科特林。未经检查的演员阵容：任何？到HashMap <string？，string？=“”>？

Question

我想从HashMap<String?, String?>?获取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
        }
    }
}

此代码有效，但Android Studio在第二行显示警告：

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

如何以正确的方式解决这个问题？

Answer 1

GenericTypeIndicator的方法有效，谢谢@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
            }
        }
    }

Answer 2

您可以使用@Suppress("UNCHECKED_CAST")

（例如）

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