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Thread: defaultCloseOperation doesn't work plus JButttons don't show up

  1. #1
    Junior Member Gugubo's Avatar
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    Default defaultCloseOperation doesn't work plus JButttons don't show up

    So I've got the following code:

    import java.awt.*;
    import javax.swing.*;
     
     
    public class testframe extends JFrame{
     
      private JButton play;
      private JButton highscore;
      private JButton close;
     
     public static void main(String[] args) {
     
      Frame frame = new Frame("Test");
      frame.setSize(600,600);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setLayout(null);
      frame.setVisible(true);
     }
     
     public testframe(String title) {
      super(title);
     
      play = new JButton("Play");
      play.setBounds(120, 40, 160, 40);
      add(play);
     
      highscore = new JButton("Highscores");
      highscore.setBounds(120, 120, 160, 40);
      add(highscore);
     
     
      close = new JButton("Close");
      close.setBounds(120, 200, 160, 40);
      add(close);    
     
     
     }
     
    }

    When I start it, it gives me the following error:

    Exception in thread "main" java.lang.Error: Unresolved compilation problem:
    The method setDefaultCloseOperation(int) is undefined for the type Frame

    at testframe.main(testframe.java:15)

    Then I deleted that line to see if it's the only problem. Now the frame shows up, but there aren't any buttons. It's just an empty window.

    How do I fix this?
    Last edited by Gugubo; October 27th, 2013 at 05:34 AM. Reason: I typed online instead of only. wtf


  2. #2
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    Default Re: defaultCloseOperation doesn't work plus JButttons don't show up

    You made common mistakes, confusing what extending does and created another object. Here are some very minor changes to your code to bring it back in line. I also changed some names to respect Java's naming conventions:
    import java.awt.*;
    import javax.swing.*;
     
    // GB: renamed the class
    public class TestFrame extends JFrame
    {
        private JButton play;
        private JButton highscore;
        private JButton close;
     
        public static void main ( String[] args )
        {
            // GB: new code
            TestFrame frame = new TestFrame( "Test" );
     
            // old code commented out
    //        Frame frame = new Frame ( "Test" );
            frame.setSize ( 600, 600 );
            frame.setDefaultCloseOperation ( JFrame.EXIT_ON_CLOSE );
            frame.setLayout ( null );
            frame.setVisible ( true );
     
        } // end method main()
     
        // GB: renamed the constructor
        public TestFrame ( String title )
        {
            super ( title );
            play = new JButton ( "Play" );
            play.setBounds ( 120, 40, 160, 40 );
            add ( play );
            highscore = new JButton ( "Highscores" );
            highscore.setBounds ( 120, 120, 160, 40 );
            add ( highscore );
            close = new JButton ( "Close" );
            close.setBounds ( 120, 200, 160, 40 );
            add ( close );
     
        } // end constructor
     
    } // end class TestFrame
    This is not the final answer and even all correct as it is, but I respect that you're learning and taking it a step at a time. A habit you should start NOW is starting Swing apps on the EDT by using SwingUtilities.invokeLater() in the main() method to start the Swing app. That'll be in my next post if you keep this one going.

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