xlis1 xlis1 - 4 months ago 36
Java Question

Can't fix NullPointerException with JTextArea

I am trying to make a text based adventure that runs in a jframe but when i run the program i get a

NullPointer
error on line
97 (first time i append console in the game method)
and I have no idea how to fix it. I am relatively new to
java
so its probably something simple that I just don't know.

my code is here

package window;

import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JButton;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

import javax.swing.JTextArea;
import javax.swing.JTextField;

public class Gui extends JFrame {

public JPanel contentPane;
public static JTextField input;
public static JButton send;
public static JTextArea console;
public static JTextArea invintory;
public static JTextArea stats;
static String i = "";

/**
* Launch the application.
*/



/**
* Create the frame.
*/
public Gui() {
//variables

int Gold = 20;
int Health = 100;
int MaxHealth = 100;


//variables end
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);

JTextArea console = new JTextArea();
console.setBounds(10, 11, 281, 214);
contentPane.add(console);

input = new JTextField();
input.setBounds(10, 236, 281, 20);
contentPane.add(input);
input.setColumns(10);

JTextArea stats = new JTextArea();
stats.setBounds(301, 11, 123, 53);
contentPane.add(stats);

JTextArea invintory = new JTextArea();
invintory.setBounds(301, 75, 128, 137);
contentPane.add(invintory);

JButton send = new JButton("Send");
send.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
String i = input.getText();
input.setText("");
stats.setText("");
stats.append("Health: " + Health + "/" + MaxHealth + "\n");
stats.append("Gold: " + Gold);
}
});
send.setBounds(301, 224, 128, 32);
contentPane.add(send);

stats.append("Health: " + Health + "/" + MaxHealth + "\n");
stats.append("Gold: " + Gold);

}

public static void game (JButton send, JTextArea console, JTextArea stats, JTextArea invintory, JTextField input, String i) {




//start
//START
//START
//START
//START
while (true) {
console.append("You wake up open feild, with vast amounts of wheet in every direction");
console.append("There is a path going in either direction what do you want to do");
console.append("\t1. Go left.");
console.append("\t2. Go right.");
while (i == "") {
}
if (i == "1") {
console.append("1");
break;
}
else if (i == "2") {
console.append("2");
break;
}



}
//END
//END
//END
//END
}

public static void main(String[] args) {
try {
Gui frame = new Gui();
frame.setVisible(true);
Gui.game(send, console, stats, invintory, input, i);
} catch (Exception e) {
e.printStackTrace();
}

}

}

Answer

In your global variable console is null

public static JTextArea console;

You initialized it in Gui method

JTextArea console = new JTextArea();

So here in Gui method your global console variable is not initialized, This creates a local variable console under Gui method.

To initialize global variable in Gui method you need to initialize this way

console = new JTextArea();

You did this mistake to all variables so edit your code this way

public Gui() {
    //variables

    int Gold = 20;
    int Health = 100;
    int MaxHealth = 100;


    //variables end
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 450, 300);
    contentPane = new JPanel();
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    setContentPane(contentPane);
    contentPane.setLayout(null);

    console = new JTextArea();
    console.setBounds(10, 11, 281, 214);
    contentPane.add(console);

    input = new JTextField();
    input.setBounds(10, 236, 281, 20);
    contentPane.add(input);
    input.setColumns(10);

    stats = new JTextArea();
    stats.setBounds(301, 11, 123, 53);
    contentPane.add(stats);

    invintory = new JTextArea();
    invintory.setBounds(301, 75, 128, 137);
    contentPane.add(invintory);

    send = new JButton("Send");
    send.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            String i = input.getText();
            input.setText("");
            stats.setText("");
            stats.append("Health: " + Health + "/" + MaxHealth + "\n");
            stats.append("Gold: " + Gold);
        }
    });
    send.setBounds(301, 224, 128, 32);
    contentPane.add(send);

    stats.append("Health: " + Health + "/" + MaxHealth + "\n");
    stats.append("Gold: " + Gold);

    }