CODEWITHSUNDEEP
javaswingargumentsjbuttonactionlistener
fishbone42
fishbone42

Reputation: 21

How to pass an int value to JButton actionlistener?

I'm making a quiz program that asks the user simple math questions, recieves an answer, calculates the user's score, etc...

I'm getting an error because I'm using a variable (in this case, x) inside an actionListener:

for(x = 0;x < total;x++){
System.out.print((x+1)+". ");

questionLabel.setText(number1" + "+ number2);

answerButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e){
            int returnedAns = Integer.parseInt(answerTextField.getText());

                if(returnedAns == answerToTheQuestion){
                    score++;
                    System.out.println("correct");
                    question[x].result = true;
                }else{
                    System.out.println("wrong");
                    question[x].result = false;
                }

                try{
                    Thread.sleep(500);
                }catch(Exception e){}
            }
        });
    }

when i run my code, it highlights int x and says 'local variables referenced from an inner clas must be final or effectively final'.

Please help me out I really don't know what to dowhat to do.

I can't mark it as final as I need to be able to change it for the for loop to work...

Upvotes: 0

Views: 909

Answers (2)

Mitch
Mitch

Reputation: 69

The best way is to define an extra class for this ActionListener implementation.

public class NumberedActionListener implements ActionListener {

  private int number;

  public NumberedActionListener(int number) {
    this.number = number;
  }

  @Override
  public void actionPerformed(ActionEvent e) {
    // ...
  }
}

Then you can pass an int value to the constructor.

answerButton.addActionListener(new NumberedActionListener(x));

This also looks much better if you like clean code...

Upvotes: 3

AesSedai101
AesSedai101

Reputation: 1533

You can assign the value of x to another variable inside the for-loop and then make that variable final.

for(x = 0;x < total;x++){
   final int index = x;
   // use index inside your actionListener
}

Upvotes: 1

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