CODEWITHSUNDEEP
androidkotlin
MaaAn13
MaaAn13

Reputation: 258

Type inference failed in Kotlin using PairList

lateinit var dataList: PairList<Car, People>

I want to retrieve specific position based on pair, so what I do is:

val pair = Pair(carObj, peopleObj)
val position = dataList.indexOf(pair as Pair<Car, People>)

But it give me an error of Type inference failed and asks me to explicitly show type. I think I've done it with as Pair<Car, People>, but it says that it's a redundant statement. Any ideas on where I went totally wrong? :)

PairList class:

public class PairList<F, S> extends ArrayList<Pair<F, S>> {

public boolean add(F first, S second) {
    return add(new Pair<>(first, second));
}

public void add(int index, F first, S second) {
    add(index, new Pair<>(first, second));
}

@Override
public int indexOf(Object o) {
    if (o instanceof Pair) {
        return super.indexOf(o);
    } else {
        for (int i = 0; i < size(); i++) {
            Pair<F, S> pair = get(i);
            if (pair != null) {
                if (pair.first.equals(o)) return i;
            } else {
                if (o == null) return i;
            }
        }
        for (int i = 0; i < size(); i++) {
            Pair<F, S> pair = get(i);
            if (pair != null) {
                if (pair.second.equals(o)) return i;
            } else {
                if (o == null) return i;
            }
        }
    }
    return -1;
}

public int indexOf(F first, S second) {
    for (int i = 0; i < size(); i++) {
        Pair<F, S> pair = get(i);
        if (pair != null) {
            if (pair.first.equals(first) && pair.second.equals(second)) {
                return i;
            }
        } else {
            if(first == null && second == null) {
                return i;
            }
        }
    }
    return -1;
}

Upvotes: 0

Views: 297

Answers (2)

Balu Sangem
Balu Sangem

Reputation: 712

You are using android.util.Pair in PairList.java and you created Pair(carObj, peopleObj) using kotlin.Pair;

So replace android.util.Pair; with import kotlin.Pair; in PairList.java everything will work.

Upvotes: 1

Brijesh Joshi
Brijesh Joshi

Reputation: 1857

Your PairList class is probably extending Pair class from android.util.Pair; and when you are using that in your kotlin file it is using kotlin.Pair. Caz of this you are getting Type inference failed. To overcome this you have two solution

  1. simply turn your java file to kotlin
  2. use Pair class in kotlin using import android.util.Pair.
    val pair = android.util.Pair(carObj, peopleObj)

Upvotes: 1

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