使用键盘在java中以角度移动圆圈

所以我有一个应用程序可以成功地向左，向右，向上或向下移动一个球（椭圆），具体取决于按下键盘的哪个按钮。 但是，我无法让球以一定角度移动。 我试图这样说，如果用户握住2个方向键，球将对角线。 例如，如果他们单击左键和向上键，我希望球在NorthWest方向上移动。 如果你们中的任何人看到导致问题的原因，我真的很感激帮助！

发动机

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

因为键事件只会报告触发事件的最后一个键，所以最后一个if语句将永远不会起作用，因为keyCode只会等于触发事件的最后一个键。

相反，您应该维护每个键的“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); } } } 

我还建议您使用Key Binding而不是KeyListener 。 它们解决了困扰KeyListener烦人焦点问题

Answer 2

将KeyClickListener更改为并观察魔法！ 然后结帐这个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); } } }