JScrollPane update

[R Johnson]

If you change the size of an Object that is a component of JScrollPane what method allows resizing of the scrollbars so that it knows it's looking at a smaller/larger portion of the image?
in my code I tried using paint and revalidate and invalidate none of which gives the desired effect

import javax.swing.*;
import java.awt.image.*;
import java.awt.event.*;
import java.awt.*;
public class DrawingTrial extends JFrame{
    int zoom=1;
    MyMap bi=new MyMap(500,500);
    MyPanel mp=new MyPanel();
    JScrollPane jsp=new JScrollPane(mp);
    MyMouseAdapter mma=new MyMouseAdapter();
    DrawingTrial(){
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(550,550);        
        jsp.setPreferredSize(new Dimension(500,500));        
        mp.addMouseWheelListener(mma);
        mp.addMouseMotionListener(mma);
        mp.addMouseListener(mma);
        getContentPane().setLayout(new FlowLayout());
        getContentPane().add(jsp);
        setVisible(true);
    }
    class MyPanel extends JPanel{
        int width=500;
        int height=500;
        MyPanel(){
            setPreferredSize(new Dimension(width,height));
        }
        @Override
        public void setPreferredSize(Dimension d){
            super.setPreferredSize(d);
            width=d.width;
            height=d.height;
        }
        @Override
        public void paint(Graphics g){
            super.paint(g);
            g.drawImage(bi, 0, 0, width,height,this);
        }
    }
    class MyMap extends BufferedImage{

        MyMap(int width,int height){
            super(width,height,TYPE_INT_ARGB);
            Graphics2D g2=createGraphics();
             g2.setColor(Color.black);
            for(int i=0;i<500;i+=25){
                g2.drawLine(i, 0, i, 500);
                g2.drawLine(0,i,500,i);
            }
            
        }
    }

    class MyMouseAdapter extends MouseAdapter{
        int lastx;
        int lasty;
        @Override
        public void mousePressed(MouseEvent e) {
            System.out.println(e.getY());
            lastx=e.getX()/zoom;
            lasty=e.getY()/zoom;            
        }
        @Override
        public void mouseDragged(MouseEvent e) {            
            Graphics2D g2=bi.createGraphics();
             System.out.println(e.getY());
            int x=e.getX()/zoom;
            int y=e.getY()/zoom;
            g2.setColor(Color.black);
            g2.drawLine(lastx, lasty, x,y);
            g2.dispose();
            System.out.println(lastx+"++__"+lasty);

            jsp.repaint(0,0,500,500);
            lastx=x;
            lasty=y;
            //System.out.println(mp.getPreferredSize().width/500);
            
        }
        @Override
        public void mouseWheelMoved(MouseWheelEvent e) {           
            if(e.isControlDown()){
                System.out.println("Control is down");                
                if(zoom<6 && e.getWheelRotation()==-1){
                    zoom+=1;
                }else if(zoom>1 && e.getWheelRotation()==1){
                    zoom-=1;
                }
                mp.setPreferredSize(new Dimension(zoom*500,zoom*500));
                jsp.repaint(0,0,500,500);
                jsp.invalidate();
                jsp.revalidate();
                
               
            }else{
                jsp.dispatchEvent(e);
            }
        }
    }
public static void main(String[] args){
    new DrawingTrial();
}
}

 

[pete stein]

Have you tried calling revalidate on the viewport?

      @Override
      public void mouseWheelMoved(MouseWheelEvent e) {
         if (e.isControlDown()) {
            System.out.println("Control is down");
            if (zoom < 6 && e.getWheelRotation() == -1) {
               zoom += 1;
            }
            else if (zoom > 1 && e.getWheelRotation() == 1) {
               zoom -= 1;
            }
            mp.setPreferredSize(new Dimension(zoom * 500, zoom * 500));

            //  *** change ***
            jsp.getViewport().revalidate();

            // jsp.repaint(0, 0, 500, 500);
            // jsp.invalidate();
            // jsp.revalidate();

         }
         else {
            jsp.dispatchEvent(e);
         }
      }
   }

[R Johnson]

That works great thanks Pete!