Unresolved reference error when using viewLifecycleOwner

Question

I am having an error using Observer and viewLifecycleOwner in my android project. It throws a "Unresolved reference: viewLifecycleOwner" error and I have no clue why. I verified I had the imports

import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProvider

And the dependency:

implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0'

I have tried to Invalidate Caches / Restart... solution found in GitHub. But the error persists. Thanks to anyone who can help me.

class MainActivity : AppCompatActivity() {
    private lateinit var viewModel: DrinkViewModel

    // Contains all the views
    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        viewModel = ViewModelProvider(this).get(MyViewModel::class.java)

        // Use Data Binding to get reference to the views
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main)

        binding.drinkButton.setOnClickListener {
            onDrinkClicked()
        }

        viewModel.revenue.observe(viewLifecycleOwner, Observer { newRevenue ->
            binding.revenueText.text = newRevenue.toString()
        })

        viewModel.drinksSold.observe(viewLifecycleOwner, Observer { newAmount ->
            binding.amountSoldText.text = newAmount.toString()
        })
        binding.drinkButton.setImageResource(viewModel.currentDrink.value!!.imageId)
    }
}

Answer 1

getViewLifecycleOwner() is method to represent fragment's lifeCycle. You can't call it from activiy scope. You can just use this or if you are familiar with coroutines, you can use lifeCycleScope .