我不明白为什么图像不在JPanel中显示但在JFrame中正常显示的原因

Question

I am creating a simple program in which I want to display an Image and a button.So I've created a JFrame .

This JFrame contains tow JPanel and one of the panels contains JButton and the other panel contains my image. But image is not displaying in the panel. When I add image to the JFrame , it is displaying normally. Please help with the following code!

main() method:

public class NewClass2 {
public static void main(String args[]){

    EventQueue.invokeLater(new Runnable(){
        public void run(){
            JFrame frm = new JFrm();
            frm.setVisible(true);
            frm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frm.setSize(500,500);
        }
    });

}
}

JFrm class which initialize JFrame :

class JFrm extends JFrame{

JButton button;
JPanel panel0,panel1;

JFrm(){

    panel0 = new JPanel();
    panel1 = new JPanel();
    button = new JButton("Start");
    button.setPreferredSize(new Dimension(100, 30));
    panel0.add(button);

  panel1.add(new ImageComponent());   //adding image component to panel1 is not working
  //add(new ImageComponent());      //adding image component to the frame is working .. 


    add(panel1,BorderLayout.PAGE_START);
    add(panel0,BorderLayout.PAGE_END);

}

}

ImageComponent class which adds the image:

class ImageComponent extends JComponent{
Image img;
ImageComponent(){
    img = new ImageIcon("C:\\Users\\Kaushal28\\Desktop\\Aqua-Ball-icon.png").getImage();

}


@Override
public void paint(Graphics g){

    g.drawImage(img, 100,100 , null);
}

}

How can I add image to JPanel ?

Answer 1

Consider wrapping the image in a JLabel before adding it to the JPanel. See Display a jpg image on a JPanel

class JFrm extends JFrame{

JButton button;
JPanel panel0, panel1;

JFrm(){

    panel0 = new JPanel();
    panel1 = new JPanel();
    button = new JButton("Start");
    button.setPreferredSize(new Dimension(100, 30));
    panel0.add(button);

    ImageIcon image = new ImageIcon("C:\\Users\\Kaushal28\\Desktop\\Aqua-Ball-icon.png");
    panel1.add(new JLabel(image));

    add(panel1, BorderLayout.PAGE_START);
    add(panel0, BorderLayout.PAGE_END);

}
}

Answer 2

You did not set a size for your custom JComponent so it'll be squished by the LayoutManager to zero size. Use setPreferredSize() to set whatever size seems suitable.

ImageComponent(){
    ImageIcon temp = new ImageIcon("test.png");
    img = temp.getImage();
    setPreferredSize(new Dimension(temp.getIconWidth(),temp.getIconHeight()));
}


@Override
public void paint(Graphics g){
    g.drawImage(img, 0,0 , null);
}