Question

我无法让微调器正确处理从SQLite数据库中检索到的项目。我可以在下拉菜单中显示项目，但无法选择它们。如果我用简单的字符串数组替换了项目（questAddViewModel.categorylist），则微调器将正常工作。我只是无法弄清楚如何从数据库中填充列表以代替工作。

我正在使用会议室和Dao进行数据库调用。

更新：随附的屏幕截图用于说明。如果我单击第二张图片中的任何项目，则屏幕仅返回到第一张图片，而在微调框中未显示任何选择。如果我像在注释代码中一样尝试将selectedItem分配给一个字符串

window is not defined
    at eval (eval at compile (\node_modules\ejs\lib\ejs.js:618:12), <anonymous>:215:37)
    at returnedFn (\node_modules\ejs\lib\ejs.js:653:17)
    at tryHandleCache (\node_modules\ejs\lib\ejs.js:251:36)
    at View.exports.renderFile [as engine] (\node_modules\ejs\lib\ejs.js:482:10)
    at View.render (\node_modules\express\lib\view.js:135:8)
    at tryRender (\node_modules\express\lib\application.js:640:10)
    at Function.render (\node_modules\express\lib\application.js:592:3)
    at ServerResponse.render (\node_modules\express\lib\response.js:1012:7)
    at \controllers\productController.js:1274:8
    at \node_modules\mongoose\lib\model.js:4733:16
    at \node_modules\mongoose\lib\utils.js:263:16
    at \node_modules\mongoose\lib\aggregate.js:973:13
    at \node_modules\kareem\index.js:135:16
    at processTicksAndRejections (internal/process/task_queues.js:82:9)

它会告诉我它为空。

这是片段中微调器的代码：

//questCategorySelected = parent.getItemAtPosition(pos).toString()

这是我在ViewModel中的代码

//Setup Spinner for Quest Category
        val categorySpinnerAdapter = ArrayAdapter(application, android.R.layout.simple_spinner_item, questAddViewModel.categorylist) //
                categorySpinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
        binding.addQuestCategory.adapter = categorySpinnerAdapter
        binding.addQuestCategory.onItemSelectedListener = object : AdapterView.OnItemSelectedListener
        {
            override fun onItemSelected(parent: AdapterView<*>, view: View, pos: Int, id: Long) {
                // An item was selected. You can retrieve the selected item using
                // parent.getItemAtPosition(pos)
                //questCategorySelected = parent.getItemAtPosition(pos).toString()
                //Toast.makeText(application, "${parent.getItemAtPosition(pos).toString()} <-In Selected", Toast.LENGTH_LONG).show();
            }
            override fun onNothingSelected(parent: AdapterView<*>) {
                // Another interface callback
            }
        }

这就是我在道中所拥有的

private val uiScope = CoroutineScope(Dispatchers.Main + viewModelJob)
val categorylist = ArrayList<String>()

 init {
        populateCategorySpinner()
    }

    fun populateCategorySpinner()
    {
        uiScope.launch {
            populateCategorySpinnerList()
        }
    }

    private suspend fun populateCategorySpinnerList()
    {
        withContext(Dispatchers.IO)
        {
            val categorylistcursor = database.getQuestCategoryCursor()

            if (categorylistcursor.moveToFirst()) {
                do {
                    val category =
                        categorylistcursor.getString(categorylistcursor.getColumnIndexOrThrow("quest_category_name"))
                    categorylist.add(category);
                } while (categorylistcursor.moveToNext())
            }
            categorylistcursor.close();
        }
    }

我正在寻找一种解决方案，以获取从数据库游标检索到的列表，以便能够在微调器中正确选择。

Answer 1

您是否尝试过更改 questCategorySelected = parent.getItemAtPosition（pos）.toString（）

通过

questCategorySelected =（TextView）视图

Answer 2

感谢您的评论和回答。在阅读评论后，我实际上发现了这一点。似乎问题是由于对数据库的协程调用，实际上数组未填充数据。这很混乱，因为它显示在下拉列表中。在阅读了LiveData的更多内容并保持适配器更新后，我解决了该问题。我尝试了几种将数组从ViewModel传递到Fragment的方法，但是好像没有使用LiveData，由于数据库调用协程，列表总是丢失。如果有人有更好的方法，欢迎提出建议！谢谢！

以下是我的解决方法：

片段

//Setup Spinner for Quest Category with LiveData monitoring of the Category List
        var CategoryArray: Array<String>
        var categorySpinnerAdapter: ArrayAdapter<String>

        questAddViewModel.categorylist.observe(this, Observer
        {if (it != null && it.isNotEmpty()) {
            CategoryArray = toArray(questAddViewModel.categorylist.value!!)
            categorySpinnerAdapter = ArrayAdapter(application, android.R.layout.simple_spinner_item, CategoryArray) //
            categorySpinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
            binding.addQuestCategory.adapter = categorySpinnerAdapter
        }})

        binding.addQuestCategory.onItemSelectedListener = object : AdapterView.OnItemSelectedListener
        {
            override fun onItemSelected(parent: AdapterView<*>, view: View, pos: Int, id: Long) {
                // An item was selected. You can retrieve the selected item using
                // parent.getItemAtPosition(pos)
            }
            override fun onNothingSelected(parent: AdapterView<*>) {
                // Another interface callback
            }
        }

ViewModel

private val _categorylist = MutableLiveData<ArrayList<String>>()
    val categorylist: LiveData<ArrayList<String>>
        get() = _categorylist

 private suspend fun populateCategorySpinnerList()
    {
        withContext(Dispatchers.IO)
        {
            val categorylistcursor = database.getQuestCategoryCursor()
            val categorylistfromdb = ArrayList<String>()

            if (categorylistcursor.moveToFirst()) {
                do {
                    val category =
                        categorylistcursor.getString(categorylistcursor.getColumnIndexOrThrow("quest_category_name"))
                    categorylistfromdb.add(category);
                } while (categorylistcursor.moveToNext())
            }
            categorylistcursor.close();
            _categorylist.postValue(categorylistfromdb)
        }
    }

从数据库填充微调器项目

2 个答案: