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Thread: Problems with ItemEvents

  1. #1
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    Default Problems with ItemEvents

    I'm confused on how to use ItemEvents... the class contains four generic methods that all return generic results if the state of two radio buttons in a menu are changed. How do you use the ItemEvent to simply tell you what is now selected? Or should I be using a regular actionPerformed? Or menuEventListener maybe?

    Also, why is it that JRadioButtonMenuItem inherits the method isSelected from AbstractButton but my compiler says that it can't find the symbol isSelected in class javax.swing.JRadioButtonMenuItem when I try to use it?


  2. #2
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    Default Re: Problems with ItemEvents

    Quote Originally Posted by bgroenks96 View Post
    How do you use the ItemEvent to simply tell you what is now selected?
    I researched this recently and it would seem that the solution is to loop over all buttons to see which is selected. My personal solution was to addan action command to each button. Then call getSelection on the ButtonGroup which returns a ButtonModel. Then call getActionCommand on the Button Model.

    Also, why is it that JRadioButtonMenuItem inherits the method isSelected from AbstractButton but my compiler says that it can't find the symbol isSelected in class javax.swing.JRadioButtonMenuItem when I try to use it?
    Code and full and exact error message or it never happened.

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    Default Re: Problems with ItemEvents

    Quote Originally Posted by Junky View Post
    Code and full and exact error message or it never happened.
    import javax.swing.*;
    import java.awt.event.*;
    class Test {
      JMenu error;
      JMenuBar menuBar;
      ButtonGroup bg;
      JRadioButtonMenuItem one,two;
      public void setUp() {
        JFrame frame = new JFrame();
        JPanel panel = new JPanel();
        menuBar = new JMenuBar();
        error = new JMenu("Error");
        bg = new ButtonGroup();
        one = new JRadioButtonMenuItem("One");
        two = new JRadioButtonMenuItem("Two");
        bg.add(one);
        bg.add(two);
        one.addItemListener(new Listener());
        two.addItemListener(new Listener());
        error.add(one);
        error.add(two);
        menuBar.add(error);
        frame.setJMenuBar(menuBar);
        frame.add(panel);
        frame.setSize(600,600);
        frame.setVisible(true);
      }
      class Listener implements ItemListener {
        public void itemStateChanged(ItemEvent event) {
          if(one.isSelected) {
            System.out.println("One");
          } else if(two.isSelected) {
            System.out.println("Two");
          }
        }
      }
      public static void main(String[] args) {
        Test t = new Test();
        t.setUp();
      }
    }
    javac Test.java
    Test.java:30: cannot find symbol
    symbol : variable isSelected
    location: class javax.swing.JRadioButtonMenuItem
    if(one.isSelected) {
    ^
    Test.java:32: cannot find symbol
    symbol : variable isSelected
    location: class javax.swing.JRadioButtonMenuItem
    } else if(two.isSelected) {
    ^
    2 errors

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    Default Re: Problems with ItemEvents

    Look closely at the code where the error points to - isSelected is a method, not a variable. Variables are accessed via myObject.myVariable Methods as myObject.myMethod()

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    Default Re: Problems with ItemEvents

    Quote Originally Posted by copeg View Post
    Look closely at the code where the error points to - isSelected is a method, not a variable. Variables are accessed via myObject.myVariable Methods as myObject.myMethod()
    Yeah just realized that.... stupidity isn't a fun feeling.

    I do that somewhat often. Type in a method and forget the () identifier.

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    Administrator copeg's Avatar
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    Default Re: Problems with ItemEvents

    Quote Originally Posted by bgroenks96 View Post
    Yeah just realized that.... stupidity isn't a fun feeling.

    I do that somewhat often. Type in a method and forget the () identifier.
    Not stupidity - its called learning. The thing is, I could readily find the error because I myself have done this countless times through the years.

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