Listeners get deleted when you add new ones

[marcglasberg]

There is a bug here:

  /// Subscribe to a keyboard event.
  /// [listener] object to listen the event.
  /// Returns a subscribing id that can be used to unsubscribe.
  int add({required KeyboardListener listener}) {
    final int length = _listenersKeyboardEvents.length;
    _listenersKeyboardEvents[length] = listener;
    return length;
  }

If you add one listener listener1 (length is 0, becomes 1):

{0: listener1}

Then add a second listener listener2 (length is 1, becomes 2):

{0: listener1, 1: listener2}

Then remove the one with id 0 (length is 2, becomes 1):

{1: listener2}

But now if you add a third listener listener3, since length is now 1, it will overwrite listener2, and you'd get:

{1: listener3}

The solution is creating an independent counter that never repeats:

static int _count = 0;

  /// Subscribe to a keyboard event.
  /// [listener] object to listen the event.
  /// Returns a subscribing id that can be used to unsubscribe.
  int add({required KeyboardListener listener}) {
    _listenersKeyboardEvents[_count] = listener;
    _count++;
    return _count;
  }