问题:

I've added a KeyListener to a TextArea and wish to check if any key is pressed down. I have the following but it's too clumsy to check for all the letters and numbers:

public void keyPressed(KeyEvent e) {
if(e.getKeyCode() == KeyEvent.VK_A || e.getKeyCode() == KeyEvent.VK_B || 
e.getKeyCode() == KeyEvent.VK_C ||e.getKeyCode() == KeyEvent.VK_D etc...){  

    }   
}

回答1:

You wouldn't need any if statements. The keyPressed method is fired whenever a key is pressed, so you're automatically thrown into the method.

回答2:

I think you can use KeyEvent.getKeyChar() or KeyEvent.getKeyCode() method which will returns character value/code of key pressed.

For alphanumericals A-Z,a-z,0-9;

int key= KeyEvent.getKeyCode();

if((((key>=65)&&(key<=90))||((key>=97)&&(key<=122))||((key>=48)&&(key<=57)))
{
//Do action
}

回答3:

Create a list of respective key events and check if the list contains those events.

List keyEvents = new ArrayList<KeyEvent>();
keyEvents.add(KeyEvent.VK_A);
keyEvents.add(KeyEvent.VK_B);
keyEvents.add(KeyEvent.VK_C);
keyEvents.add(KeyEvent.VK_D);

public void keyPressed(KeyEvent e) {
if(keyEvents.contains(e.getKeyCode())){  

    }   
}