KeyListener, keyPressed versus keyTyped

问题

I have a JFrame (well, a class which extends JFrame) and I want to do an action when I press the F5 key. So, I made the class implement KeyListener. And with that, came three methods, keyPressed, keyReleased, and keyTyped.

Which of these methods should I use to listen for F5 being pressed? keyPressed or keyTyped? I currently have the following, however it does not print anything when I press F5.

public void keyPressed(KeyEvent e) {
    if(e.getKeyCode() == KeyEvent.VK_F5)
        System.out.println(\"F5 pressed\");
}

public void keyReleased(KeyEvent arg0) {
    // TODO Auto-generated method stub

}

public void keyTyped(KeyEvent arg0) {
    // TODO Auto-generated method stub

}

回答1:

keyPressed - when the key goes down
keyReleased - when the key comes up
keyTyped - when the unicode character represented by this key is sent by the keyboard to system input.

I personally would use keyReleased for this. It will fire only when they lift their finger up.

Note that keyTyped will only work for something that can be printed (I don't know if F5 can or not) and I believe will fire over and over again if the key is held down. This would be useful for something like... moving a character across the screen or something.

回答2:

Neither. You should NOT use a KeyLIstener.

Swing was designed to be used with Key Bindings. Read the section from the Swing tutorial on How to Use Key Bindings.

回答3:

You should use keyPressed if you want an immediate effect, and keyReleased if you want the effect after you release the key. You cannot use keyTyped because F5 is not a character. keyTyped is activated only when an character is pressed.

回答4:

private String message;
private ScreenManager s;


//Here is an example of code to add the keyListener() as suggested; modify 
public void init(){
Window w = s.getFullScreenWindow();
w.addKeyListener(this);

public void keyPressed(KeyEvent e){
    int keyCode = e.getKeyCode();
        if(keyCode == KeyEvent.VK_F5)
            message = "Pressed: " + KeyEvent.getKeyText(keyCode);
}

来源：https://stackoverflow.com/questions/7071757/keylistener-keypressed-versus-keytyped

标签

java

swing

jframe

key-bindings

keylistener