swing - Java Keybinding Plus Key

Question

I was trying to create shortcuts for zooming in and out in an image editing application I'm creating and I noticed something strange. To bind the combination of ctrl + +, I had to use the = key and a control and shift mask:

getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_EQUALS, KeyEvent.CTRL_DOWN_MASK + KeyEvent.SHIFT_DOWN_MASK),"ZoomIn");

Neither of the combinations where I tried to directly bind to VK_PLUS worked:

getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_PLUS, KeyEvent.CTRL_DOWN_MASK + KeyEvent.SHIFT_DOWN_MASK),"ZoomIn");

getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_PLUS, KeyEvent.CTRL_DOWN_MASK),"ZoomIn");

It works right now with the very first line of code, but I was wondering why neither of the bottom two work and if this could (theoretically) be a problem if a keyboard did not have the + key as the shifted = key.

Answer 1

For numeric keypad plus try KeyEvent.VK_ADD:

getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_ADD,
                KeyEvent.CTRL_DOWN_MASK), "plus");

For plus on main keyboard (US keyboard layout) use:

getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_EQUALS, KeyEvent.CTRL_DOWN_MASK | KeyEvent.SHIFT_DOWN_MASK),"plus"); 

For non US keyboard use VK_PLUS. See bugs 4262044 and 6942481 for some clarifications.