3 replies to this topic

[Plutonic]

Hey I was wondering if anyone could tell me how I would use input such as typing a key to change an int variable? Everything I've tried so far compiles fine but the variable still doesn't change.

[John]

Post what you have tried

[Plutonic]

Ok so far I've tried using the getKeyCode method in the keyPressed and keyReleased methods. eg:

public void keyPressed(KeyEvent input) {

int key = input.getKeyCode();
if (key == 68)
p1xMove = 1;
}

public void keyPressed(KeyEvent input) {

char key = input.getKeyChar();
if (key == 'd')
p1xMove = 1;
}

Where p1xMove is an int variable I've set up earlier. I've even tried using boolean variables but it still doesn't work!

[John]

Well here are a few things to keep in mind.

1. You have to implement the KeyListener class
2. You have to add a KeyListener to a component [maybe the main frame]
3. Make sure the instance variable is initialized
4. Make sure you change the variable to something different other than what it was initialized to.
5. If your using the key to update a text value in a component, make sure you repaint the component.

Since you didn't provide the entire class, I cant check for these. But here is a small demo I just created.

package net.codecall.forums;

import java.awt.Dimension;

import java.awt.event.KeyEvent;

import java.awt.event.KeyListener;

import javax.swing.JFrame;

import javax.swing.JLabel;

public class ButtonListener implements KeyListener{

	//Instance Variable

	private int i = 0;

	private JLabel label;	

	public ButtonListener() {

		//create a new JFrame

		JFrame frame = new JFrame("Key Listener");

		//set the dimensions

		frame.setPreferredSize(new Dimension(200, 200));

		/******   ADD AN ACTION LISTENER TO THE FRAME   ******/

		frame.addKeyListener(this);		

		//create a new JLabel

		label = new JLabel();

		//set the text on the label

		label.setText(String.valueOf(i));

		//add the label

		frame.add(label);

		//make the frame visible

		frame.setVisible(true);

		//set the default close operation

		frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);

		//pack the frame

		frame.pack();		

	}

	public void keyPressed(KeyEvent e) {

		//If the key D was pressed

		if(e.getKeyCode() == 68){

			//increase i by one

			i++;

			//'repaint' the label

			label.setText(String.valueOf(i));

			//and output the value to the console

			System.out.println(i);

		}

	}

	public void keyReleased(KeyEvent e) {	}

	public void keyTyped(KeyEvent arg0) {	}	

	public static void main(String[] args){

		new ButtonListener();

	}

}