使用小键盘在java中移动一个圆圈

Question

因此，我有一个应用程序，根据按下哪个按键的按钮，成功地将球（椭圆）向左，向右，向上或向下移动。但是，我无法让球以一定角度移动。我试图通过说，如果用户持有2个方向键，球将对角线走。例如，如果他们点击左键和上键，我想让球沿着西北方向移动。如果你们中的任何人看到了什么是造成这个问题，我真的很感谢帮助！

引擎

class KeyClickListener implements KeyListener 
     { 
     public void keyPressed(KeyEvent e) 
     { 
      if (e.getKeyCode() == KeyEvent.VK_DOWN) 
       { 
        component.moveCircle(1); 
       } 
      else if (e.getKeyCode() == KeyEvent.VK_UP) 
       { 
        component.moveCircle(2); 
       } 
      else if (e.getKeyCode() == KeyEvent.VK_RIGHT) 
       { 
        component.moveCircle(3); 
       } 
      else if (e.getKeyCode() == KeyEvent.VK_LEFT) 
       { 
        component.moveCircle(5); 
       } 
      //this is my attempt at telling whether or not the user was holding two keys 
      else if (e.getKeyCode() == KeyEvent.VK_LEFT && e.getKeyCode() == KeyEvent.VK_UP) 
       { 
        component.moveCircle(5); 
       } 
     } 
     public void keyReleased(KeyEvent e){} 
     public void keyTyped(KeyEvent e){} 
    } 

CircleComponent

public void moveCircle(int w) 
{ 
    dir = w; 
    if (dir == 1) 
     { 
      y+=20; 
      repaint(); 
      if (y>=560) 
       { 
        dir=2; 
       } 
     } 
. 
. 
. 

else if (dir == 5) 
     { 
      x-=10; 
      y-=10; 
      repaint(); 
      if(x<=0) 
       { 
        dir=3; 
       } 
     } 
} 

Answer 1

因为关键事件将只报告触发事件的最后一个键，你最后if声明不会有任何效果，因为keyCode只会等于触发事件的最后一个键。

相反，您应该保持每个密钥和进程的“状态”，而不是该状态。

import java.awt.BorderLayout; 
import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.EventQueue; 
import java.awt.FontMetrics; 
import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.event.KeyAdapter; 
import java.awt.event.KeyEvent; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.UIManager; 
import javax.swing.UnsupportedLookAndFeelException; 

public class TestKeyListener01 { 

    public static void main(String[] args) { 
     new TestKeyListener01(); 
    } 

    public TestKeyListener01() { 
     EventQueue.invokeLater(new Runnable() { 
      @Override 
      public void run() { 
       try { 
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); 
       } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) { 
       } 

       JFrame frame = new JFrame("Testing"); 
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
       frame.setLayout(new BorderLayout()); 
       frame.add(new TestPane()); 
       frame.pack(); 
       frame.setLocationRelativeTo(null); 
       frame.setVisible(true); 
      } 
     }); 
    } 

    public class TestPane extends JPanel { 

     private boolean arrowUp = false; 
     private boolean arrowDown = false; 
     private boolean arrowLeft = false; 
     private boolean arrowRight = false; 

     public TestPane() { 
      setFocusable(true); 
      addKeyListener(new KeyAdapter() { 

       @Override 
       public void keyReleased(KeyEvent e) { 
        switch (e.getKeyCode()) { 
         case KeyEvent.VK_DOWN: 
          arrowDown = false; 
          break; 
         case KeyEvent.VK_UP: 
          arrowUp = false; 
          break; 
         case KeyEvent.VK_LEFT: 
          arrowLeft = false; 
          break; 
         case KeyEvent.VK_RIGHT: 
          arrowRight = false; 
          break; 
        } 
        repaint(); 
       } 

       @Override 
       public void keyPressed(KeyEvent e) { 
        switch (e.getKeyCode()) { 
         case KeyEvent.VK_DOWN: 
          arrowDown = true; 
          break; 
         case KeyEvent.VK_UP: 
          arrowUp = true; 
          break; 
         case KeyEvent.VK_LEFT: 
          arrowLeft = true; 
          break; 
         case KeyEvent.VK_RIGHT: 
          arrowRight = true; 
          break; 
        } 
        repaint(); 
       } 
      }); 
     } 

     @Override 
     public Dimension getPreferredSize() { 
      return new Dimension(200, 200); 
     } 

     @Override 
     protected void paintComponent(Graphics g) { 
      super.paintComponent(g); 
      Graphics2D g2d = (Graphics2D) g.create(); 
      FontMetrics fm = g2d.getFontMetrics(); 
      String text = "Up"; 
      int x = (getWidth() - fm.stringWidth(text))/2; 
      int y = ((getHeight()/2) - fm.getHeight()); 
      draw(g2d, text, x, y, arrowUp); 

      text = "Down"; 
      x = (getWidth() - fm.stringWidth(text))/2; 
      y = ((getHeight()/2) + fm.getHeight()) + fm.getAscent(); 
      draw(g2d, text, x, y, arrowDown); 

      text = "Left"; 
      x = (getWidth()/2) - fm.stringWidth(text) - 4; 
      y = ((getHeight() - fm.getHeight())/2) + fm.getAscent(); 
      draw(g2d, text, x, y, arrowLeft); 

      text = "Right"; 
      x = (getWidth()/2) + 4; 
      y = ((getHeight() - fm.getHeight())/2) + fm.getAscent(); 
      draw(g2d, text, x, y, arrowRight); 

      g2d.dispose(); 
     } 

     protected void draw(Graphics2D g2d, String text, int x, int y, boolean pressed) { 
      g2d.setColor(pressed ? Color.BLACK : Color.GRAY); 
      g2d.drawString(text, x, y); 
     } 
    } 
} 

我也建议，而不是KeyListener，你应该使用Key Bindings代替。他们解决烦人的焦点问题KeyListener

Answer 2

将您的KeyClickListener更改为并观察魔术！然后结帐这http://zetcode.com/tutorials/javagamestutorial/movingsprites/

class KeyClickListener implements KeyListener, Runnable 
    { 
     private boolean moveLeft, moveRight, moveUp, moveDown; 
     private Thread runThread; 
     public KeyClickListener() { 
      moveLeft = moveRight = moveUp = moveDown = false; 
      runThread = new Thread(this); 
      runThread.start(); 
     } 
     public void keyPressed(KeyEvent e) {assessKeycodes(e, true);} 
     public void keyReleased(KeyEvent e){assessKeycodes(e, false);} 
     public void keyTyped(KeyEvent e){} 

     private void assessKeycodes(KeyEvent e, boolean setTo) { 
      switch(e.getKeyCode()) { 
       case KeyEvent.VK_DOWN: 
        moveDown = setTo; 
        break; 
       case KeyEvent.VK_UP: 
        moveDown = setTo; 
        break; 
       case KeyEvent.VK_LEFT: 
        moveDown = setTo; 
        break; 
       case KeyEvent.VK_RIGHT: 
        moveDown = setTo; 
        break; 
      } 
     } 

     public void run() { 
      while(true) { 
       if (moveDown) 
         component.moveCircle(1); 
       if (moveUp) 
         component.moveCircle(2); 
       if (moveRight) 
         component.moveCircle(3); 
       if (moveLeft) 
         component.moveCircle(5); 
      } 
     } 
    }