Moving shape with arrow keys

Question

Hello,
How would I click on one of the circles I've created and move them using the arrow keys. The circles move just fine with the drag of the mouse but now I want to use the arrow keys. Can somebody help me please? I would really appreciate the assistance.
Michael
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class DragBallPanel extends JPanel implements MouseListener, MouseMotionListener, KeyListener
private static final int BALL_DIAMETER = 50; // Diameter of ball
private static final int BALL_DIAMETER2 = 50;
     //--- instance variables
/** Ball coords. Changed by mouse listeners. Used by paintComponent. */
private int _ballX     = 50;   // x coord - set from drag
private int _ballY     = 50;   // y coord - set from drag
private int x2 = 200;               // starting x coord for 2nd ball
     private int y2 = 200;               //starting y coord for 2nd ball
     private int x3 = 75;
     private int y3 = 150;
/** Position in ball of mouse press to make dragging look better. */
private int _dragFromX = 0;    // pressed this far inside ball's
private int _dragFromY = 0;    // bounding box.
private int xInsideBall = 0;     //coordinates of where the mouse is pressed inside second ball
     private int yInsideBall = 0;     //is pressed inside second ball
     private int x3InsideBall = 0;     //coordinates of where the mouse is pressed inside second ball
     private int y3InsideBall = 0;     //is pressed inside second ball
/** true means mouse was pressed in ball and still in panel.*/
private boolean _canDrag  = false;
     private boolean _canDrag2  = false;
     private boolean _canDrag3  = false;
     /** Constructor sets size, colors, and adds mouse listeners.*/
public DragBallPanel()
          setPreferredSize(new Dimension(400, 400));
setBackground(Color.ORANGE);
setForeground(Color.BLUE);
//--- Add the mouse listeners.
this.addMouseListener(this);
this.addMouseMotionListener(this);
}//endconstructor
     /** Ball is drawn at the last recorded mouse listener coordinates. */
public void paintComponent(Graphics g)
super.paintComponent(g); // Required for background.
g.fillOval(_ballX, ballY, BALLDIAMETER, BALL_DIAMETER);
          g.setColor(Color.RED);
          g.fillOval(x2, y2, BALL_DIAMETER2, BALL_DIAMETER2);
          g.setColor(Color.BLACK);
          g.fillOval(x3, y3, BALL_DIAMETER2, BALL_DIAMETER2);
     }//end paintComponent
     public void mousePressed(MouseEvent e)
int x = e.getX(); // Save the x coord of the click
int y = e.getY(); // Save the y coord of the click
if (x >= ballX && x <= (ballX + BALL_DIAMETER)
&& y >= ballY && y <= (ballY + BALL_DIAMETER))
_canDrag = true;
dragFromX = x - ballX; // how far from left
dragFromY = y - ballY; // how far from top
          else
_canDrag = false;
          //clicked on 2nd ball
          if(x >= x2 && x <= (x2 + BALL_DIAMETER2)
                    && y >= y2 && y <= (y2 + BALL_DIAMETER2) )
               _canDrag2  = true;
               xInsideBall = x - x2;
               yInsideBall = y - y2;
          else
_canDrag2 = false;
          if(x >= x3 && x <= (x3 + BALL_DIAMETER2)
                    && y >= y3 && y <= (y3 + BALL_DIAMETER2) )
               _canDrag3  = true;
               x3InsideBall = x - x3;
               y3InsideBall = y - y3;
          else
_canDrag3 = false;
     }//end mousePressed
     public void mouseDragged(MouseEvent e)
// True only if button was pressed inside ball.
//--- Ball pos from mouse and original click displacement
          if (_canDrag)
ballX = e.getX() - dragFromX;
ballY = e.getY() - dragFromY;
//--- Don't move the ball off the screen sides
ballX = Math.max(ballX, 0);
ballX = Math.min(ballX, getWidth() - BALL_DIAMETER);
//--- Don't move the ball off top or bottom
ballY = Math.max(ballY, 0);
ballY = Math.min(ballY, getHeight() - BALL_DIAMETER);
this.repaint(); // Repaint because position changed.
