After having activated for the first time the swiping layer/group then is not possible to change it. Clicking the plugin button has no effect. Starting a new project too. The only solution is to close and reopen qgis.
Has a bug in some OS, i use the Kubuntu 14.04, for change the active layer, change the map tool(ex. Pan) and back to Swipe tool.
Sorry for this inconvenient.
After having activated for the first time the swiping layer/group then is not possible to change it. Clicking the plugin button has no effect. Starting a new project too. The only solution is to close and reopen qgis.