CODEWITHSUNDEEP
javaimageswingjframejpanel
user2588825
user2588825

Reputation: 11

strange thing with inner class JPanel

I tried to override method paintComponent in inner class JPanel and paint some picture. But if I load image in the constructor, method paintComponent is not calling. If load image in main class, everythig is fine. What is it? Here's the code, that does'nt work

import java.awt.Graphics;
import java.awt.Image;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Main {
JFrame window;
//Image image=new ImageIcon("D://domik.png").getImage();

class JPanelExt extends JPanel {
    Image image;

    public JPanelExt (){            
    image=new ImageIcon("D://domik.png").getImage();
    System.out.println("constructor");          
    }

    @Override
    public void paintComponent(Graphics g) {            
        super.paintComponent(g);
        System.out.println("paint");
        g.drawImage(image, 0, 0, this);
        g.drawRect(0, 400, 100, 100);       
    }   
}       

public Main(){

    window=new JFrame("Flowers");
    window.setSize(430, 480);
    window.setVisible(true);
    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);                      
    JPanelExt flower1 =new JPanelExt();
    flower1.setBounds(100, 100, 200, 200);
    flower1.setToolTipText("House");                
    window.setLayout(null);             
    window.add(flower1);                
}   
public static void main(String[] args) {

    Main main=new Main();       
}
}

And sysout writes only "constructor"

But if I change code this way

public class Main {
JFrame window;
Image image=new ImageIcon("D://domik.png").getImage();

class JPanelExt extends JPanel {
    //Image image;

    public JPanelExt (){

    //image=new ImageIcon("D://domik.png").getImage();
    System.out.println("constructor");
             }

    @Override
    public void paintComponent(Graphics g) {

        super.paintComponent(g);
        System.out.println("paint");
        g.drawImage(image, 0, 0, this);
        g.drawRect(0, 400, 100, 100);

    }

And sysout writes "constructor","paint"

I can't understand this ))

Upvotes: 1

Views: 490

Answers (1)

Seelenvirtuose
Seelenvirtuose

Reputation: 20648

Your "problem" is the order of statements in the Main constructor.

First you are constructing a new frame. Second, you set it visible. At this point it is painted and also calls the paint methods on its associated panels. Also at this point, there is no associated panel. Third, you construct a new JPanelExt and add it to the frame. This will not cause the frame to be repainted.

Put the call

window.setVisible(true);

at the end of the construction process. Then you will see your image.

Upvotes: 3

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