18.12 Adding Guidelines
Guidelines provide additional elements to which constraints may be anchored. Guidelines are added by right-clicking on the layout and selecting either the Add Vertical Guideline or Add Horizontal Guideline menu option or using the toolbar menu options as shown in Figure 18-28:
Figure 18-28
Once added, a guideline will appear as a dashed line in the layout and may be moved simply by clicking and dragging the line. To establish a constraint connection to a guideline, click in the constraint handler of a widget and drag to the guideline before releasing. In Figure 18-29, the left sides of two Buttons are connected by constraints to a vertical guideline.
The position of a vertical guideline can be specified as an absolute distance from either the left or the right of the parent layout (or the top or bottom for a horizontal guideline). The vertical guideline in the above figure, for example, is positioned 96dp from the left-hand edge of the parent.
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