🚀 go-pugleaf

I had a problem with redrawing the screen in an applet. I have reproduced
the problem using a simple applet that consists of a Choice list
containing "A", "B", "C". When you select from the list, a grid is drawn
below it, containing the letter you selected, replacing any previous grid
that existed. JDK 1.1 AWT is used.

I cant get the grid to display properly from my code when I select from
the Choice list. Under Netscape 4.0.4 with JDK 1.1 update it displays
properly if I press Reload button on browser. Under appletviewer it
displays properly only if I resize the screen. Under IE4 plus SDK 2.0
update it never displays properly.

I have tried placing calls to validate() and paintAll() in the code.
The behaviour still isnt what I expect.

I have seen countless postings to do with similar problems over the last
few months. Is there a definitive answer?

All code for applet is contained below.

regards Geoff Ingram


=========
import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class Draw extends java.applet.Applet
{
	public void init()
	{
		System.out.println("init Draw");
		DrawPanel panel = new DrawPanel();
		add(panel);
	}
}
class DrawPanel extends Panel implements ItemListener
{
	private Choice				mychoice = new Choice();
	private	GridBagLayout		gridbag = new GridBagLayout();
	private	GridBagConstraints  constr	 = new GridBagConstraints();
	private Panel	pnl_grid;

	public	DrawPanel()
	{
		setLayout(gridbag);

		mychoice.addItem("A");
		mychoice.addItem("B");
		mychoice.addItem("C");

		mychoice.addItemListener(this);

		constr.gridwidth = GridBagConstraints.REMAINDER; // end row
		gridbag.setConstraints(mychoice,constr);
		add(mychoice);

	} // DrawPanel

	public void itemStateChanged(ItemEvent evt)
	{
		if (evt.getStateChange() == ItemEvent.DESELECTED)
		{
			return;
		}

		displayGrid(mychoice.getSelectedItem());
	}

	public void displayGrid(String s)
	{
		int dim=1;

		if (s.equals("A"))
			dim=5;
		else if (s.equals("B"))
			dim=4;
		else if (s.equals("C"))
			dim=3;

		GridLayout grid = new GridLayout(dim,dim);

		if (pnl_grid != null) // remove from last time
			remove(pnl_grid);

		pnl_grid = new Panel();
		pnl_grid.setLayout(grid);

		for (int row=0;row<dim;row++)
			for (int col=0;col<dim;col++)
			{
				pnl_grid.add(new Label(s));
			}

		gridbag.setConstraints(pnl_grid,constr);
		add(pnl_grid);
		// paintAll(getGraphics());
	}

} //  DrawPanel

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