Robot class - If a Button Is Pressed?

Question

I have read and understood how the Robot class in java works. Only thing I would like to ask, is how do I press and release the mouse button inside an if statement. For example I would to make a click only if (and right after) the space button is pressed/released. I would use the code:

try {
  Robot robot = new Robot();
  if (/*insert my statement here*/) {
    try {
      robot.mousePress(InputEvent.BUTTON1_MASK);
      robot.mouseRelease(InputEvent.BUTTON1_MASK);
    } catch (InterruptedException ex) {}
  }
} catch (AWTException e) {}

Answer 1

Unfortunately, there isn't a way to directly control hardware (well, in fact there is, but you would have to use JNI/JNA), this means that you can't simply check if a key is pressed.

You can use KeyBindings to bind the space key to an action, when the spacebar is pressed you set a flag to true, when it's released you set that flag to false. In order to use this solution, your application has to be a GUI application, this won't work with console applications.

Action pressedAction = new AbstractAction() {
    public void actionPerformed(ActionEvent e) {
        spaceBarPressed = true;
    }
};

Action releasedAction = new AbstractAction() {
    public void actionPerformed(ActionEvent e) {
        spaceBarPressed = false;
    }
};

oneOfYourComponents.getInputMap().put(KeyStroke.getKeyStroke("SPACE"), "pressed");
oneOfYourComponents.getInputMap().put(KeyStroke.getKeyStroke("released SPACE"), "released");
oneOfYourComponents.getActionMap().put("pressed", pressedAction);
oneOfYourComponents.getActionMap().put("released", releasedAction);

Then, use

try {
    Robot robot = new Robot();
    if (spaceBarPressed) {
        try {
            robot.mousePress(InputEvent.BUTTON1_MASK);
            robot.mouseRelease(InputEvent.BUTTON1_MASK);
        } catch (InterruptedException ex) {
            //handle the exception here
        }
    }
} catch (AWTException e) {
    //handle the exception here
}

As GGrec wrote, a better way to do it would be to execute your mouse press directly when the keyboard event is fired:

Action pressedAction = new AbstractAction() {
    public void actionPerformed(ActionEvent e) {
        try {
            robot.mousePress(InputEvent.BUTTON1_MASK);
            robot.mouseRelease(InputEvent.BUTTON1_MASK);
        } catch (InterruptedException ex) {
            //handle the exception here
        }
    }
};