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Thread: GUI Not Loading

  1. #1
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    Default GUI Not Loading

    I'm trying to make a basic GUI program that computes interest based on a few user-specified values.

    When I run the driver without adding a listener to my buttons, everything works properly, but when I go to add the listener to the button, the GUI doesn't show when I run the driver.

    Driver class:

    package calculator;
     
    import javax.swing.JFrame;
    import javax.swing.WindowConstants;
     
     
    public class InterestGUI {
     
    	public static void createAndShowGUI() {
    		JFrame frame = new JFrame("Interest Calculator");
    		frame.setContentPane(new calcGUI());
    		frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    		frame.pack();
    		frame.setVisible(true);
    	}
     
    	public static void main(String[] args) {
    		javax.swing.SwingUtilities.invokeLater(new Runnable() {
    			public void run() {
    				createAndShowGUI();
    			}
    		});
    	}
    }

    GUI Class
    package calculator;
     
    import javax.swing.JLabel;
    import javax.swing.JPanel;
    import javax.swing.JButton;
    import javax.swing.JTextField;
     
     
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.text.NumberFormat;
     
    public class calcGUI extends JPanel{
     
        private JButton simpleInterestButton = new JButton("Compute Simple Interest");
        private JButton compoundInterestButton = new JButton("Compute Compound Interest");
        private JLabel principal = new JLabel("Principal:");
        private JLabel rate = new JLabel("Rate(Percentage):");
        private JLabel years = new JLabel("Years:");
        private JTextField principalInput = new JTextField(7);
        private JTextField rateInput = new JTextField(7);
        private JTextField yearsInput = new JTextField(7);
        private JLabel interestResult = new JLabel(interestTotal);
        private static String interestTotal;
        private JPanel topPanel = new JPanel();
        private JPanel midPanel = new JPanel();
        private JPanel bottomPanel = new JPanel();
     
    	public class simpleInterestButtonListener implements ActionListener {
    		private String principalValStr = principalInput.getText();
    		private double principalValInt = Integer.parseInt(principalValStr.trim());
    		private String rateValStr = rateInput.getText();
    		private double rateValInt = Integer.parseInt(rateValStr.trim());
    		private String yearsValStr = yearsInput.getText();
    		private double yearsValInt = Integer.parseInt(yearsValStr.trim());
    		private double simpleInterest = 0;
    		private String simpleInterestStr = "";
     
    		public void actionPerformed(ActionEvent arg0) {
    			simpleInterest = principalValInt + (principalValInt*(rateValInt/100)*yearsValInt);
    			simpleInterestStr = NumberFormat.getCurrencyInstance().format(simpleInterest);
    			interestTotal = "Computed simple interest is " + simpleInterestStr;
    		}
    	}
     
    	public calcGUI() {
    		topPanel.add(principal);
    		topPanel.add(principalInput);
    		topPanel.add(rate);
    		topPanel.add(rateInput);
    		topPanel.add(years);
    		topPanel.add(yearsInput);
    		add(topPanel);
    		simpleInterestButton.addActionListener(new simpleInterestButtonListener());
    		midPanel.add(simpleInterestButton);
     
    		compoundInterestButton.addActionListener(new ActionListener() {
    			private String principalValStr = principalInput.getText();
    			private double principalValInt = Integer.parseInt(principalValStr.trim());
    			private String rateValStr = rateInput.getText();
    			private double rateValInt = Integer.parseInt(rateValStr.trim());
    			private String yearsValStr = yearsInput.getText();
    			private double yearsValInt = Integer.parseInt(yearsValStr.trim());
    			private double compoundInterest = 0;
    			private String compoundInterestStr = "";
     
    			public void actionPerformed(ActionEvent arg0) {
    				compoundInterest = (int) (principalValInt*Math.pow((1+rateValInt/100),yearsValInt));
    				compoundInterestStr = NumberFormat.getCurrencyInstance().format(compoundInterest);
    				interestTotal = "Computed simple interest is " + compoundInterestStr;
    			}
    		});
    		midPanel.add(compoundInterestButton);
    		add(midPanel);
    		bottomPanel.add(interestResult);
    		add(bottomPanel);
    	}
    }
    Last edited by ADAMWD; February 23rd, 2011 at 02:15 PM.


  2. #2
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    Default Re: GUI Not Loading

    I figured out that I was placing the variables in the incorrect spot for the button listener class, so now the GUI shows everything properly, except for the interestResult JLabel which is supposed to display the computed interest.

    Right now, nothing happens when either button is pressed. Also, how can I format it so that the buttons are below the text fields, and the interestResult label below the buttons, rather than everything being in a line.

  3. #3
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    Default Re: GUI Not Loading

    Quote Originally Posted by ADAMWD View Post
    Also, how can I format it so that the buttons are below the text fields, and the interestResult label below the buttons, rather than everything being in a line.
    Recommended reading: Lesson: Laying Out Components Within a Container (The Java™ Tutorials > Creating a GUI With JFC/Swing)
    Useful links: How to Ask Questions the Smart Way | Use Code Tags | Java Tutorials
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  4. #4
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    Default Re: GUI Not Loading

    Quote Originally Posted by ADAMWD View Post
    Right now, nothing happens when either button is pressed.
    You want to set the interestTotal into the interestResult label after each calculation.

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