android - 微调器 onItemSelected() 没有被调用

Question

我已经实现了一个 ArrayAdapter 来填充我的 Spinner View 。 Spinner 工作正常，但是当我单击微调器中的项目时，android 没有检测到。

我已遵守 spinner example in the Android docs 中的所有要求 包括在我的 Activity 中实现 AdapterView.OnItemSelectedListener 并覆盖它的两个方法 OnItemSelectedListener 和 onNothingSelected，但是，我的 Log 都没有> 这些方法中的语句会打印出来，因此不会被调用。

我还通过 choose_user.onItemSelectedListener = this@PlayerDetails 将监听器设置为我的微调器。

这是我的 Activity :

class PlayerDetails : AppCompatActivity(), View.OnClickListener, TextWatcher, AdapterView.OnItemSelectedListener {
    val TAG: String = "PlayerDetails"
    val FirebaseTAG: String = "FirebaseDebug"

    var numOfPlayers: Int = 1
    var currentPlayer: Int = 1

    var name: String = ""
    var age: Int = 0
    var genderId: Int = 0
    var genderResult: String = ""

    val db = FirebaseFirestore.getInstance()
    var users: MutableList<String> = mutableListOf()

    private lateinit var binding: ActivityPlayerDetailsBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val sharedPref = this@PlayerDetails.getPreferences(Context.MODE_PRIVATE)
        val applicationID: String? = sharedPref.getString("applicationID", null)

        binding = DataBindingUtil.setContentView(this, R.layout.activity_player_details)

        if (applicationID != null) {

            db.collection("phones").document(applicationID)
                .collection("users")
                .get()
                .addOnSuccessListener { result ->

                    for (document in result){
                        val name = document.get("name").toString()
                        users.add(name)
                    }
                }

            Log.d(FirebaseTAG, users.toString())
            val spinnerAdaptor = ArrayAdapter<String>(this@PlayerDetails, android.R.layout.simple_spinner_item, users)
            spinnerAdaptor.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
            choose_user?.adapter = spinnerAdaptor
            choose_user.onItemSelectedListener = this@PlayerDetails
        }

        val intent = getIntent()
        numOfPlayers = intent.getIntExtra("number_of_players", 1)
        next_details.setOnClickListener(this)
        player_name.addTextChangedListener(this)
        player_age.addTextChangedListener(this)
        gender.setOnCheckedChangeListener(object: RadioGroup.OnCheckedChangeListener {
            override fun onCheckedChanged(radiogroup: RadioGroup, checked: Int) {
                if (fieldsArePopulated()) next_details.visibility = View.VISIBLE
            }
        })

    }

    override fun onItemSelected(parent: AdapterView<*>?, name: View?, position: Int, rowId: Long) {
        val chosenName: String = parent?.getItemAtPosition(position).toString()
        Log.d("ChosenName", chosenName)
        Log.d("adapterclicked", "adapterclicked")

    }

    override fun onNothingSelected(parent: AdapterView<*>?) {
        Log.d("Nothing", "NOTHINGCALLED")
    }

...

知道问题出在哪里吗？

另外，当我在 Spinner 中选择一个项目时，我的 Spinner 旁边的 View 会移动，因此显然可以检测到它，但仍然没有调用 onItemSelected()。

Answer 1

我为 users MutableList 设置了一个初始值:

var users: MutableList<String> = mutableListOf("Choose User")

现在 onItemSelected() 已成功调用。