          if (_canDrag2)
               x2 = e.getX() - xInsideBall;
               y2 = e.getY() - yInsideBall;
               x2 = Math.max(x2, 0);
               x2 = Math.min(x2, getWidth() - BALL_DIAMETER2);
               y2 = Math.max(y2, 0);
               y2 = Math.min(y2, getHeight() - BALL_DIAMETER2);
               this.repaint(); // Repaint because position changed.
          if (_canDrag3)
               x3 = e.getX() - x3InsideBall;
               y3 = e.getY() - y3InsideBall;
               x3 = Math.max(x3, 0);
               x3 = Math.min(x3, getWidth() - BALL_DIAMETER2);
               y3 = Math.max(y3, 0);
               y3 = Math.min(y3, getHeight() - BALL_DIAMETER2);
               this.repaint(); // Repaint because position changed.
}//end mouseDragged
public void keyPressed(KeyEvent ke)
     //int x = e.getX(); // Save the x coord of the click
//int y = e.getY(); // Save the y coord of the click
          int dx = 10;
          switch (ke.getKeyCode())
          case KeyEvent.VK_LEFT: // move x coordinate left
          _ballX -= dx;
          ballX = Math.max(ballX, 0);
          break;
          case KeyEvent.VK_RIGHT: // move x coordinate right
               _ballX += dx;
          ballX = Math.min(ballX, getWidth() - BALL_DIAMETER);
          this.repaint();
public void mouseMoved (MouseEvent e) {} // ignore these events
public void mouseEntered (MouseEvent e) {} // ignore these events
public void mouseClicked (MouseEvent e) {} // ignore these events
public void mouseReleased(MouseEvent e) {} // ignore these events
public void mouseExited (MouseEvent e) {}     // ignore these events
     public void keyReleased (KeyEvent ke) {} // ignore this junk
     public void keyTyped     (KeyEvent ke) {} // ignore this junk
}//endclass DragBallPanel

Answer 1

A couple of notes:
- That code did not add the keyListener to anything.
- At the moment (in the altered code below), only the blue circle moves, and only left/right. It is left as an exercise to the OP to 'take it from there'.
- It only took four more lines of code to turn that code into an SSCCE*, which will generally get more help.
- Please use code indentation, and the code formatting delimiters, when posting code. It makes code a lot easier to read and understand.
* The SSCCE is described at..
<http://www.physci.org/codes/sscce.html>
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class DragBallPanel extends JPanel
  implements MouseListener, MouseMotionListener, KeyListener
  private static final int BALL_DIAMETER = 50; // Diameter of ball
  private static final int BALL_DIAMETER2 = 50;
  //--- instance variables
  /** Ball coords. Changed by mouse listeners. Used by paintComponent. */
  private int _ballX = 50; // x coord - set from drag
  private int _ballY = 50; // y coord - set from drag
  private int x2 = 200; // starting x coord for 2nd ball
  private int y2 = 200; //starting y coord for 2nd ball
  private int x3 = 75;
  private int y3 = 150;
  /** Position in ball of mouse press to make dragging look better. */
  private int _dragFromX = 0; // pressed this far inside ball's
  private int _dragFromY = 0; // bounding box.
  private int xInsideBall = 0; //coordinates of where the mouse is pressed inside second ball
  private int yInsideBall = 0; //is pressed inside second ball
  private int x3InsideBall = 0; //coordinates of where the mouse is pressed inside second ball
  private int y3InsideBall = 0; //is pressed inside second ball
  /** true means mouse was pressed in ball and still in panel.*/
  private boolean _canDrag = false;
  private boolean _canDrag2 = false;
  private boolean _canDrag3 = false;
  /** Constructor sets size, colors, and adds mouse listeners.*/
  public DragBallPanel()
    setPreferredSize(new Dimension(400, 400));
    setBackground(Color.ORANGE);
    setForeground(Color.BLUE);
    //--- Add the mouse listeners.
    this.addMouseListener(this);
    this.addMouseMotionListener(this);
    // add the keylistener!
    this.addKeyListener(this);
    // make sure the panel is focusable
    setFocusable(true);
  }//endconstructor
  /** Ball is drawn at the last recorded mouse listener coordinates. */
  public void paintComponent(Graphics g)
    super.paintComponent(g); // Required for background.
