Problem with multiple keys pressed

I'm having an issue with some code I'm just playing around with. Imagine a top down space shooter. The issue I'm having is that, on my computer, when I press and hold the up and left arrows, I cannot shoot (Spacebar). Any other direction (up, down, left, right, up + right, right + down, left + down) works. I had a friend run the code on his computer and he found that all directions worked except up + right and right + down, but up + left worked fine for him. We both looked at the code and can't figure it out.

Could this be a hardware issue?

Basically, this is what I'm doing:

import javax.swing.*;
import java.awt.event.*;

public class Test extends JFrame
{
	boolean up, down, left, right, fire;

// Main constructor
	public Test()
	{
		// listeners for user input
		this.addKeyListener(new KeyAdapter()
		{
			public void keyPressed(KeyEvent e)
			{
				switch (e.getKeyCode())
				{
					case KeyEvent.VK_UP:
					{
						up = true;
						break;
					}

case KeyEvent.VK_LEFT:
					{
						left = true;
						break;
					}

case KeyEvent.VK_RIGHT:
					{
						right = true;
						break;
					}

case KeyEvent.VK_DOWN:
					{
						down = true;
						break;
					}

case KeyEvent.VK_SPACE:
					{
						fire = true;
						break;
					}

case KeyEvent.VK_ESCAPE:
					{
						// Exit
						System.exit(0);
					}
				}
			}

public void keyReleased(KeyEvent e)
			{
				// Upon releasing key, stop direction
				switch(e.getKeyCode())
				{
					case KeyEvent.VK_UP:
					{
						up = false;
						break;
					}

case KeyEvent.VK_LEFT:
					{
						left = false;
						break;
					}

case KeyEvent.VK_RIGHT:
					{
						right = false;
						break;
					}

case KeyEvent.VK_DOWN:
					{
						down = false;
						break;
					}
				}
			}
		});
	}

public static void main(String[] args)
	{
			// create frame
			Test test = new Test();
			test.setLocationRelativeTo(null);
			test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
			test.setVisible(true);
			test.loop();
	}

public void loop()
	{
		Timer timer = new Timer(250, new ActionListener()
		{
			public void actionPerformed(ActionEvent e)
			{
				if (up)
					System.out.println("Moving UP.");
				if (left)
					System.out.println("Moving LEFT.");
				if (right)
					System.out.println("Moving RIGHT.");
				if (down)
					System.out.println("Moving DOWN.");
				if (fire)
				{
					System.out.println("FIRING.");
					fire = false;
				}
			}
		});

timer.start();
	}
}

Yes, I believe it's actually a keyboard limitation. Try running on the same computer with a different keyboard.

well, i think you should try this:

i use a whole different method , but i prefer this one

post this in your keypressed method be sure to make it KeyEvent e

be sure to copy this code also in the keyreleased, set the booleans to false.
you might ask UP,DOWN,LEFT,RIGHT?
just add this in your script:

Timer timer = new Timer(250, new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
if (up)
System.out.println("Moving UP.");
if (left)
System.out.println("Moving LEFT.");
if (right)
System.out.println("Moving RIGHT.");
if (down)
System.out.println("Moving DOWN.");
if (fire)
{
System.out.println("FIRING.");
fire = false;
}
}
});

Also, you are missing a bracket and ; on line 109 I think it is, they are actually on line 119, dunno if that's just an upload error or if it's coded like that.

Niall

tom klu wrote:well, i think you should try this:

i use a whole different method , but i prefer this one
post this in your keypressed method be sure to make it KeyEvent e

int key = e.getKeyCode(); if(key == UP)up=true; if(key == DOWN)down=true; if(key == LEFT)left=true; if(key == RIGHT)right =true;
be sure to copy this code also in the keyreleased, set the booleans to false.
you might ask UP,DOWN,LEFT,RIGHT?
just add this in your script:
int UP = KeyEvent.VK_UP; int DOWN = KeyEvent.VK_DOWN; int RIGHT = KeyEvent.VK_RIGHT; int LEFT = KeyEvent.VK_LEFT;

I tried your code but I still had the same issue. What's the preferred method to handle this in games? Surely there must be a solution.

well you might try making booleans..... this will def. work or otherwise it must be your keyboard.

Stephan van Hulst wrote:Yes, I believe it's actually a keyboard limitation. Try running on the same computer with a different keyboard.

I did try a different keyboard but had the same results. The same key combination did not work.

tom klu wrote:well you might try making booleans..... this will def. work or otherwise it must be your keyboard.
public boolean Keys[] = new boolean[40]; public final int UP = 0; public final int DOWN = 2; public final int RIGHT = 3; public final int LEFT = 4; public final int SHOOT = 5; public final int JUMP = 6; public void set(int key, boolean b){ int B = -1; if(key == KeyEvent.VK_UP)B = UP; if(key == KeyEvent.VK_DOWN)B = DOWN; if(key == KeyEvent.VK_LEFT)B = LEFT; if(key == KeyEvent.VK_RIGHT)B = RIGHT; if(key == KeyEvent.VK_W)B = UP; if(key == KeyEvent.VK_S)B = DOWN; if(key == KeyEvent.VK_A)B = LEFT; if(key == KeyEvent.VK_D)B = RIGHT; if(key == KeyEvent.VK_SPACE)B = SHOOT; if(key == KeyEvent.VK_X)B = JUMP; if(key == KeyEvent.VK_S)B = STUCK; if(key == KeyEvent.VK_A)B = UNSTUCK; if(B >= 0 || B == 0){ Keys[B] = b; } }

I downloaded a top down space shooter programmed in Java and had no issues moving up and left and firing. However, movement used WASD instead of the arrow keys - as does your code above. It now works using WASD so it must be an issue with using the arrow keys and spacebar at the same time.