MouseMoved事件

Question

What im trying to do is I draw the image, and then I use this method to hide and draw the image again where the mouse at.

the problem im facing that I still get some little stuff from the old image which it doesn't hide the picture completely, when I try it with different methods like "KeyPressed" everything works well.

is this the right method to do the mouse event? or this code is incorrect?

public class GameFrame extends javax.swing.JFrame implements java.awt.event.ActionListener
{

   private java.util.Vector<Milk> foodList = new java.util.Vector<Milk>();
   private javax.swing.Timer moveTimer = new javax.swing.Timer(500, this);
   private MotherFigure motherFig;
   private BabyFigure babyFig;
   private FastFood burgerFig;
   private int speedTrack = 200;
   private int milkCount = 1;

   @Override
   public void actionPerformed(ActionEvent ae)
   {
      motherFig.draw();
      babyFig.draw();
      moveFood();
      collided();
      motherFig.hide();
   }

   /**
    * Creates new form GameFrame
    */
   public GameFrame()
   {
      initComponents();
      motherFig = new MotherFigure(gamePanel);
      babyFig = new BabyFigure(gamePanel);
      burgerFig = new FastFood(gamePanel);
      moveTimer.start();
      gamePanel.requestFocus();
   }

   /**
    * This method is called from within the constructor to initialize the
    * form. WARNING: Do NOT modify this code. The content of this method is
    * always regenerated by the Form Editor.
    */
   @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        gamePanel = new javax.swing.JPanel();
        txtCount = new javax.swing.JTextField();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setBackground(new java.awt.Color(255, 255, 255));
        setCursor(new java.awt.Cursor(java.awt.Cursor.WAIT_CURSOR));
        getContentPane().setLayout(null);

        gamePanel.setBackground(new java.awt.Color(255, 255, 255));
        gamePanel.addMouseMotionListener(new java.awt.event.MouseMotionAdapter() {
            public void mouseMoved(java.awt.event.MouseEvent evt) {
                gamePanelMouseMoved(evt);
            }
        });
        gamePanel.addFocusListener(new java.awt.event.FocusAdapter() {
            public void focusGained(java.awt.event.FocusEvent evt) {
                gamePanelFocusGained(evt);
            }
        });
        gamePanel.addKeyListener(new java.awt.event.KeyAdapter() {
            public void keyPressed(java.awt.event.KeyEvent evt) {
                gamePanelKeyPressed(evt);
            }
        });

        txtCount.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        txtCount.setBorder(null);
        txtCount.setCursor(new java.awt.Cursor(java.awt.Cursor.TEXT_CURSOR));
        txtCount.setSelectionColor(new java.awt.Color(255, 255, 255));

        javax.swing.GroupLayout gamePanelLayout = new javax.swing.GroupLayout(gamePanel);
        gamePanel.setLayout(gamePanelLayout);
        gamePanelLayout.setHorizontalGroup(
            gamePanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, gamePanelLayout.createSequentialGroup()
                .addContainerGap(596, Short.MAX_VALUE)
                .addComponent(txtCount, javax.swing.GroupLayout.PREFERRED_SIZE, 98, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap())
        );
        gamePanelLayout.setVerticalGroup(
            gamePanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(gamePanelLayout.createSequentialGroup()
                .addContainerGap()
                .addComponent(txtCount, javax.swing.GroupLayout.PREFERRED_SIZE, 29, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(545, Short.MAX_VALUE))
        );

        getContentPane().add(gamePanel);
        gamePanel.setBounds(80, 10, 700, 580);

        pack();
    }// </editor-fold>                        

   private void gamePanelKeyPressed(java.awt.event.KeyEvent evt)                                     
   {                                         
      if (evt.getKeyCode() == java.awt.event.KeyEvent.VK_LEFT)
         motherFig.move(-10, 0); //babyFig.move(-10, 0);
      else if (evt.getKeyCode() == java.awt.event.KeyEvent.VK_RIGHT)
         motherFig.move(10, 0); //babyFig.move(10, 0);
      motherFig.draw();

   }                                    

   private void gamePanelFocusGained(java.awt.event.FocusEvent evt)                                      
   {                                          
      // TODO add your handling code here:
      txtCount.setText("Milk Catched: ");
      Milk b = new Milk(gamePanel);
      b.draw();
      foodList.add(b);
   }                                     

    private void gamePanelMouseMoved(java.awt.event.MouseEvent evt) {                                     
       motherFig.hide();
       int X = evt.getX();
       int Y = evt.getY();
       motherFig.move(X, Y);
       motherFig.reDraw(X, Y);

    }                                    

   /**
    * @param args the command line arguments
    */
   public static void main(String args[])
   {
      /*
       * Set the Nimbus look and feel
       */
      //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /*
       * If Nimbus (introduced in Java SE 6) is not available, stay with the
       * default look and feel. For details see
       * http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
       */
      try
      {
         for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels())
         {
            if ("Nimbus".equals(info.getName()))
            {
               javax.swing.UIManager.setLookAndFeel(info.getClassName());
               break;
            }
         }
      }
      catch (ClassNotFoundException ex)
      {
         java.util.logging.Logger.getLogger(GameFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
      }
      catch (InstantiationException ex)
      {
         java.util.logging.Logger.getLogger(GameFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
      }
      catch (IllegalAccessException ex)
      {
         java.util.logging.Logger.getLogger(GameFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
      }
      catch (javax.swing.UnsupportedLookAndFeelException ex)
      {
         java.util.logging.Logger.getLogger(GameFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
      }
      //</editor-fold>

      /*
       * Create and display the form
       */
      java.awt.EventQueue.invokeLater(new Runnable()
      {

         @Override
         public void run()
         {
            new GameFrame().setVisible(true);
         }
      });
   }
    // Variables declaration - do not modify                     
    private javax.swing.JPanel gamePanel;
    private javax.swing.JTextField txtCount;
    // End of variables declaration                   

   private void moveFood()
   {
      for (int i = 0; i < foodList.size(); i++)
      {
         foodList.get(i).hide();
      }

      for (int i = 0; i < foodList.size(); i++)
      {
         foodList.get(i).move();
      }
      for (int i = 0; i < foodList.size(); i++)
      {
         foodList.get(i).draw();
      }
   }

Answer 1

• You're doing your Swing drawing incorrectly. You should not call getGraphics() on a component and then draw on it since the Graphics object thus obtained won't persist, and neither will your drawing..
• Instead draw in a JComponent's paintComponent(Graphics g) method override.
• You will want to call the super.paintComponent(g); inside the override mentioned above, usually on the first line of your method override. This will erase any old images for you.
• The basic Performing Custom Painting with Swing Tutorial will help you with the details
• And the Painting in AWT and Swing article will tell you more of the advanced information that you'll want to know.