Adding margin to TextView in Constraint Layout using XML

Question

I want to add left and right margins to TextView Widget but it doesn't seem to be working.

Here's my activity XML:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.sayhi.DisplayOutput"
    tools:layout_editor_absoluteY="81dp">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="140dp"
        android:text="@string/output"
        android:textSize="30sp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>

Here's what it looks like:

I am using GUI layout editor. I tried adding padding to the widget and padding works as expected. I think I am missing something basic about layout but I am not sure what.

I am using Android Studio 2.3, ConstraintLayout 1.0.2, AppCompat v7:26, Build Tools Version 26.0.2.

Answer 1

Change

android:layout_width="wrap_content"

to

android:layout_width="match_parent"
// or 
android:layout_width="0dp"

As TextView 's width .