Determine whether a key is up or down

Determines whether a key is up or down at the time the function is called

Determines whether a key is up or down at the time the function is called, and whether the key was pressed after a previous call to GetAsyncKeyState.
So you don't need to use maltlab 'WindowButtonDownFcn' or 'java KeyPressedCallback'
VirtualKeyCode is an enumeration class for all the different keys and buttons.
See the following link for further information: https://msdn.microsoft.com/de-de/library/windows/desktop/dd375731(v=vs.85).aspx

Examples:

check mouse buttons:
mouseL = getAsyncKeyState(VirtualKeyCode.VK_LBUTTON);
mouseM = getAsyncKeyState(VirtualKeyCode.VK_MBUTTON);
mouseR = getAsyncKeyState(VirtualKeyCode.VK_RBUTTON);

check modifiers:
control = getAsyncKeyState(VirtualKeyCode.VK_CONTROL);
alt = getAsyncKeyState(VirtualKeyCode.VK_MENU);

Inspired by "ismousedpressed" [ https://de.mathworks.com/matlabcentral/fileexchange/61976-check-if-mouse-button-is-pressed?focused=7350547&tab=function ]