How to use a robot,it does't work

Question

I would like to mimic keyboard using a Robot.In ButtonFrame,I need to put the focus in the 'blue' button and press it,but though the button has focus but failed to invoke the action.why?help me.ButtonFrame---the background color will change if you click different button related to a different color
package test6;
import javax.swing.*;
import java.awt.*;
import java.awt.event.InputEvent;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
public class RobotTest
   public static void main(String[] args)
      EventQueue.invokeLater(new Runnable()
            public void run()
               // make frame with a button panel
               ButtonFrame frame = new ButtonFrame();
               frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.requestFocus();
               frame.setVisible(true);
               // attach a robot to the screen device
               GraphicsEnvironment environment = GraphicsEnvironment.getLocalGraphicsEnvironment();
               GraphicsDevice screen = environment.getDefaultScreenDevice();
               try
                  Robot robot = new Robot(screen);
                  runTest(robot);
               catch (AWTException e)
                  e.printStackTrace();
    * Runs a sample test procedure
    * @param robot the robot attached to the screen device
   public static void runTest(Robot robot)
      press(robot,KeyEvent.VK_TAB);
      press(robot,' ');
    public static void press(Robot r,int keycode){
        r.keyPress(keycode);
        r.keyRelease(keycode);
class ButtonFrame extends JFrame
   public ButtonFrame()
      setTitle("ButtonTest");
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
      // create buttons
      JButton yellowButton = new JButton("Yellow");
      JButton blueButton = new JButton("Blue");
      JButton redButton = new JButton("Red");
      buttonPanel = new JPanel();
      // add buttons to panel
      buttonPanel.add(yellowButton);
      buttonPanel.add(blueButton);
      buttonPanel.add(redButton);
      // add panel to frame
      add(buttonPanel);
      buttonPanel.setBackground(Color.green);
      // create button actions
      ColorAction yellowAction = new ColorAction(Color.YELLOW);
      ColorAction blueAction = new ColorAction(Color.BLUE);
      ColorAction redAction = new ColorAction(Color.RED);
      // associate actions with buttons
      yellowButton.addActionListener(yellowAction);
      blueButton.addActionListener(blueAction);
      redButton.addActionListener(redAction);
      yellowButton.requestFocus();
    * An action listener that sets the panel's background color.
   private class ColorAction implements ActionListener
      public ColorAction(Color c)
         backgroundColor = c;
      public void actionPerformed(ActionEvent event)
          System.out.println("color:"+backgroundColor);
          buttonPanel.setBackground(backgroundColor);
      private Color backgroundColor;
   private JPanel buttonPanel;
   public static final int DEFAULT_WIDTH = 300;
   public static final int DEFAULT_HEIGHT = 200;
}the app is easy to read,pls finish reading .thxs.

Answer 1

I think the main problem is that the Robot executes to fast. You need a delay between the tab and the space being pressed. I changed you main method to the following:
ButtonFrame frame = new ButtonFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.requestFocus();
frame.setVisible(true);
// attach a robot to the screen device
GraphicsEnvironment environment = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice screen = environment.getDefaultScreenDevice();
try
   Robot robot = new Robot(screen);
   robot.setAutoDelay(500);
   runTest(robot);
catch (AWTException e)
   e.printStackTrace();
}I also use KeyEvent.VK_SPACE.