数组和动作监听器Java

Question

Really appreciated the help on the last question, still have a couple of errors however. I am making a treasure Hunt game where the user clicks on a gui to try and reveal the location of a treasure chest. I was using an action listener to display a image of a treasure chest on the button if the location was found but that was a fixed position and I wanted to randomise this. Got some advice to use an array on buttons and random number generator then use an if/else to check. Having complier errors which I will comment on the code below. A good coder will probably pick my novice errors up in a matter of seconds!

    import java.awt.*;
    import javax.swing.*;
    import java.util.Random;
    import java.awt.event.ActionListener;
    import java.awt.event.ActionEvent;



  public class Test extends JFrame {


     JLabel label1, label2, label3;    

    ImageIcon image1, image2, image3, image4, image5;


 JTextField textResult;    

  public static void main(String[] args) {



  new Test();

    }


   public Test (){

  this.setSize(700,700);
  this.setLocationRelativeTo(null);
  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  this.setTitle("Treasure Hunt Game");

  JPanel thePanel = new JPanel();


  thePanel.setLayout(new GridLayout(0,3,0,0));

  image1 = new ImageIcon(getClass().getResource("Treasure.jpg"));
  image2 = new ImageIcon(getClass().getResource("Pirate.jpg"));
  image3 = new ImageIcon(getClass().getResource("sand2.jpg"));
  image4 = new ImageIcon(getClass().getResource("emptyhole.jpg"));   
  image5 = new ImageIcon(getClass().getResource("map.jpg"));

  label1 = new JLabel("Click the buttons to find the Treasure!");
  label2 = new JLabel(image5); 
  label3 = new JLabel(image2);


  JButton [] buttons = new JButton[9]; 
  buttons[0] = new JButton(image3);
  buttons[1] = new JButton(image3);
  buttons[2] = new JButton(image3);
  buttons[3] = new JButton(image3);
  buttons[4] = new JButton(image3);
  buttons[5] = new JButton(image3);
  buttons[6] = new JButton(image3);
  buttons[7] = new JButton(image3);
  buttons[8] = new JButton(image3);


  thePanel.add(buttons[0]);
  thePanel.add(buttons[1]);
  thePanel.add(buttons[2]);
  thePanel.add(buttons[3]);
  thePanel.add(buttons[4]);
  thePanel.add(buttons[5]);
  thePanel.add(buttons[6]);
  thePanel.add(buttons[7]);
  thePanel.add(buttons[8]);
  thePanel.add(label1); 
  thePanel.add(label2);
  thePanel.add(label3);



  this.add(thePanel);

  this.setVisible(true);


  int treasureLocation = new Random().nextInt(buttons.length);


  System.out.println(treasureLocation);

On the complier, it gives me a error message saying it does not know the "buttons" or "treasureLocation" in the if else statement below.

        }
       public void actionPerformed(ActionEvent evt) {
      if (evt.getSource() == buttons[treasureLocation]) {
      }

  else {

  }

  } 

}

Answer 1

Is it possible you have a different Listener class?

public class Test extends JFrame {

    public Test(){
        Button[] buttons;
        int treasureLocation;
    }

    private class ButtonListener implements ActionListener{
        public void actionPerformed(ActionEvent e) {
            if (evt.getSource() == buttons[treasureLocation]) {
        }
    }
}

This would cause an error as buttons and treasureLocation are not within the scope. If this is not the case, it still seems like a scope issue to me. Try declaring the variables as class members

public class Test extends JFrame {
    Button[] buttons;
    int treasureLocation;

    public Test(){

    }
}

Answer 2

You actually defined buttons and treasureLocation in your constructor, which is actually not recommended. Their lifecycle and access is therefore limited to this method. Define them in your class and initialize them.

Answer 3

JLabel label1, label2, label3;    
ImageIcon image1, image2, image3, image4, image5;
JTextField textResult;
JButton [] buttons; // Move the declaration here
int treasureLocation; // Move the declaration here

and change

JButton [] buttons = new JButton[9]; 

to

buttons = new JButton[9]; 

and

int treasureLocation = new Random().nextInt(buttons.length);

to

treasureLocation = new Random().nextInt(buttons.length);

Answer 4

You need to have buttons and treasureLocation defined as attributes. So don't define them in a method or a constructor, have them defined in the line after

ImageIcon image1, image2, image3, image4, image5;