Java KeyAdapter

Question

我对Java KeyAdapter的工作方式有点不熟悉，并且使用KeyAdapter使用以下代码获得意外结果。无论是否调用isKeyPressed()，当按下某个键而另一个键已被按下时，会出现问题。

注意：我知道这是很多代码，我道歉。我尽我所能来隔离它，我认为它主要围绕下面keyHandler方法中的注释（keyHandler()如何将当前按下的键放入keysHeld）。希望彻底的评论很有帮助。

keyHandler：

ArrayList keysHeld = new ArrayList<KeyEvent>();

private void keyHandler()
{
    KeyAdapter keyListnr = new KeyAdapter()
    {
        public void keyPressed(KeyEvent e)
        { 
            int keyCode = e.getKeyCode();

            int index = 0;
            boolean found = false;
            while(!found && index<keysHeld.size()) //While not already found, and end of ArrayList not reached
            {
                System.out.print("errorCheck: keysHeld: "+keysHeld+", "+(Object)keyCode+" "); //PRINT
                if(keysHeld.get(index) == (Object)keyCode)
                {
                    System.out.println("found"); //PRINT
                    found = true; //This key is already recognized as held
                }
                else
                {
                    System.out.println("not found"); //PRINT
                    //This key is not recognized as held
                }
            }
            if(!found) //If key must be added to keysHeld
            {
                keysHeld.add(keyCode); //Add to list of held keys
            }
        System.out.println(keysHeld.toString()); //PRINT ArrayList of all held keys
    } //end of keyPressed


        public void keyReleased(KeyEvent e) //similar in concept to keyPressed
        {
         int keyCode = e.getKeyCode();

         int index = 0;
         boolean found = false;
         while(!found && index < keysHeld.size())
         {
          if(keysHeld.get(index) == (Object)keyCode)
          {
           keysHeld.remove(index); //remove key from keysHeld
           found = true;
          }
          else
          {
           index++;
          }
         }
         System.out.println(keysHeld.toString()); //PRINT ArrayList of all held keys
        } //end of keyReleased
    };
    addKeyListener( keyListnr );
}

isKeyHeld：

public boolean isKeyHeld(int e)
{
 int keyCode = e;
 Object key = (Object)keyCode;

 if(!keysHeld.isEmpty())
 {
  int index = 0;
  while(index<keysHeld.size())
  {
   if(keysHeld.get(index) == key)
   {
    return true;
   }
   index++;
  }
 }
 return false;
}

控制台输出:(持有leftArrow [37]，然后按下rightArrow [39]）

[37]
errorCheck: keysHeld: [37], 39 not found
errorCheck: keysHeld: [37], 39 not found
errorCheck: keysHeld: [37], 39 not found
errorCheck: keysHeld: [37], 39 not found
...

Answer 1

几点：

• 您不是使用keysHeld的实例填充KeyEvent数组，而是使用从Integer keyCodes派生的autoBoxed int对象填充。
• 如果您希望退出index
中的while循环，则需要增加keyPressed变量
• 您不应该使用==来比较Objects循环中的两个while

您可以使用以下内容进行测试：

    if(keysHeld.get(index++).equals(new Integer(keyCode))

Answer 2

处理多个密钥时，最好使用keyReleased(KeyEvent)方法：它可以在密钥发布期间更轻松地处理多个密钥组合。

我注意到的是，当在keyPressed()内时，我只会捕获一个关键字符。在keyReleased上，我能够捕获多个字符（例如 CTRL - V ）。