Kotlin AndroidStudio 类型不匹配

Question

我的代码中有一些错误，Type mismatch. Required : FavoriteData, Found : FavoriteData? 用于行 dataFavorite = activity!!.intent.getParcelableExtra(EXTRA_NOTE) as FavoriteData 和 Type mismatch. Required : UserData, Found : UserData? 用于行 dataUser = activity!!.intent.getParcelableExtra(EXTRA_DATA) as UserData。

这是我的课：

class FollowersFragment : Fragment() {

private var listUser: ArrayList<UserData> = ArrayList()
private lateinit var adapter: FollowersAdapter
private var favorite: FavoriteData? = null
private lateinit var dataFavorite: FavoriteData
private lateinit var dataUser: UserData
private lateinit var progressBarFollowers: ProgressBar
private lateinit var recyclerViewFollowers: RecyclerView

companion object {
    private val TAG = FollowersFragment::class.java.simpleName
    const val EXTRA_DATA = "extra_data"
    const val EXTRA_NOTE = "extra_note"
}

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_followers, container, false)
}

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    progressBarFollowers = getView()!!.findViewById(R.id.progressBarFollowers)
    recyclerViewFollowers = getView()!!.findViewById(R.id.recyclerViewFollowers)

    adapter = FollowersAdapter(listUser)
    listUser.clear()

    favorite = activity!!.intent.getParcelableExtra(UserDetailActivity.EXTRA_NOTE)
    if (favorite != null) {
        dataFavorite = activity!!.intent.getParcelableExtra(EXTRA_NOTE) as FavoriteData
        showUserFollowers(dataFavorite.username.toString())
    } else {
        dataUser = activity!!.intent.getParcelableExtra(EXTRA_DATA) as UserData
        showUserFollowers(dataUser.username.toString())
    }

}

private fun showUserFollowers(id: String) {
    progressBarFollowers.visibility = View.VISIBLE
    val client = AsyncHttpClient()
    client.addHeader("User-Agent", "request")
    client.addHeader("Authorization", "token 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")
    val url = "https://api.github.com/users/$id/followers"
    client.get(url, object : AsyncHttpResponseHandler(){
        override fun onSuccess(
            statusCode: Int,
            headers: Array<Header>,
            responseBody: ByteArray
        ) {
            progressBarFollowers.visibility = View.INVISIBLE
            val result = String(responseBody)
            Log.d(TAG, result)
            try {
                val jsonArray = JSONArray(result)
                for (i in 0 until jsonArray.length()) {
                    val jsonObject = jsonArray.getJSONObject(i)
                    val username: String = jsonObject.getString("login")
                    showUserDetail(username)
                }
            } catch (e: Exception) {
                Toast.makeText(activity, e.message, Toast.LENGTH_SHORT)
                        .show()
                e.printStackTrace()
            }
        }

        override fun onFailure(
            statusCode: Int,
            headers: Array<Header>,
            responseBody: ByteArray,
            error: Throwable
        ) {
            progressBarFollowers.visibility = View.INVISIBLE
            val errorMessage = when (statusCode) {
                401 -> "$statusCode : Bad Request"
                403 -> "$statusCode : Forbidden"
                404 -> "$statusCode : Not Found"
                else -> "$statusCode : ${error.message}"
            }
            Toast.makeText(activity, errorMessage, Toast.LENGTH_LONG)
                    .show()
        }

    })
}

private fun showUserDetail(id: String){
    progressBarFollowers.visibility = View.VISIBLE
    val client = AsyncHttpClient()
    client.addHeader("User-Agent", "request")
    client.addHeader("Authorization", "token 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")
    val url = "https://api.github.com/users/$id"
    client.get(url, object : AsyncHttpResponseHandler(){
        override fun onSuccess(statusCode: Int, headers: Array<Header>, responseBody: ByteArray) {
            progressBarFollowers.visibility = View.INVISIBLE
            val result = String(responseBody)
            Log.d(TAG, result)
            try {
                val jsonObject = JSONObject(result)
                val username: String = jsonObject.getString("login").toString()
                val name: String = jsonObject.getString("name").toString()
                val avatar: String = jsonObject.getString("avatar_url").toString()
                val company: String = jsonObject.getString("company").toString()
                val location: String = jsonObject.getString("location").toString()
                val repository: String? = jsonObject.getString("public_repos")
                val followers: String? = jsonObject.getString("followers")
                val following: String? = jsonObject.getString("following")
                listUser.add(
                        UserData(
                                username,
                                name,
                                avatar,
                                company,
                                location,
                                repository,
                                followers,
                                following
                        )
                )
                showRecyclerList()
            } catch (e: Exception) {
                Toast.makeText(activity, e.message, Toast.LENGTH_SHORT)
                        .show()
                e.printStackTrace()
            }
        }

        override fun onFailure(statusCode: Int, headers: Array<Header>, responseBody: ByteArray, error: Throwable) {
            progressBarFollowers.visibility = View.INVISIBLE
            val errorMessage = when (statusCode) {
                401 -> "$statusCode : Bad Request"
                403 -> "$statusCode : Forbidden"
                404 -> "$statusCode : Not Found"
                else -> "$statusCode : ${error.message}"
            }
            Toast.makeText(activity, errorMessage, Toast.LENGTH_LONG)
                    .show()
        }

    })

}

private fun showRecyclerList() {
    recyclerViewFollowers.layoutManager = LinearLayoutManager(activity)
    val listAdapter = FollowersAdapter(followerFilter)
    recyclerViewFollowers.adapter = adapter

    listAdapter.setOnItemClickCallback(object : FollowersAdapter.OnItemClickCallback{
        override fun onItemClicked(UserData: UserData) {

        }
    })
}

}

我不明白如何解决这个问题，感谢您的关注:)

Answer 1

我只是从你的问题中举一个例子：

您已声明：

private lateinit var dataFavorite: FavoriteData

这意味着FavoriteData 不能被认为是一个空值。

因此，当您从 parcelable 中获取数据时，由于某种原因它可能为 null，因此它会为您提供一个类型 FavoriteData?，该类型可以为 null，但无法直接分配。

有两种方法可以解决这个问题

1.) 添加非 Null 断言 (!!)，如果数据为 NULL，则会抛出 NullPointter

dataFavorite = (intent.getParcelableExtra(YOUR_KEY) as FavoriteData?)!!

2.) 使您的变量为 Nullable

private var dataFavorite: FavoriteData? = null

指定为

dataFavorite = intent.getParcelableExtra("") as FavoriteData?

根据您的用例进行选择，并为其他人做同样的事情