Barrier

public class Barrier
extends View

Added in 1.1

A Barrier references multiple widgets as input, and creates a virtual guideline based on the most extreme widget on the specified side. For example, a left barrier will align to the left of all the referenced views.

Example

 <android.support.constraint.Barrier android:id="@+id/barrier" android:layout_width="wrap_content" android:layout_height="wrap_content" app:barrierDirection="start" app:constraint_referenced_ids="button1,button2" />  

With the barrier direction set to start, we will have the following result:

Reversely, with the direction set to end, we will have:

If the widgets dimensions change, the barrier will automatically move according to its direction to get the most extreme widget:

Other widgets can then be constrained to the barrier itself, instead of the individual widget. This allows a layout to automatically adapt on widget dimension changes (e.g. different languages will end up with different length for similar worlds).

GONE widgets handling

If the barrier references GONE widgets, the default behavior is to create a barrier on the resolved position of the GONE widget. If you do not want to have the barrier take GONE widgets into account, you can change this by setting the attribute barrierAllowsGoneWidgets to false (default being true).

Summary

Fields

 public static final int BOTTOM

 public static final int END

 public static final int LEFT

 public static final int RIGHT

 public static final int START

 public static final int TOP

Public constructors

 public Barrier (Context context)

 public Barrier (Context context, AttributeSet attrs)

 public Barrier (Context context, AttributeSet attrs, int defStyleAttr)

Public methods

 public boolean allowsGoneWidget ()

 public int getMargin ()

 public int[] getReferencedIds ()

 public int getType ()

 public void loadParameters (ConstraintSet.Constraint constraint, HelperWidget child, ConstraintLayout.LayoutParams layoutParams,  mapIdToWidget)

 public void resolveRtl (ConstraintWidget widget, boolean isRtl)

 public void setAllowsGoneWidget (boolean supportGone)

 public void setDpMargin (int margin)

 public void setMargin (int margin)

 public void setReferencedIds (int[] ids)

 public void setType (int type)

 public void updatePostConstraints (ConstraintLayout constainer)

 public void updatePreLayout (ConstraintWidgetContainer container, Helper helper,  map)

Protected methods

 protected View[] getViews (ConstraintLayout layout)