18.4 Guideline Helper
Guidelines are special elements available within the ConstraintLayout that provide an additional target to which constraints may be connected. Multiple guidelines may be added to a ConstraintLayout instance which may, in turn, be configured in horizontal or vertical orientations. Once added, constraint connections may be established from widgets in the layout to the guidelines. This is particularly useful when multiple widgets need to be aligned along an axis. In Figure 18-11, for example, three Button objects contained within a ConstraintLayout are constrained along a vertical guideline:
Figure 18-11
