Android Constraint Layout showing attribute 'android:layout_constraintWidth_percent' not found

Question

I searched a lot for this error but ended up seeing that everyone is suggesting of uninstalling android studio and reinstalling it with all sdk work which is not feasible to me. How can we remove this error in a decent way, please refer me to the answer if anyone has already given the right one.

Answer 1

Please use app instead of android.

app:layout_constraintWidth_percent="0.5"    

Also, Add one constraint property like below:

    app:layout_constraintStart_toStartOf="parent"  

or

app:layout_constraintTop_toTopOf="parent"  

your_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/btn_temp"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:layout_constraintWidth_percent="0.5"
        android:text="Hello World!"
        app:layout_constraintTop_toTopOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>