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Thread: Traffic Light problems

  1. #1
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    Default Traffic Light problems

    I am working on a program that simulates a traffic light. The program lets the user select one of three lights: red, yellow, or green. When a radio button is selected, the light is turned on, and only one light can be on at a time.
    I have the code written, the only problem that i am having is displaying the traffic light itself. If someone could help me out it would be greatly appreciated.

    Here is what i have coded:

    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;
     
    public class trafficLights extends JFrame {
     
     
    	private JRadioButton jrbRed, jrbYellow, jrbGreen;
    	private boolean jrbRedClicked = false;
    	private boolean jrbYellowClicked = false;
    	private boolean jrbGreenClicked = false;
     
     
    	public static void main(String[] args) {
    		trafficLights frame = new trafficLights();
    		frame.setTitle("Exercise 17_3");
    		frame.setLocationRelativeTo(null);
    		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    		frame.pack();
    		frame.setVisible(true);
    	} // end of main
     
     
    public trafficLights() {
     
    	JPanel jpRadioButtons = new JPanel();
    	jpRadioButtons.setLayout(new FlowLayout());
    	jpRadioButtons.add(jrbRed = new JRadioButton("Red"));
    	jpRadioButtons.add(jrbYellow = new JRadioButton("Yellow"));
    	jpRadioButtons.add(jrbGreen = new JRadioButton("Green"));
    	add(jpRadioButtons, BorderLayout.SOUTH);
     
    	JPanel drawLight = new JPanel();
        drawLight.setLayout(new BorderLayout());
    	add(drawLight, BorderLayout.CENTER);
    	drawLight.add(jpRadioButtons, BorderLayout.SOUTH);
     
     
    	//keyboard mnemonics
    	jrbRed.setMnemonic('R');
    	jrbYellow.setMnemonic('Y');
    	jrbGreen.setMnemonic('G');
     
    	jrbRed.addActionListener(new ActionListener() {
    		public void actionPerformed(ActionEvent e) {
    			if(jrbRed.isSelected())
    			{
    				jrbRedClicked = true;
    				repaint();
    			}
    		}
    	});
    	jrbYellow.addActionListener(new ActionListener() {
    				public void actionPerformed(ActionEvent e) {		
    			if(jrbYellow.isSelected())
    			{
    				jrbYellowClicked = true;
    				repaint();
    			}
    		}
    	});	
    	jrbGreen.addActionListener(new ActionListener() {
    				public void actionPerformed(ActionEvent e) {	
    			if(jrbGreen.isSelected())
    			{
    				jrbGreenClicked = true;
    				repaint();
    			}
    		}
    	}); // end of actionlistener()
     
    } // end of trafficLights()
     
     
    protected void paintComponent(Graphics g) {
    	super.paintComponents(g);
     
    	setBackground(Color.CYAN);
    	g.setColor(Color.BLACK);
    	g.drawRect(260, 50, 80, 160);
    	g.setColor(Color.BLACK);
    	g.drawRect(140, 50, 80, 160);
     
    	if(jrbRedClicked == true)
    	{
    		g.setColor(Color.RED);
    		g.fillOval(280, 60, 40, 40);
    		g.setColor(Color.BLACK);
    		g.drawOval(280, 110, 40, 40);
    		g.drawOval(280, 160, 40, 40);
    		g.drawRect(260, 50, 80, 160);
    		jrbRedClicked = false;
    	}
     
    	if(jrbYellowClicked == true)
    	{
    		g.setColor(Color.YELLOW);
    		g.fillOval(280, 110, 40, 40);
    		g.setColor(Color.BLACK);
    		g.drawOval(280, 50, 80, 160);
    		g.drawOval(280, 160, 40, 40);
    		g.drawRect(260, 50, 80, 160);
    		jrbYellowClicked = false;
    	}
     
    	if(jrbGreenClicked == true)
    	{
    		g.setColor(Color.GREEN);
    		g.fillOval(280, 160, 40, 40);
    		g.setColor(Color.BLACK);
    		g.drawOval(280, 60, 40, 40);
    		g.drawOval(280, 110, 40, 40);
    		g.drawRect(260, 50, 80, 160);
    		jrbGreenClicked = false;
    	}
    }// end of paint component
     
    } // end of public class
    Last edited by sircamolate; November 25th, 2011 at 09:38 PM.


  2. #2
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    Default Re: Traffic Light problems

    Add a call to revalidate? You aren't very specific about the problem.

    Also, never use
    if(boolean == true)
    {
     
    }
    Always do
    if(boolean)
    {
     
    }

  3. #3
    Super Moderator Norm's Avatar
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    Default Re: Traffic Light problems

    Add a println statement to the paintComponent method to be sure it is being called.
    Add a @Override statement just before the paintComponent definition to be sure that the method is overriding correctly.
    Make the size of the frame big enough to display the light in.

  4. #4
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    Default Re: Traffic Light problems

    why should i never do:
    if(boolean == true)
    {
     
    }

    and do:
    if(boolean)
    {
     
    }

    what's the difference in the output/outcome?

  5. #5
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    Default Re: Traffic Light problems

    Quote Originally Posted by sircamolate View Post
    why should i never do:
    if(boolean == true)
    {
     
    }

    and do:
    if(boolean)
    {
     
    }

    what's the difference in the output/outcome?
    Nothing, it's just ugly. Plus it's an additional calculation that you don't have to do. Plus, what if you want to change the meaning of a boolean? You'd have to go back and change all of your if statements to match.
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  6. #6
    Super Moderator Norm's Avatar
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    Default Re: Traffic Light problems

    Plus many students miscode the statement this way:
    if(boolean = true)
    which makes for a hard bug to find.

  7. The Following User Says Thank You to Norm For This Useful Post:

    KevinWorkman (November 28th, 2011)

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