The same issue occurred my code base too. The kotlin version is '1.4.32'

After removing below import sentiment, the warning disappeared.

import androidx.lifecycle.observe

In my case I used Kotlin 1.4.31 in buildgradle(project level) file.

 ext {
    kotlin_version = '1.4.31'
}

 dependencies {
 classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
}

The warning/deprecation error was gone.

I tried remove the "import androidx.lifecycle.observe" and converted our observers like the following:

// From this
livedata.observe(viewLifecycleOwner, Observer<MyClass?> {
    // do stuff with it
})

// To this
livedata.observe(viewLifecycleOwner) {
    // do stuff with it
}

The issue occured when we need to remove the observer inside the onChange call, e.g.

    // From this
    livedata.observe(viewLifecycleOwner, object : Observer<MyClass?> {
        override fun onChanged(t: MyClass?) {
            // Do stuff with it t
            livedata.removeObserver(this)
        }
    })
    
    // To this
    livedata.observe(viewLifecycleOwner) {
        // do stuff with it
        livedata.removeObserver(this) <--- not working ofc
    }

I've heard rumors that folks have broken out the observer as a variable and thus been able to add/remove it by referencing the variable. However I'm unable to figure out how to instantiate a local observer without using the "Observer<MyClass?> syntax.

AndroidX extension is deprecated, so we have to use the original one.

Remove import androidx.lifecycle.observe

then

viewModel.liveData.observe(viewLifecycleOwner, Observer { result ->
    
})

or

viewModel.liveData.observe(viewLifecycleOwner) { result ->
                
}

It means that the extension in androidx is not needed anymore.

Simply remove its import import androidx.lifecycle.observe.

It will be actually deprecated in androidx. Read more reasoning there.

EDIT:

Please note the "issue" from Erik Hoogendoorn

This change causes values from the observed LiveData object to be interpreted as nullable(since the converted lambda syntax is based on nullable Java code). This was not the case for the Kotlin extension and causes a loss in functionality for the user. In my opinion this change should be reverted and a different solution found.

I'm curious if they will rename & retain the helper or come up with another solution.