ConstraintLayout constraints attribute in style

Question

How to use constraint attributes in style?

When I'm trying to use it as any other attributes with custom namespace it's has no effect on my view.

 <style name="Header.Center" parent="Header">
    <item name="layout_constraintBottom_toBottomOf">parent</item>
 </style>

Adding namespace app: is not helping.

Answer 1

First of all, make sure that the View that you're applying the style on is a direct child of the ConstraintLayout. Otherwise, the constraints will not be taken into account when positioning the View.

I have tried it and the way you tried does in fact work. I have added the following style to the styles.xml:

<style name="CustomStyle">
    <item name="layout_constraintBottom_toBottomOf">parent</item>
    <item name="layout_constraintEnd_toEndOf">parent</item>
</style>

Created a basic layout:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:text="Text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        style="@style/CustomStyle"/>

</android.support.constraint.ConstraintLayout>

And it does indeed position the TextView at the bottom right corner of the parent.

Answer 2

maybe your view's attribute is "match_parent",but it is wrong. It should be "wrap_content".

 <TextView
            android:text="Text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            style="@style/CustomStyle"/>