public void update() {
LayerTreeTreeNode selected = tree.getSelectedLayerTreeNode();
if (selected != null && action.isEnabled(selected.getLayer())) {
setDisabled(false);
setIcon(action.getIcon());
setTooltip(action.getTooltip());
} else {
setDisabled(true);
setIcon(action.getDisabledIcon());
setTooltip("");
}
}