Problem with ScrollPane and JFrame Size

Question

Hi,
The code is workin but after change the size of frame it works CORRECTLY.Please help me why this frame is small an scrollpane doesn't show at the beginning.
Here is the code:
import java.awt.*;
public class canvasExp extends Canvas
     private static final long serialVersionUID = 1L;
     ImageLoader map=new ImageLoader();
    Image img = map.GetImg();
    int h, w;               // the height and width of this canvas
     public void update(Graphics g)
        paint(g);
    public void paint(Graphics g)
            if(img != null)
                 h = getSize().height;
                 System.out.println("h:"+h);
                  w = getSize().width;
                  System.out.println("w:"+w);
                  g.drawRect(0,0, w-1, h-1);     // Draw border
              //  System.out.println("Size= "+this.getSize());
                 g.drawImage(img, 0,0,this.getWidth(),this.getHeight(), this);
                int width = img.getWidth(this);
                //System.out.println("W: "+width);
                int height = img.getHeight(this);
                //System.out.println("H: "+height);
                if(width != -1 && width != getWidth())
                    setSize(width, getHeight());
                if(height != -1 && height != getHeight())
                    setSize(getWidth(), height);
}I create frame here...
import java.awt.*;
import java.awt.event.*;
import javax.swing.JFrame;
public class frame extends JFrame implements MouseMotionListener,MouseListener
     private static final long serialVersionUID = 1L;
    private ScrollPane scrollPane;
    private int dragStartX;
    private int dragStartY;
    private int lastX;
    private int lastY;
    int cordX;
    int cordY;
    canvasExp canvas;
    public frame()
        super("test");
        canvas = new canvasExp();
        canvas.addMouseListener(this);
        canvas.addMouseMotionListener(this);
        scrollPane = new ScrollPane();
        scrollPane.setEnabled(true);
        scrollPane.add(canvas);
        add(scrollPane);
        setSize(300,300);
        pack();
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    public void mousePressed(MouseEvent e)
        dragStartX = e.getX();
        dragStartY = e.getY();
        lastX = getX();
        lastY = getY();
    public void mouseReleased(MouseEvent mouseevent)
    public void mouseClicked(MouseEvent e)
        cordX = e.getX();
        cordY = e.getY();
        System.out.println((new StringBuilder()).append(cordX).append(",").append(cordY).toString());
    public void mouseEntered(MouseEvent mouseevent)
    public void mouseExited(MouseEvent mouseevent)
    public void mouseMoved(MouseEvent mouseevent)
    public void mouseDragged(MouseEvent e)
        if(e.getX() != lastX || e.getY() != lastY)
            Point p = scrollPane.getScrollPosition();
            p.translate(dragStartX - e.getX(), dragStartY - e.getY());
            scrollPane.setScrollPosition(p);
}...and call here
public class main {
     public main(){}
     public static void main (String args[])
         frame f = new frame();
}There is something I couldn't see here.By the way ImageLoader is workin I get the image.
Thank you for your help,please answer me....

Answer 1

I'm not going to even attempt to resolve the problem posted. There are other problems with your code that should take priority.
-- class names by convention start with a capital letter.
-- don't use the name of a common class from the standard API for your custom class, not even with a difference of case. It'll come back to bite you.
-- don't mix awt and Swing components in the same GUI. Change your class that extends Canvas to extend JPanel instead, and override paintComponent(...) instead of paint(...).
-- launch your GUI on the EDT by wrapping it in a SwingUtilities.invokeLater or EventQueue.invokeLater.
-- calling setSize(...) followed by pack() is meaningless. Use one or the other.
-- That's not the correct way to display a component in a scroll pane.
Ah, well, and the problem is that when you call pack(), it retrieves the preferredSize of the components in the JFrame, and you haven't set a preferredSize for the scroll pane.
Please, for your own good, take a break from whatever it is you're working on and go through The Java™ Tutorials: [Creating a GUI with JFC/Swing|http://java.sun.com/docs/books/tutorial/uiswing/TOC.html]
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