Check Android SDK Version with Kotlin using when

Question

I want to check the Android SDK version at runtime. I tried it like so:

fun Context.getDrawableById(resId : Int) : Drawable {

    when (Build.VERSION.SDK_INT) {

        in Int.MIN_VALUE..20 -> return resources.getDrawable(resId)
        else -> return getDrawable(resId)
    }
}

I got a compiler warning "Call requires API Level 21 (current min is 19)". So I changed my code:

fun Context.getDrawableById(resId : Int) : Drawable {

    if (Build.VERSION.SDK_INT < 21)
        return resources.getDrawable(resId)
    else
        return getDrawable(resId)
}

No compiler warning.

My question is: is it possible to use when in this case without compiler warning? How?

Answer 1

Is it possible to use "when" in this case without compiler warning?

Yes, by using ContextCompat.getDrawable() instead of context.getDrawable():

fun View.getDrawable(resId : Int): Drawable? =
        when (Build.VERSION.SDK_INT) {
            in 1..20 -> resources.getDrawable(resId)
            else -> ContextCompat.getDrawable(context, resId)
        }

Note that ContextCompat.getDrawable() returns the optional type Drawable?.