addSizeCallback method
Implementation
void addSizeCallback(int id, String viewType, OnPlatformSizeChangedCallback callback) {
_sizeCallbacks[_widgetKey(id, viewType)] = callback;
}
void addSizeCallback(int id, String viewType, OnPlatformSizeChangedCallback callback) {
_sizeCallbacks[_widgetKey(id, viewType)] = callback;
}