聆聽者和定時器之間的通信

Question

即時通訊相當新的Java和我很困惑如何做到這一點。我有一個聽取WASD的關鍵聽衆，它指示我的Snake的移動。關鍵聽衆改變了我的蛇段的x和y位置。我有一個計時器鏈接到名爲「Listener」的監聽器，該監聽器將移動重新繪製到緩衝區和屏幕上。我的問題是，爲什麼我的關鍵聽衆指示的移動不會將其放到緩衝區中？另外，我知道我的移動功能工作原因是snek.move（4）;在計時器中工作。最後說明，這是一個我幾乎沒有開始的Snake遊戲。

import javax.swing.*; 
import java.awt.*; 
import java.awt.event.*; 
import java.awt.image.*; 
public class SnekePanel extends JPanel 
{ 
    private static final int FRAME1 = 1000; 
    private static final int FRAME2 = 1000; 
    private static final Color BACKGROUND = new Color(0, 0, 0); 
    private BufferedImage myImage; 
    private Graphics myBuffer; 
    private Sneke snek; 
    private Food food; 
    private Timer t; 
    private int points = 0; 
    public SnekePanel() 
    { 
     myImage = new BufferedImage(FRAME1, FRAME2, BufferedImage.TYPE_INT_RGB); 
     myBuffer = myImage.getGraphics(); 
     myBuffer.setColor(BACKGROUND); 
     myBuffer.fillRect(0, 0, FRAME1,FRAME2); 
     int xPos = (int)(Math.random()*(FRAME1-100) + 50); 
     int yPos = (int)(Math.random()*(FRAME2-100)+ 50); 
     food = new Food(xPos, yPos, 10, Color.RED); 
     snek = new Sneke(200,200,1,Color.WHITE); 
     t = new Timer(5, new Listener()); 
     t.start(); 
     addKeyListener(new Key()); 
     setFocusable(true); 
    } 

    public void paintComponent(Graphics g) 
    { 
     g.drawImage(myImage, 0, 0, getWidth(), getHeight(), null); 
    } 

    private class Key extends KeyAdapter 
    { 
     public void keyPressed(KeyEvent e) 
     { 
     if(e.getKeyCode() == KeyEvent.VK_W) 
     { 
      snek.move(1); 
     } 
     if(e.getKeyCode() == KeyEvent.VK_A) 
     { 
      snek.move(2); 
     } 
     if(e.getKeyCode() == KeyEvent.VK_S) 
     { 
      snek.move(3); 
     } 
     if(e.getKeyCode() == KeyEvent.VK_D) 
     { 
      snek.move(4); 
     } 

     } 

    } 

    private class Listener implements ActionListener 
    { 
     public void actionPerformed(ActionEvent e) 
     { 
     if(snek.checkBlock() != 0) 
     { 
      myBuffer.setColor(BACKGROUND); 
      myBuffer.fillRect(0,0,FRAME1,FRAME2); 
      snek.move(4); 
      collide(snek, food); 
      food.draw(myBuffer); 
      snek.draw(myBuffer); 
      myBuffer.setColor(Color.BLACK); 
      repaint(); 
     } 
     } 
    } 

    private void collide(Sneke b, Food pd) 
    { 
     int sx = b.getX(snek.getLength()-1); 
     int sy = b.getY(snek.getLength()-1); 
     int fx = pd.getX(); 
     int fy = pd.getY(); 
     if(sx == sy && fx == fy) 
     { 
     snek.setLength(snek.getLength()+1); 
     } 
    } 
} 

Answer 1

爲什麼我的鑰匙聽衆表示運動沒有使它的緩衝區？

在我心中一個更重要的問題是：爲什麼你認爲它應該它做出緩衝？在調用snek.move(4)之後，您只繪製了緩衝區，所以看起來只有這樣才能進入緩衝區。

我自己，我會做不同的事情，包括（除其他事項外）

• 我會創造一個int領域 - 或者更好的封裝上，下方向枚舉，左，右。
• 我會給我的圖形用戶界面這個上面的領域，我將它設置在KeyListener中。
• 我實際上更喜歡使用鍵綁定而不是KeyListener，因爲它涉及到焦點問題的時候要少得多，但兩者都可以工作。
• 在我的定時器，我會基於價值的在該領域的國家移動精靈

例如，嘗試運行此：

import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.Point; 
import java.awt.RenderingHints; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.awt.event.KeyEvent; 
import java.util.LinkedList; 
import java.util.List; 

import javax.swing.*; 


@SuppressWarnings("serial") 
public class SnakePanel extends JPanel { 
    // size of the GUI 
    private static final int PREF_W = 1000; 
    private static final int PREF_H = 800; 

