Kotlin Type mismatch: inferred type is View! but TextView was expected

Question

Good day! Using Kotlin 1.1.51 in Android Studio 3.0, targeting Android API 26 to create RecyclerView with next ViewHolder, but receiving error on building the project:

Type mismatch: inferred type is View! but TextView was expected

So I can't find TextView directly to ViewHolder variable, but found around way - find View and after that cast with as TextView as you can see in the code for holder.textView. Doesn't look so good, so are there solutions how to prevent this error or is it a bug? The code of RecyclerView.Adapter:

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VH {
        val view = LayoutInflater.from(parent.context)
                .inflate(R.layout.custom_item_view, parent, false)
        return VH(view)
    }

    override fun onBindViewHolder(holder: VH, position: Int) {
        val event: TimelineEvent = items[position]

        // does not work because of error in VH class
        holder.timeView.text = event.time

        // works
        (holder.textView as TextView).text = event.text
    }

    class VH(itemView: View) : RecyclerView.ViewHolder(itemView) {
        // error: Type mismatch: inferred type is View! but TextView was expected
        val timeView: TextView = itemView.findViewById(R.id.timeline_item_time)

        // works fine
        val textView: View = itemView.findViewById(R.id.timeline_item_text)
    }

With the newer (than `1.1.51`) and in recent `1.2.71` recent Kotlin version the error has disappeared — Eduards Pozarickis, Nov 02 '18 at 09:37

score 5 · Answer 1 · answered Nov 10 '17 at 09:00

5

It seems like you're not on API level 26 or newer yet. That's when findViewById was changed so that it returns a generic T instead of the base View class, which enables you to use it from Kotlin in these ways.

You can either manually cast the result of the findViewById call as @AlexTa suggested in the other answer, or you can update your support library version to 26 or later - the latest currently is 27.0.0. These new versions are available from Google's Maven repository.

answered Nov 10 '17 at 09:00

zsmb13

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Sorry, I'm on API 26, will update my question with this info – Eduards Pozarickis Nov 10 '17 at 10:41
You might be targeting 26, but if you're extending `AppCompatActivity`, then it's the support library version that has to be at least the first stable release of 26. – zsmb13 Nov 10 '17 at 11:53
You know that supportlib version cannot be less than compileSdkVersion and compileSdkVersion cannot be less than targetSdkVersion? – Eduards Pozarickis Nov 10 '17 at 12:21

score 4 · Answer 2 · answered Nov 10 '17 at 08:56

4

You just need to cast found view as expected type, to do so:

val timeView: TextView = itemView.findViewById(R.id.timeline_item_time) as TextView

or

val timeView: TextView = itemView.findViewById<TextView>(R.id.timeline_item_time)

answered Nov 10 '17 at 08:56

AlexTa

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Thank you for your answer, but both solutions not working. First because of API 26 ir will show error `Type inference failed: Not enough information to infer parameter T in fun findViewById(id: Int): T! Please specify it explicitly.` For second Studio will suggest to remove explicit type argument but on building the same error of type mismatch will be shown. – Eduards Pozarickis Nov 10 '17 at 10:40

score 1 · Answer 3 · answered Aug 09 '21 at 13:10

This question is several years old, but maybe my answer will help someone who comes across this question after making a simple error like I just did.

I came across a similar error (mine was inferred type is View but ImageView was expected) and while I was reading the answers here, I realized that I had two layouts generated by the primary/detail template in Android Studio. I had changed an element (id/item_detail) from TextView to ImageView in res/layout/fragment_item_detail.xml, but I only did it for the regular layout, and not for the layout in res/layout-sw600dp/fragment_item_detail.xml

Since the same id had different types in the two layouts, the binding couldn't cast the associated view to ImageView. Instead, it fell back to the common parent, which is View.

Changing both elements to ImageView (which is what I wanted anyway) fixed the error.

So, one thing you need to do to avoid this sort of error is to make sure that layout elements with the same id in the same-named layout files have the same class across all layout folders.

Kotlin Type mismatch: inferred type is View! but TextView was expected

3 Answers3