CODEWITHSUNDEEP
javaswingfocuskeylistener
user2379129
user2379129

Reputation: 11

KeyListener wont focus

I'm new to Java so please forgive me asking for help, but after 4 hours of searching for a solution I'm really getting desperate.

I'm currently setting up a game and want to implement key controls. I tried to do this via KeyListener and KeyEventDispatcher but I just can't get it to work. The KeyListener just won't react. I think that the method that is supposed to use it has the focus.

Here's the code:

public class Sins extends JFrame implements KeyEventDispatcher  {

 public boolean dispatchKeyEvent(KeyEvent e) {
     if (e.getID() == KeyEvent.KEY_PRESSED ) {
         if(KeyEvent.VK_UP == e.getID()){
             System.exit(0); 
         }

     } else if (e.getID() == KeyEvent.KEY_RELEASED) {
           if(KeyEvent.VK_UP == e.getID()){
             System.exit(0); 
           }
     } else if (e.getID() == KeyEvent.KEY_TYPED) {
           if(KeyEvent.VK_UP == e.getID()){
             System.exit(0); 
           }
     }
     return false;
 }

and here is the method where it is supposed to be working at:

  public void run() { 

  setFocusable(true);   
  backgroundGraphics = (Graphics2D) background.getGraphics();
  long fpsWait = (long) (1.0 / 30 * 1000);



requestFocusInWindow();

main: while (isRunning==true) {
    long renderStart = System.nanoTime();

    KeyboardFocusManager manager = KeyboardFocusManager.getCurrentKeyboardFocusManager();
    manager.addKeyEventDispatcher(this);

    x++;
    requestFocusInWindow();

    // Update Graphics
    do {
        Graphics2D bg = getBuffer();

        if (isRunning == false) {
            break main;
        }
        renderGame(backgroundGraphics); // this calls your draw method

        if (scale != 1) {
            bg.drawImage(background, 0, 0, width * scale, height
                    * scale, 0, 0, width, height, null);
        } else {
            bg.drawImage(background, 0, 0, null);
        }
        bg.dispose();

        requestFocusInWindow();


        this.requestFocus();

        if(x ==5000){
            isRunning=false;
        }

    } while (!updateScreen());

    // Better do some FPS limiting here
    long renderTime = (System.nanoTime() - renderStart) / 10000;
    try {
        Thread.sleep(Math.max(0, fpsWait - renderTime));
    } catch (InterruptedException e) {
        Thread.interrupted();
        break;
    }


    renderTime = (System.nanoTime() - renderStart) / 10000;

   }

   this.dispose();
   System.exit(0);
}

The program is currently closing itself after counting up to 5000. For test purposes I'm trying to close it via the up button but it just won't close that way. I would really appreciate some help, as I said I'm new to Java.

Upvotes: 1

Views: 352

Answers (1)

MadProgrammer
MadProgrammer

Reputation: 347332

The first problem you were facing with KeyListener is a well know and well documented (here on SO especially). KeyListener will only on respond if the component they are attached to is focusable and has keyboard focus. Think of a text field, when it doesn't have focus, it won't update.

Your second problem is using the KeyBoardFocusManager, which is simply overkill for this problem.

Instead, you should make use of the [Key Bindings] API, which is simpler the having to monitor the KeyBoardFocusManager and more robust then KeyListeners

Upvotes: 1

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