Children, Respect Your Parent(s)

I was updating a bit of code the other day that involved dynamically inflating views into a LinearLayout using DataBindingUtil.inflate(LayoutInflater.from(context), R.layout.row_related_property, container, false).

I decided to jump in and update it to use the generated binding’s inflate method: RowRelatedPropertyBinding.inflate(LayoutInflater.from(context)) instead.

This inflated layout has margins set on it’s root, similar to this:

<LinearLayout
        android:orientation="vertical"
        android:layout_marginTop="16dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <!-- more views here -->
</LinearLayout>

Happy with my changes, I ran the app and immediately noticed a problem. All the views are smooshed together! Show layout bounds tell me that there is no margin being set at all.

My first thought was that generated binding inflation behaves differently. Odd. I looked through the code and it seems to call through to the same method. Weird.

With a little help from my friends (holla Hugo!), I was quickly pointed out the error of my ways. It is important to respect your parent(s)! And by respect I mean pass it on into inflate.

RowRelatedPropertyBinding.inflate(LayoutInflater.from(context), container, false);

One thing I always forget is that any layout_* attribute is an instruction to the parent. Whenever I am reminded of this, I always go “Ah yes of course I knew that”.

The code that generated the screenshot above is in my Sandbox repo.

If you want to read more about views, layouts, and attributes, go ahead and read Ian Lake’s excellent Medium post on the topic.

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