    // background and snake color 
    private static final Color BG = Color.BLACK; 
    private static final Color SNAKE_COLOR = Color.RED; 
    private static final int SEGMENT_WIDTH = 20; 

    // distance moved in each timer tick, and time between each tick 
    private static final int DELTA = 5; 
    private static final int TIMER_DELAY = 40; // in msecs 

    // number of segments in the worm 
    private static final int WORM_LENGTH = 80; 

    // initial direction 
    private Direction direction = Direction.RIGHT; 

    // initial point 
    private Point point = new Point(PREF_W/2, PREF_H/2); 

    // Snake is little more than a List of Points 
    private List<Point> snakePointList = new LinkedList<>(); 

    public SnakePanel() { 
     // set background color 
     setBackground(BG); 

     // fill snake list with points 
     for (int i = 0; i < WORM_LENGTH; i++) { 
      snakePointList.add(new Point(point)); 
     } 

     // set key bindings 
     setKeyBindings(); 

     // create and start Timer 
     new Timer(TIMER_DELAY, new TimerListener()).start(); 
    } 

    // set up our key bindings 
    private void setKeyBindings() { 
     int condition = WHEN_IN_FOCUSED_WINDOW; 
     InputMap inputMap = getInputMap(condition); 
     ActionMap actionMap = getActionMap(); 

     KeyStroke keyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0); 
     setKeyStroke(inputMap, actionMap, keyStroke, Direction.UP);   
     keyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0); 
     setKeyStroke(inputMap, actionMap, keyStroke, Direction.DOWN); 
     keyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0); 
     setKeyStroke(inputMap, actionMap, keyStroke, Direction.LEFT); 
     keyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0); 
     setKeyStroke(inputMap, actionMap, keyStroke, Direction.RIGHT); 
    } 

    private void setKeyStroke(InputMap inputMap, ActionMap actionMap, KeyStroke keyStroke, 
      Direction dir) { 
     inputMap.put(keyStroke, keyStroke.toString()); 
     actionMap.put(keyStroke.toString(), new MyKeyAction(dir)); 
    } 

    @Override 
    protected void paintComponent(Graphics g) { 
     super.paintComponent(g); 
     Graphics2D g2 = (Graphics2D) g; 
     // smooth out our graphics 
     g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); 

     // draw each oval in the Snake 
     for (Point pt : snakePointList) { 
      drawPoint(g2, pt); 
     } 
    } 

    private void drawPoint(Graphics2D g2, Point pt) { 
     g2.setColor(SNAKE_COLOR); 

     // The pt is actually the center point 
     // so we need to draw an oval that is centered on this point 
     int x = pt.x - SEGMENT_WIDTH/2; 
     int y = pt.y - SEGMENT_WIDTH/2; 
     g2.drawOval(x, y, SEGMENT_WIDTH, SEGMENT_WIDTH); 
    } 

    // set gui's size 
    @Override 
    public Dimension getPreferredSize() { 
     if (isPreferredSizeSet()) { 
      return super.getPreferredSize(); 
     } 
     return new Dimension(PREF_W, PREF_H); 
    } 

    // Action used by key binding 
    private class MyKeyAction extends AbstractAction { 
     private Direction dir; 

     public MyKeyAction(Direction dir) { 
      this.dir = dir; 
     } 

     public void actionPerformed(ActionEvent e) { 
      // all it does is set the Direction direction enum field 
      // for this GUI 
      // the Timer then uses this field 
      SnakePanel.this.direction = dir; 
     }; 
    } 

    // timer ActionListener 
    private class TimerListener implements ActionListener { 
     @Override 
     public void actionPerformed(ActionEvent e) { 
      // create a new Point whose direction depends 
      // on the direction field * multiplier, DELTA 
      int x = point.x + direction.getX() * DELTA; 
      int y = point.y + direction.getY() * DELTA; 

      // create new point and add to snakePointList 
      point = new Point(x, y); 
      snakePointList.add(point); 
      // remove last point in list 
      snakePointList.remove(0); 
      repaint(); 
     } 
    } 

    // Direction enum 
    enum Direction { 
     UP(0, -1), DOWN(0, 1), LEFT(-1, 0), RIGHT(1, 0); 

     private Direction(int x, int y) { 
      this.x = x; 
      this.y = y; 
     } 
     private int x; 
     private int y; 

     public int getX() { 
      return x; 
     } 

     public int getY() { 
      return y; 
     } 
    } 

    private static void createAndShowGui() { 
     SnakePanel mainPanel = new SnakePanel(); 

     JFrame frame = new JFrame("SnakePanel"); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.getContentPane().add(mainPanel); 
     frame.pack(); 
     frame.setLocationRelativeTo(null); 
     frame.setVisible(true); 
    } 

    public static void main(String[] args) { 
     SwingUtilities.invokeLater(() -> createAndShowGui()); 
    } 
}