Question

Ok, so what i want is the rectangle to always be moving, but when you press the left and right arrow is changes the direction by either increasing or decreasing the angle. With this code the sqaure moves as it should in the correct direction, but when i press the keys the direction does not change.

import java.awt.*;
import java.awt.Color;
import javax.swing.Timer;
import javax.swing.*;
import java.awt.Graphics;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.KeyListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyAdapter;


public class Fields extends JPanel implements ActionListener, KeyListener{

Timer tm  = new Timer(5, this);
double x = 250, y = 250, vel = 0.2, angle = 90;

public void paintComponent(Graphics g)
{
    super.paintComponent(g);
    this.setBackground(Color.BLACK);
    g.setColor(Color.GREEN);
    g.fillRect((int)x, (int)y, 5, 5);

    tm.start();
}
public void keyTyped(KeyEvent e)
{
    if (e.getKeyCode() == 37) {angle--;}
    if (e.getKeyCode() == 39) {angle++;}
}
public void keyReleased(KeyEvent e)
{
    if (e.getKeyCode() == 37) {angle--;}
    if (e.getKeyCode() == 39) {angle++;}
}
public void keyPressed(KeyEvent e)
{
    if (e.getKeyCode() == 37) {angle--;}
    if (e.getKeyCode() == 39) {angle++;}
}
public void actionPerformed(ActionEvent e)
{

    x += (velX * (float)Math.cos(Math.toRadians(angle - 90)));
    y += (velX * (float)Math.sin(Math.toRadians(angle - 90)));

    repaint();
}
public Fields()
{
    this.addKeyListener(this);
}
public static void main(String[] args)
{
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setSize(500, 500);
    Fields fi = new Fields();
    f.add(fi);
    f.setVisible(true);

}
}

Answer 1

As started in my comments…

• Don’t start the timer in paintComponent, this method gets called repeatedly and can be called often in quick succession.
• Use key bindings

.

public class TestAnimation01 {

    public static void main(String[] args) {
        new TestAnimation01();
    }

    public TestAnimation01() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException ex) {
                } catch (InstantiationException ex) {
                } catch (IllegalAccessException ex) {
                } catch (UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new Fields());
                frame.setSize(400, 400);
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class Fields extends JPanel implements ActionListener {

        Timer tm = new Timer(125, this);
        double x = 250, y = 250, vel = 0.2, angle = 90;
        private int velX = 4;
        private int velY = 4;

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            this.setBackground(Color.BLACK);
            g.setColor(Color.GREEN);
            g.fillRect((int) x, (int) y, 5, 5);
        }

        public void actionPerformed(ActionEvent e) {

            x += (velX * (float) Math.cos(Math.toRadians(angle - 90)));
            y += (velX * (float) Math.sin(Math.toRadians(angle - 90)));

            repaint();
        }

        public Fields() {

            setFocusable(true);

            InputMap im = getInputMap(WHEN_FOCUSED);
            ActionMap am = getActionMap();

            // left 37
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), "goLeft");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0), "goRight");

            am.put("goLeft", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    angle--;
                    repaint();
                }
            });
            am.put("goRight", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    angle++;
                    repaint();
                }
            });

            tm.setRepeats(true);
            tm.setCoalesce(true);
            tm.start();

            requestFocusInWindow();

        }
    }
}

There’s a bunch of other things you’ve not covered, such as edge conditions (what happens when it leaves the screen) and individual x/y speeds, but I’m sure you’ll work it out