Java KeyListener.keyPressed多次按住按鍵

Question

當使用keyListeners時，如何使它的計數值僅在用戶按下左鍵時增加1，而不是基於多長時間增加拿住？

public void keyPressed (KeyEvent e){ 
     int keyCode = e.getKeyCode(); 
     if (keyCode == KeyEvent.VK_LEFT){ 
      keyLabel.setText("left"); 
      count++;} 

Answer 1

考慮一個KeyListener，將計算的VK_LEFT每按一次的這個例子 - 即使鍵被按下和射擊多次。

label.addKeyListener(new KeyAdapter() { 

     boolean pressed = false; 
     @Override 
     public void keyPressed (KeyEvent e){ 
      int keyCode = e.getKeyCode(); 
      if (keyCode == KeyEvent.VK_LEFT && !pressed){ 
       pressed = true; 
       keyLabel.setText("left"); 
       System.out.println("Pressed: " + (++count)); 
      } 
     } 
     @Override 
     public void keyReleased (KeyEvent e){ 
      int keyCode = e.getKeyCode(); 
      if (keyCode == KeyEvent.VK_LEFT){ 
       pressed = false; 
       System.out.println("Released."); 
      } 
     }     
    }); 

雖然看起來的keyPressed鍵的同時按下反覆調用，一旦密鑰被釋放的keyReleased僅觸發，所以我們那個時候觸發一個布爾開關pressed。