Observable(LiveData/Rx) Bind Extensions

Often times I find myself observing simple values from LiveData or Rx observables and setting them to view items like TextViews or EditTexts. Or setting visibility of a Button or TextView.

Well, it looks ugly to me. We can do it more readable. RxSwift has bind() function to simply do this operation.

It binds ViewModel value to Label or Image Field

In order to achieve something similar, we can use Extension functions. So I created a file that called ReactiveBindExtensions in our project.

With the help of these extension functions, we can convert our bindings into much readable and clean version. Even cleaner than RxSwift bind() function 🙂

You can find the sample extension code in this gist.

	import android.graphics.Bitmap
	import android.graphics.drawable.Drawable
	import android.view.View
	import android.widget.ImageView
	import android.widget.TextView
	import androidx.lifecycle.LifecycleOwner
	import androidx.lifecycle.LiveData
	import androidx.lifecycle.Observer
	import com.jakewharton.rxrelay2.BehaviorRelay
	import io.reactivex.disposables.CompositeDisposable
	import io.reactivex.rxkotlin.addTo

	fun <T> LiveData<T>.bindText(lifecycleOwner: LifecycleOwner, textView: TextView?) {
	this.observe(lifecycleOwner, Observer { textView?.text = it.toString() })
	}

	fun LiveData<Bitmap>.bindBitmap(lifecycleOwner: LifecycleOwner, imageView: ImageView?) {
	this.observe(lifecycleOwner, Observer { imageView?.setImageBitmap(it) })
	}

	fun LiveData<Drawable>.bindDrawable(lifecycleOwner: LifecycleOwner, imageView: ImageView?) {
	this.observe(lifecycleOwner, Observer { imageView?.setImageDrawable(value) })
	}

	fun LiveData<Boolean>.bindVisibility(lifecycleOwner: LifecycleOwner, view: View?) {
	this.observe(
	lifecycleOwner,
	Observer { value ->
	view?.visibility = if (value) View.VISIBLE else View.GONE
	})
	}

	fun <T> BehaviorRelay<T>.bindText(textView: TextView?, bag: CompositeDisposable) {
	this.subscribe { textView?.text = it.toString() }?.addTo(bag)
	}

	fun BehaviorRelay<Boolean>.bindVisibility(view: View?, bag: CompositeDisposable) {
	this.subscribe { view?.isSelected = it }?.addTo(bag)
	}