CODEWITHSUNDEEP
javaswingkeylistenerctrl
radlan
radlan

Reputation: 2563

KeyListener on JComponent for Ctrl key

I'd like to have a KeyListener on a JComponent in Swing that reacts on press and release of the ctrl key. This a naive, but suboptimal solution (it reacts on every keypress, not only on press/release of the ctrl key:

new KeyAdapater() {
  public void keyPressed(KeyEvent e) {
    if (e.isControlDown()) {
       //do something
    }
  }
  public void keyReleased(KeyEvent e) {
    if (!e.isControlDown()) {
       //do something other
    }
  }
}

What is a better approach to only trigger, when the ctrl key itself is pressed or released?

Upvotes: 0

Views: 3171

Answers (2)

dic19
dic19

Reputation: 17971

IMHO using Key bindings is a more flexible and reliable approach that brings with these benefits:

Having said that, we can create KeyStrokes like follows:

KeyStroke controlKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_CONTROL, 0);

And we can even specify that the key stroke will be triggered on a key release event:

KeyStroke controlReleasedKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_CONTROL, 0, true);

Note: 0 means no modifiers and true is a flag indicating the key stroke represents a key release event. See the API for more details.

See also this topic: Key bindings vs. key listeners in Java, and How to Use Key Bindings tutorial

Upvotes: 4

Paco Abato
Paco Abato

Reputation: 4065

Try this:

public void keyPressed(KeyEvent e) {
    if (e.getKeyCode() == KeyEvent.VK_CONTROL) {
       //do something
    }
}

Upvotes: 3

Related Questions