Adding MouseMotionListener to paddle (Java Pong Game)

Question

I searched the entire web trying to find a solution but in the end i just ended up being much more confused and frustrated. I am trying to get my paddle to move (paddle_y). Paddle does not need an x coordinate and it just has to move up and down on the vertical line. I have no idea what syntax i need for the mouseListener to get my paddle to move. please provide an example or solution if possible. Thanks a ton, any help is appreciated.

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


public class PongGame extends JFrame implements Runnable, MouseMotionListener {


  int ball_x, ball_y, ball_dx, ball_dy;
  int ball_r;

  int x_left, x_right, y_top, y_bottom;

  int paddle_y = 30;


  /**
   * Constructor
   */
  public PongGame(){
    init();
  }

  /**
   *  UI
   */
  protected void init(){
    this.setSize(300,300);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);     


    int curX = -1, curY = -1;

    ball_x = this.getWidth()/2;
    ball_y = this.getHeight()/2;

    ball_dx = ball_dy = 2;

    ball_r = 20;

    this.setVisible(true);
    getFocus(this);

    x_left = this.getInsets().left;
    x_right = this.getWidth() - this.getInsets().right - ball_r;
    y_top = this.getHeight() - this.getInsets().top + ball_r/3;
    y_bottom = this.getInsets().bottom + ball_r;

    addMouseMotionListener(this);

  }

    public void mouseMoved(MouseEvent e) {

       //help
    }


    public void mouseDragged(MouseEvent e) {
      //help
    }


  /**
   * helper method which we use to get the focus
   */
  public void getFocus(final JFrame frame)
  {
      EventQueue.invokeLater(new Runnable() {
              public void run() {
                  frame.requestFocus();
              }
       });
  }

  /**
   * implementation of the Runnable interface to be able to move the ball, etc.
   */
  public void run(){

    while(true){

      ball_x += ball_dx;
      if(ball_x <= x_left || ball_x >= x_right){
        ball_dx *=-1;
        ball_x += (2*ball_dx);
      }

      ball_y += ball_dy;
      if(ball_y <= y_bottom || ball_y >= y_top){
        ball_dy *=-1;
        ball_y += (2*ball_dy);
      }

      repaint();

      try{
        Thread.sleep(50);
      }catch(InterruptedException ex){
        System.out.println(ex);
      }
    }
  }

  /**
   * all rendering occurs here
   */
  public void paint(Graphics g){

    //Color paddleOne;
    //paddleOne = new Color(0);

    g.setColor(Color.white);
    g.fillRect(0,0,this.getWidth(),this.getHeight());

    g.setColor(Color.black);
    g.fillOval(ball_x,ball_y, ball_r, ball_r);

    g.setColor(Color.black);
    g.fillRect(0,paddle_y,20,70);
  }

  /**
   * entry point into the program
   */
  public static void main(String[] args){
    // create the class
    PongGame application = new PongGame();
    new Thread(application).start();

  }

}

paddle:

int paddle_y = 30;



g.setColor(Color.black);
g.fillRect(0,paddle_y,20,70);




 public void mouseMoved(MouseEvent e) {

       //help
    }


    public void mouseDragged(MouseEvent e) {
      //help
    }

Answer 1

The Paddle class needs an instance of the JFrame class in order to add a mouse listener. If you pass a JFrame object into the constructor, you can then use the following code:

public class Paddle {
    private JFrame frame;
    private int paddle_y;
    public Paddle(JFrame frame) {
        this.frame = frame;
        this.paddle_y = 30; //Or whatever number you want
        frame.addMouseMotionListener(new MouseMotionListener() {
            public void mouseMoved(MouseEvent e) {
                Paddle.this.paddle_y = e.getY(); //When the mouse is moved, it will call on this function to change the Paddle.paddle_y variable.
            }

            public void mouseDragged(MouseEvent e){} //This reacts when the mouse is clicked, moved, then released.
    }
}

This should replace the Paddle class, and it should change the paddle_y variable when the mouse is moved.

EDIT: If you do not want to create a new class, put this into the JFrame class:

int paddle_y;
this.addMouseMotionListener(new MouseMotionListener() {
                public void mouseMoved(MouseEvent e) {
                    paddle_y = e.getY(); //When the mouse is moved, it will call on this function to change the paddle_y variable (Within the JFrame class).
                }

Then you can call on the paddle_y variable when rendering.