void shiftPriorityUp(bool flag)
This method moves the layer's display priority up one step if flag is TRUE, and down one step if flag is FALSE. A layer's display priority determines when its contents are drawn in the view, relative to other layers. The layer with the highest priority is drawn first, followed by the layer with the second-highest priority, etc.
The effect of this method is not immediate, i.e. the change in priority is not applied to the view. To apply the change, call MapAPI.applyLayerChanges. Thus, the priority of one layer can be shifted multiple times or multiple layers can be shifted efficiently, i.e. without immediate redraw.