Anko LiveData Binding

Anko+.kt

class LifecycleGetter<T : View>(var lifecycleOwner: LifecycleOwner, var view: T)

fun <T : View> T.observe(lifecycleOwner: LifecycleOwner): LifecycleGetter<T> {
  return LifecycleGetter(lifecycleOwner, this)
}

fun <T : TextView> LifecycleGetter<T>.liveText(liveData: LiveData<String>): LifecycleGetter<T> {
  liveData.observe(lifecycleOwner, Observer {
    this.view.text = it
  })
  return this
}

fun <T : View, X> LifecycleGetter<T>.liveVisibility(liveData: LiveData<X>, isVisibleAtNull: Boolean = false): LifecycleGetter<T> {
  liveData.observe(lifecycleOwner, Observer {
    if (isVisibleAtNull) this.view.isVisible = it == null
    else this.view.isVisible = it != null
  })
  return this
}

fun <T : ImageView> LifecycleGetter<T>.liveUrlImage(liveData: LiveData<String>): LifecycleGetter<T> {
  liveData.observe(lifecycleOwner, Observer {
    Glide.with(this.view)
        .load(it)
        .apply(RequestOptions.circleCropTransform())
        .into(this.view)
  })
  return this
}

fun <T : View> LifecycleGetter<T>.bind(): T {
  return this.view
}

Example.kt

data class User(var name : String, var profileImage : String)

val lifecycleOwner = //.. can be Activity, Fragment or Something

val _userLiveData = MutableLiveData<User>()
val userLiveData : LiveData<User>() get() = _userLiveData

fun <T, R> LiveData<T>.map(f: (T) -> R): LiveData<R> = Transformations.map(this, f)

// Layout will visible when User from userLiveData is not null. (liveVisibility)
// if userLiveData is not null, automatically observe data,
// and provide profileImage to imageView (In my case, Glide), set user name to textView.
// Observer lifecycle depends on observe(LifecycleOwner)

verticalLayout {
  
  imageView()
    .observe(lifecycleOwner) // LifecycleGetter Scope
    .liveUrlImage(userLiveData.map { it.profileImage })
    .bind() // return ImageView
    .lparams(dip(56), dip(56)) { bottomMargin = dip(24) }
 
  textView()
    .observe(lifecycleOwner) // LifecycleGetter Scope
    .liveText(userLiveData.map { it.name })
    .bind() // return TextViewView
    .lparams(matchParent)
  
}.observe(lifecycleOwner).liveVisibility(userLiveData).bind()