Kotlin. Unchecked cast: Any? to HashMap<String?, String?>?

Question

I want to get HashMap<String?, String?>? from firebaseDatabase:

override fun onDataChange(dataSnapshot: DataSnapshot) {
    val users: HashMap<String?, String?>? = dataSnapshot.value as HashMap<String?, String?>?  // todo !!!
    if (users != null) {
        if (!users.containsKey(userUid)) {
            users[userUid] = userName
        }
    }
}

This code works but Android Studio shows a warning on a 2nd line:

 Unchecked cast: Any? to HashMap<String?, String?>?

How to fix this in a proper way?

@Rainmaker so what's wrong?:) you can use suppress warning for unchecked cast. And btw you can omit : HashMap<String?, String?>? — Anton Kazakov
– Anton Kazakov, Commented Mar 10, 2018 at 12:48
@AntonKazakov I'd like to implement it in a safe way. What if someone changes data in firebase. I tried to check if it is Hashmap<String, String> but it doesn't work too — Rainmaker
– Rainmaker, Commented Mar 10, 2018 at 13:07

Narasimman P · Accepted Answer · 2019-12-13 10:49:47Z

7

You can use @Suppress("UNCHECKED_CAST")

(eg)

@Suppress("UNCHECKED_CAST")
val users: HashMap<String?, String?>? = dataSnapshot.value as HashMap<String?, String?>?

answered Dec 13, 2019 at 10:49

Narasimman P

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Comments

Ronan Boiteau · Accepted Answer · 2018-03-16 09:36:05Z

6

The approach with GenericTypeIndicator works, thank you @leoderprofi

    val ti = object : GenericTypeIndicator<HashMap<String?, String?>?>() {}
    //...
    override fun onDataChange(dataSnapshot: DataSnapshot) {
        val users: HashMap<String?, String?>? = dataSnapshot.getValue(ti)
        if (users != null) {
            if (!users.containsKey(userUid)) {
                users[userUid] = userName
            }
        }
    }

edited Mar 16, 2018 at 9:36

Ronan Boiteau

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answered Mar 10, 2018 at 17:00

Rainmaker

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1 Comment

Ponomarenko Oleh Over a year ago

Where is from the GenericTypeIndicator?

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