer as null because we know that the image is loaded
        int y = (int) (imageToScale.getHeight(null) * scale);
        Image scaledImage = imageToScale.getScaledInstance( x, y, java.awt.Image.SCALE_SMOOTH); //scale the image
        ImageIcon image = new ImageIcon(scaledImage); //case the image into an image icon
        
        this.setBounds(0, -4, image.getIconWidth(), image.getIconHeight()); //set position and size of panel to the size of the image. -4 on the Y position because it was not aligned with the top
     
        map.setIcon(image); //set icon for map label
        this.add(map); //add label to panel
    }
}

GUI.java

public class GUI extends JFrame {
    
    public static JPanel problemPanel = new JPanel(); //panel where the points and path will be displayed
    public static JLabel map = new JLabel();
    
    public static TestPanel test = new TestPanel();
    
    public GUI() {
        this.setLayout(null); //to prevent icon from taking the whole screen
        
        this.add(test);
        
        //Frame
        this.setVisible(true); //make frame visible
        this.setSize(1200,1000); //set frame size
        this.setTitle("Travelling Apache Pizza Delivery Driver Problem (TAPDDP)"); //set title of panel
        this.setDefaultCloseOperation(this.EXIT_ON_CLOSE); //terminates program when frame is closed
        this.setLocationRelativeTo(null); //open frame in the middle of the screen
        this.setResizable(false); //prevent resizing of GUI
        

    }

}

Answer 1

我通过删除 TestPanel class 中的 this.setLayout(null); 修复了代码。

无法从扩展的 JPanel 中看到 ImageIcon Class

Can't see ImageIcon from an extended JPanel Class

java

swing

awt