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private lateinit var errorMessage: TextView
…
override fun onCreate(savedInstanceState: Bundle?) {
    …
    errorMessage = findViewById(R.id.error_message) as TextView
}

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private TextView errorMessage;
…
@Override
protected void onCreate(Bundle savedInstanceState) {
    errorMessage = (TextView) findViewById(R.id.error_message);
}

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fun <T : View> Activity.getViewById(@IdRes id: Int): T {
    return findViewById(id) as T
}

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private lateinit var errorMessage: TextView
…
override fun onCreate(savedInstanceState: Bundle?) {
    …
    errorMessage = getViewById(R.id.error_message)
}

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private val errorMessage: TextView by lazy { getViewById(R.id.error_message) }

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class ViewFinderDelegate<T : View> : ReadOnlyProperty<Activity, T> {
  
    private object EMPTY 
    private val id: Int
    private var view: Any? = Empty
  
    constructor(@IdRes id: Int) {
        this.id = id
    }
  

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private val errorMessage: TextView by ViewFinderDelegate(R.id.error_message)

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fun <T : View> Activity.view(IdRes id: Int): ReadOnlyProperty<Activity, T> 
    = ViewFinderDelegate(id)

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private val errorMessage: TextView by view(R.id.errorMessage)

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interface ContextProvdier {
    fun provideContext(): Context
}

class OwnActivity : AppCompatActivity(), ContextProvider {
    fun provideContext() = this
}

class OwnFragment : Fragment(), ContextProvider {
    fun provideContext() = context