    g.fillOval(_ballX, _ballY, BALL_DIAMETER, BALL_DIAMETER);
    g.setColor(Color.RED);
    g.fillOval(x2, y2, BALL_DIAMETER2, BALL_DIAMETER2);
    g.setColor(Color.BLACK);
    g.fillOval(x3, y3, BALL_DIAMETER2, BALL_DIAMETER2);
  }//end paintComponent
  public void mousePressed(MouseEvent e)
    int x = e.getX(); // Save the x coord of the click
    int y = e.getY(); // Save the y coord of the click
    if (x >= _ballX && x <= (_ballX + BALL_DIAMETER)
    && y >= _ballY && y <= (_ballY + BALL_DIAMETER))
      _canDrag = true;
      _dragFromX = x - _ballX; // how far from left
      _dragFromY = y - _ballY; // how far from top
    else
      _canDrag = false;
    //clicked on 2nd ball
    if(x >= x2 && x <= (x2 + BALL_DIAMETER2)
      && y >= y2 && y <= (y2 + BALL_DIAMETER2) )
      _canDrag2 = true;
      xInsideBall = x - x2;
      yInsideBall = y - y2;
    else
      _canDrag2 = false;
    if(x >= x3 && x <= (x3 + BALL_DIAMETER2)
      && y >= y3 && y <= (y3 + BALL_DIAMETER2) )
      _canDrag3 = true;
      x3InsideBall = x - x3;
      y3InsideBall = y - y3;
    else
      _canDrag3 = false;
  }//end mousePressed
  public void mouseDragged(MouseEvent e)
    // True only if button was pressed inside ball.
    //--- Ball pos from mouse and original click displacement
    if (_canDrag)
      _ballX = e.getX() - _dragFromX;
      _ballY = e.getY() - _dragFromY;
      //--- Don't move the ball off the screen sides
      _ballX = Math.max(_ballX, 0);
      _ballX = Math.min(_ballX, getWidth() - BALL_DIAMETER);
      //--- Don't move the ball off top or bottom
      _ballY = Math.max(_ballY, 0);
      _ballY = Math.min(_ballY, getHeight() - BALL_DIAMETER);
      this.repaint(); // Repaint because position changed.
    if (_canDrag2)
      x2 = e.getX() - xInsideBall;
      y2 = e.getY() - yInsideBall;
      x2 = Math.max(x2, 0);
      x2 = Math.min(x2, getWidth() - BALL_DIAMETER2);
      y2 = Math.max(y2, 0);
      y2 = Math.min(y2, getHeight() - BALL_DIAMETER2);
      this.repaint(); // Repaint because position changed.
    if (_canDrag3)
      x3 = e.getX() - x3InsideBall;
      y3 = e.getY() - y3InsideBall;
      x3 = Math.max(x3, 0);
      x3 = Math.min(x3, getWidth() - BALL_DIAMETER2);
      y3 = Math.max(y3, 0);
      y3 = Math.min(y3, getHeight() - BALL_DIAMETER2);
      this.repaint(); // Repaint because position changed.
  }//end mouseDragged
  public void keyPressed(KeyEvent ke)
    System.out.println("key PRESSED");
    //int x = e.getX(); // Save the x coord of the click
    //int y = e.getY(); // Save the y coord of the click
    int dx = 10;
    switch (ke.getKeyCode())
      case KeyEvent.VK_LEFT: // move x coordinate left
        _ballX -= dx;
        _ballX = Math.max(_ballX, 0);
        break;
      case KeyEvent.VK_RIGHT: // move x coordinate right
        _ballX += dx;
        _ballX = Math.min(_ballX, getWidth() - BALL_DIAMETER);
    this.repaint();
  public void mouseMoved (MouseEvent e) {} // ignore these events
  public void mouseEntered (MouseEvent e) {} // ignore these events
  public void mouseClicked (MouseEvent e) {} // ignore these events
  public void mouseReleased(MouseEvent e) {} // ignore these events
  public void mouseExited (MouseEvent e) {} // ignore these events
  public void keyReleased (KeyEvent ke) {} // ignore this junk
  public void keyTyped (KeyEvent ke) {} // ignore this junk
  /** Add a main(), to make this an SSCCE. */
  public static void main(String[] args) {
    DragBallPanel dbp = new DragBallPanel();
    JOptionPane.showMessageDialog(null, dbp);
}//endclass DragBallPanel