Question

我想禁止我的Sprite对象移动画布的某些坐标。我怎样才能做到这一点？我到目前为止做了什么：

包project1;

import java.awt.*;       
// Using AWT's Graphics and Color 
import java.awt.event.*; 
// Using AWT's event classes and listener
interfaces import javax.swing.*;    
// Using Swing's components and containers 
/**  
* Custom Graphics Example: Using key/button to move a object left or right.
* The moving object (sprite) is defined in its own class, with its own  
* operations and can paint itself.  *  
*/  class Sprite {
// Variables (package access)
public int x;
public int y;
int width, height;
// Use an rectangle for illustration
Color color = Color.RED; // Color of the object
// Constructor
public Sprite(int x, int y, int width, int height, Color color) {
      this.x = x;
      this.y = y;
      this.width = width;
      this.height = height;
      this.color = color;
}
// Paint itself given the Graphics context
public void paint(Graphics g) {
      g.setColor(color);
      g.fillRect(x, y, width, height); // Fill a rectangle
      // g.drawLine(20, 0, 20, 240);
      System.out.println("paint   X: "+x+"  Y: "+y);

      //System.out.println("paint 2nd   X: "+x+"  Y: "+y);    } } 


public class Project1 extends JFrame {
// Define constants for the various dimensions
    public static final int CANVAS_WIDTH = 400;
    public static final int CANVAS_HEIGHT = 240;
    public static final Color CANVAS_BG_COLOR = Color.CYAN;
    private DrawCanvas canvas;
    // the custom drawing canvas (an inner class extends JPanel)
    private  Sprite sprite;     // the moving object
    // Constructor to set up the GUI components and event handlers
    public Project1() {
      // Construct a sprite given x, y, width, height, color
      int x = 0,y = 0;
      sprite = new Sprite(CANVAS_WIDTH / 2 - 30, CANVAS_HEIGHT / 2 - 30,
            10, 10, Color.RED);

      // Set up a panel for the buttons
      JPanel btnPanel = new JPanel(new FlowLayout());
      JButton btnLeft = new JButton("Move Left ");
      btnPanel.add(btnLeft);
      btnLeft.addActionListener(new ActionListener() {
         @Override
         public void actionPerformed(ActionEvent evt) {

            moveLeft();


            requestFocus(); // change the focus to JFrame to receive KeyEvent
         }
      });

       //JPanel btnPanel1 = new JPanel(new FlowLayout());
      JButton btnDown = new JButton("Move down ");
      btnPanel.add(btnDown);
      btnDown.addActionListener(new ActionListener() {
         @Override
         public void actionPerformed(ActionEvent evt) {
            moveDown();
            requestFocus(); // change the focus to JFrame to receive KeyEvent
         }
      });

      JButton btnRight = new JButton("Move Right");
      btnPanel.add(btnRight);
      btnRight.addActionListener(new ActionListener() {
         @Override
         public void actionPerformed(ActionEvent evt) {
            moveRight();
            requestFocus(); // change the focus to JFrame to receive KeyEvent
         }
      });

        JButton btnUp = new JButton("Move Up");
      btnPanel.add(btnUp);
      btnUp.addActionListener(new ActionListener() {
         @Override
         public void actionPerformed(ActionEvent evt) {
            moveUp();
            requestFocus(); // change the focus to JFrame to receive KeyEvent
         }
      });

      // Set up the custom drawing canvas (JPanel)
      canvas = new DrawCanvas();
      canvas.setPreferredSize(new Dimension(CANVAS_WIDTH, CANVAS_HEIGHT));

      // Add both panels to this JFrame
      Container cp = getContentPane();
      cp.setLayout(new BorderLayout());
      cp.add(canvas, BorderLayout.CENTER);
      cp.add(btnPanel, BorderLayout.SOUTH);

      // "super" JFrame fires KeyEvent
      addKeyListener(new KeyAdapter() {
         @Override
         public void keyPressed(KeyEvent evt) {
            switch(evt.getKeyCode()) {
               case KeyEvent.VK_LEFT:  moveLeft();  break;
               case KeyEvent.VK_RIGHT: moveRight(); break;
               case KeyEvent.VK_DOWN: moveDown(); break;
               case KeyEvent.VK_UP: moveUp(); break;
            }
         }
      });

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setTitle("Move a Sprite");
      pack();            // pack all the components in the JFrame
      setVisible(true);  // show it
      requestFocus();    // "super" JFrame requests focus to receive KeyEvent    }
     // Helper method to move the sprite left    private void moveLeft() {
      // Save the current dimensions for repaint to erase the sprite
      int savedX = sprite.x;
      // update sprite
      sprite.x -= 10;
      // Repaint only the affected areas, not the entire JFrame, for efficiency
      canvas.repaint(savedX, sprite.y, sprite.width, sprite.height); // Clear old area to background
      canvas.repaint(sprite.x, sprite.y, sprite.width, sprite.height); // Paint new location    }

    // Helper method to move the sprite right    private void moveRight() {
      // Save the current dimensions for repaint to erase the sprite
      int savedX = sprite.x;
      // update sprite
      sprite.x += 10;
      // Repaint only the affected areas, not the entire JFrame, for efficiency
      canvas.repaint(savedX, sprite.y, sprite.width, sprite.height); // Clear old area to background
      canvas.repaint(sprite.x, sprite.y, sprite.width, sprite.height); // Paint at new location    }
     private void moveDown() {
      //Save the current dimensions for repaint to erase the sprite
      int saved = sprite.y;
      // update sprite
      sprite.y += 10;
      // Repaint only the affected areas, not the entire JFrame, for efficiency
     canvas.repaint( sprite.x, saved, sprite.width, sprite.height); // Clear old area to background
      canvas.repaint(sprite.x, sprite.y, sprite.width, sprite.height); // Paint new location    }   private void moveUp() {
      //Save the current dimensions for repaint to erase the sprite
      int savedY = sprite.y;
      // update sprite
      sprite.y -= 10;
      // Repaint only the affected areas, not the entire JFrame, for efficiency
     canvas.repaint( sprite.y, savedY, sprite.width, sprite.height); // Clear old area to background
      canvas.repaint(sprite.x, sprite.y, sprite.width, sprite.height); // Paint new location    }

     // Define inner class DrawCanvas, which is a JPanel used for custom drawing    class DrawCanvas extends JPanel {
      @Override
      public void paintComponent(Graphics g) {
         super.paintComponent(g);
         setBackground(CANVAS_BG_COLOR);
         sprite.paint(g);  // the sprite paints itself
      }    }
     // The entry main() method    public static void main(String[] args) {
      // Run GUI construction on the Event-Dispatching Thread for thread safety
      SwingUtilities.invokeLater(new Runnable() {
         @Override
         public void run() {
            new Project1(); // Let the constructor do the job
         }
      });
    }


}

Answer 1

代码中的注释太多，难以发现问题，但是，从您的问题出发，您可以使用网格来跟踪x＆amp; y坐标。然后检查对象所在的坐标是否与您不希望对象移动到的位置相对应。我在模拟中使用相同的策略。

如何禁止我的Sprite对象在canvas的某些坐标上移动

1 个答案: