CODEWITHSUNDEEP
javaswingjpaneldrawingjscrollpane
dice2289
dice2289

Reputation: 51

Make JScrollPanel dynamically resizable with JPanel drawing

I have a JScrollPanel and a JPanel added to it. I would like to draw to the JPanel and make the scrollbars of the JScrollPane appear whenever the drawing exceeds the size of the panel and be able to scroll the drawing both vertically and horizontally.

I have tried consulting with various forums and the official docs and tried a few things (setting the borders, the preferred size, etc.) but none seems to yield the desired effects.

I have a JFrame (with GridBagLayout, btw.) : 

            JFrame frame1 = new JFrame("Application");
            frame1.setVisible(true);
            frame1.setMinimumSize(new Dimension(580,620));
            frame1.setResizable(false);
            frame1.setLocationRelativeTo(null);
            frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

The relevant components are : 

            JPanel panel1 = new JPanel();
            JScrollPane scrollPane = new JScrollPane(panel1);
            frame1.add(scrollPane, gbc_panel1); //added with layout constraints

JPanel : 

            panel1.setBackground(Color.BLACK);
            panel1.setPreferredSize(new Dimension(500,500));
            panel1.setMinimumSize(new Dimension(360,360));
            panel1.setMaximumSize(new Dimension(1000,1000));

JScrollPane : 

            scrollPane.setAutoscrolls(true);

The relevant code from the action event of a button that does the drawing : 

            Graphics g;
            g = panel1.getGraphics();
            panel1.paint(g);
            g.setColor(new Color(0,128,0));

            /* this is followed by some more code that 
            does the drawing of a maze with g.drawLine() methods */

The code does the drawing perfectly, I just can't seem to figure it out how to make the scrolling and dynamic resizing happen.

I would appreciate any helpful comments or remarks!

Thank you!

Upvotes: 0

Views: 59

Answers (1)

dice2289
dice2289

Reputation: 51

Ultimately rewriting the paint method did the trick as @MadProgrammer suggested. I was just hoping that I could do the painting without having to define my custom JPanel class, but looks like it doesn't work that way.

The custom class looks like this:

class Drawing extends JPanel {

int mazeSize;

public Drawing(JTextField jtf)
{
    try {
    this.mazeSize = Integer.parseInt(jtf.getText());
    }

    catch (Exception e) 
    {
        JOptionPane.showMessageDialog(this, "ERROR!  Invalid size value!");
    }
} // the constructor gets the size of the drawing from a textField

public Dimension getPreferredSize() {
    return new Dimension(mazeSize*10,mazeSize*10);
} //getPreferredSize - this method is used by the scroll pane to adjust its own size automatically

public void drawMaze (Graphics g) 
{
    /* some irrelevant code that does the desired drawing to the panel by calling g.drawLine()*/

} // drawMaze method that does the de facto drawing

@Override
public void paintComponent(Graphics g) 
{
    super.paintComponent(g);
    drawMaze(g);        
}// paintComponent() @Override method - this was the tricky part

}//Drawing JPanel subclass

It is also worth noting (if some noob like myself happens to stumble upon this question), that after instantiating the new JPanel subclass in the action event, I had to add it to the JScrollPanel in the following way, instead of just simply using its add() method:

Drawing drawPanel = new Drawing(textfield1);
scrollPane.getViewport().add(drawPanel);

Again, thanks for the suggestion!

Once finished with the program (a random maze generator that uses a recursive backtracking algorithm), I will make the source code available at my github profile.

Upvotes: 0

Related Questions