What is difference between Barrier and Guideline in Constraint Layout?

Question

Recently trying to implement Constraint Layout but I found Barrier and Guideline works same. Both works like divider.

Answer 1

When to use barriers

Assume you have two TextView widgets with dynamic heights and you want to place a Button just below the tallest TextView:

The ONLY way to implement that directly in the layout is to use a horizontal Barrier. That Barrier allows you to specify a constraint based on the height of those two TextViews. Then you constrain the top of your Button to the bottom of the horizontal Barrier.

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When to use guidelines

Assume you want to restrict the above-mentioned TextView heights to 30% of screen height, no matter the content they have.

To implement that you should add horizontal Guideline with percentage position and constrain the TextView bottom to that Guideline.

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Conclusion

The only difference between Barrier and Guideline is that Barrier's position is flexible and always based on the size of multiple UI elements contained within it and Guideline's position is always fixed.