How to use robot class

Question

I have a sort of animation going on in which a rectangle is increasing and decreasing in size........what i want to do here is detect the color of a particular location through Robot() class but its not happening..........why?? I also want to know if Robot() can be used outside try or without main() class.

//<applet code=ctry.java width=500 height=500></applet>

import java.awt.*;
import java.applet.Applet;
import java.awt.AWTException;

public class ctry extends Applet implements Runnable{
Thread d=null;
int l=0,t=0,i=250,j=250;
Color color=null;
public void init(){
 setBackground(Color.red);
                    }
public void start(){
 d=new Thread(this);
 d.start();
                        }
public void run(){
System.out.println("in run");
try{
   Robot robo=new Robot();
  System.out.println("after robo");
  while(true){
      System.out.println("in while");
      repaint();
      color=robo.getPixelColor(i,j);
      System.out.println("Red   = " + color.getRed());
      l+=10;
      t+=10;
      d.sleep(100);    
      if(t>=225)
       {t=0;}
      if(l>=225)
       {l=0;}
                  }

     }
catch(Exception e)
       {}
                         }
public void paint(Graphics g) 
{
System.out.println("in paint");
g.setColor(Color.blue);
g.fill3DRect(225,225,l*2,t*2,true);
}
public void destroy()
{}
}

Rather than writing empty `catch` statements (which is a bad practice) add `print` statements to see if an exception is really thrown — Extreme Coders, May 02 '13 at 09:21
1) Change `catch(Exception e) {}` to `catch(Exception e) { e.printStackTrace(); }` and copy/paste the output as an [edit to the question](http://stackoverflow.com/posts/16334064/edit). Then notify me (by typing the '@' symbol and my name) & I'll have a look over the output. It is likely throwing an `AccessControlException`. 2) Use a consistent and logical indent for code blocks. The indentation of the code is intended to help people understand the program flow! — Andrew Thompson, May 02 '13 at 13:32
@ Andrew Thompson.........the exception is of AccessControlException along with few more...........what now?? — Suraj Pandey, May 02 '13 at 16:42
Edit you question with all the exceptions being thrown. That will help diagnose the problem. — Frecklefoot, May 09 '13 at 16:55
I suspect that `getPixelColor()` may be returning `null`, but I can't be sure. Have you tried stepping through the code with a debugger? How many of your print statements get called? When the exception is thrown, it should give you the line number it's dying on. — Frecklefoot, May 09 '13 at 18:15

score 0 · Answer 1 · answered Jan 29 '14 at 14:31

You could try to capture an image instead and check the color there. The Robot.getPixelColor() is very slow, it returns a new Color instance every time. Try using a BufferedImage instead:

Color color = Color.black;
int screenWidth = 768;
int screenHeight = 1024;
Rectangle rectangle = new Rectangle(screenWidth, screenHeight);
BufferedImage image = robot.createScreenCapture(rectangle);
for (int y = 0 ; y < screenHeight ; y++) {
    for (int x = 0 ; x < screenWidth ; x++) {
        if(image.getRGB(x, y) == color.getRGB()) {
            return true;
        }
    }
}

And yes, you can use the Robot everywhere and you can deal with the exceptions, but most on them are runtime exceptions, so you don't have to.

How to use robot class

1 Answers1