SampleActivity.kt

class SampleActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_sample)

        // set toolbar as actionBar
        setSupportActionBar(home_toolbar)
        title = " "

        // build backdrop view
        backdrop_view
                .withToolbar(home_toolbar) // set a toolbar in backdrop
                .build() // do not forget to call this function
    }
}