LiveData NonNull Observers

LiveDataExtensions.kt

/**
* Extends LiveData allowing Kotlin DSL for onChanged callback usage
*/
fun <T> LiveData<T>.observeNonNull(lifecycleOwner: LifecycleOwner, onItem: (T) -> Unit) {
    this.observe(lifecycleOwner, object : NonNullObserver<T> {
        override fun onChangedNonNull(t: T) {
            onItem(t)
        }
    })
}

NonNullObserver.kt

/**
* Interface of our new observer, using default functions
*/
interface NonNullObserver<T>: Observer<T> {

    override fun onChanged(t: T?) {
        if (t != null) onChangedNonNull(t)
    }

    fun onChangedNonNull(t: T)
}

TestActivity.kt

class TestActivity: AppCompatActivity() {

    val liveData: LiveData<String> = MutableLiveData<String>()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
      
        // Observe the LiveData with our new extension
        liveData.observeNonNull(this) {
            Log.d("TestActivity", "Got: $it")
        }
    }
}