import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)

/**
 * Write a description of class poi here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class poi extends Actor
{

        public final String LETTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";  
        public final String letters = "abcdefghijklmnopqrstuvwxyz";  
        public final String Numbers = "0123456789";  
        public final String Symbols = "`~!@#$%^&*()_+-=[]{}|;':<>?,./";  
        public String txtString = "";  

        public void act()  
        {  
            String myKey = Greenfoot.getKey();  
            if (myKey == null) { return; }  
            String myText = "";  
            if (myKey == "space") { myKey = " "; } // If spaces are not wanted, change 'myKey = " ";' to 'return;'  
            if (myKey == "backspace")  
            {  
                // Code for when 'backspace' is pressed  
                if (txtString.length() > 0)  
                {  
                    txtString = txtString.substring(0, txtString.length() - 1);  
                }  
                return;  
            }  
            if (myKey == "enter")  
            {  
                // Code for when 'enter' is pressed  
                return;  
            }  
            // You can continue for other keys: arrow keys, function keys, 'tab' and 'escape' (and any others I may have missed)  

            // Change the concatenation in the following statement to only wanted characters  
            String goodChars = LETTERS + letters + Numbers + Symbols + " ";  
            int myIndex = goodChars.indexOf(myKey.charAt(0));  
            if (myIndex > -1)  
            {  
                myText = goodChars.substring(myIndex, myIndex + 1);  
                txtString = txtString + myText;  
            }  
            new GreenfootImage(70, 60);
           // wrong method?
drawString(txtString, 60, 50);
            setImage(txtString);
        }
    }    

GreenfootImage image = new GreenfootImage(70,60);
image.drawString(txtString, 10, 10);
setImage(image);