Android custom attributes return null

I'm trying to learn how to use custom attributes in Android Studio. I follow a couple of tutorials on the subject and despite my efforts nothing seems to work. I created a code that illustrates the problem.

I've created simple custom view, which doesnt represent anything but only obtains styled attributes. This is my customView code:

package com.example.mytestattributes;

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.util.Log;
import android.util.TypedValue;
import android.view.View;

import androidx.annotation.Nullable;

public class customView extends View {
    public customView(Context context) {
        super(context);
        init(null);
    }

    public customView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init(attrs);
    }
    private void init(@Nullable AttributeSet attrs){
        if(attrs!=null){
            Log.d("INIT", "attribute set found");
            TypedArray ta = getContext().obtainStyledAttributes(R.styleable.customView);
            Log.d("LENGHT OF TA: ", ta.length()+"");
            Log.d("testString has value", ta.hasValue(R.styleable.customView_testString)+"");
            Log.d("testInteger has value", ta.hasValue(R.styleable.customView_testInteger)+"");
            Log.d("testBoolean has value", ta.hasValue(R.styleable.customView_testBoolean)+"");
            Log.d("testColor has value", ta.hasValue(R.styleable.customView_testColor)+"");
            Log.d("testDimension has value", ta.hasValue(R.styleable.customView_testDimension)+"");
            Log.d("testEnum has value", ta.hasValue(R.styleable.customView_testEnum)+"");

            Log.d("Return testDimension: ", ""+ta.getDimensionPixelSize(R.styleable.customView_testDimension,0));
            Log.d("Return testDimension: ", ""+ta.getDimension(R.styleable.customView_testDimension,0));

        }else{
            Log.d("INIT", "no attribute set found");
        }


    }
}

The code compiles and the output is:

D/INIT: attribute set found
D/LENGHT OF TA:: 6
D/testString has value: false
D/testInteger has value: false
D/testBoolean has value: false
D/testColor has value: false
D/testDimension has value: false
D/testEnum has value: false
D/Return testDimension:: 0
D/Return testDimension:: 0.0

The lenght of typed array is correct, meaning that the program sees the attributes but when I ask it to check if the attributes have value the outcome is false. As a consequence any attempt to read this attibutes always returns default value. In the example code I included just getDimension but the same holds for all other get methods.

This is my attrs.xml, where I defined the attibutes:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="customView">
        <attr name="testString" format="string|reference"/>
        <attr name="testInteger" format="integer"/>
        <attr name="testBoolean" format="boolean"/>
        <attr name="testColor" format="color|reference"/>
        <attr name="testDimension" format="dimension"/>
        <attr name="testEnum" format="enum">
            <enum name="var1" value="1"/>
            <enum name="var2" value="2"/>
        </attr>
    </declare-styleable>
</resources>

I try to pass values in Activity_Main.xml:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity">

    <com.example.mytestattributes.customView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:testBoolean="true"
        app:testDimension="200dp"
        app:testColor="@color/colorAccent"
        app:testEnum="var1"
        app:testInteger="15"
        app:testString="@string/app_name"
        />

</androidx.constraintlayout.widget.ConstraintLayout>

The MainActivity.java is unmodified empty activity class. I am aware that some people had the similiar problems a couple of years ago but no valid answers were ever posted. Is anyone aware what is wrong with this code? Im using API 17.