Why does the Cannot read property 'checked' of null error occur?

Question

Android

The code

Answer 1

I suppose

androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'

Added studio, remove them.
or raise implementation version 'com.android.support:appcompat-v7:26.1.0'

Answer 2

Well, for decency in the cycle, look what you get. Writes that null does not have such a property - this means that you have a .checked variable
somewhere . And the variable is null . And where do you have arrRefs updated with data? You only declared it in the constructor and that's it.