如何在 Android Studio 中使用 Kotlin 检索在 onItemSelected 函数中修改的变量的值？

Question

我需要使用 when 检索在 onItemSelected 函数中修改的变量的值。这是我所做的：

    (...)

    private var i: Int = 0

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

        categorySpinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
            @SuppressLint("SetTextI18n")
            override fun onNothingSelected(parent: AdapterView<*>?) {

            }

            override fun onItemSelected(parent: AdapterView<*>?, view: View?, position: Int, id: Long) {
                category = categories[position]

                when (category) {
                    "Décès" -> i = 1
                    "Habitat" -> i = 2
                }
            }
        }

        binding.tvtest.text = i.toString()

        val acteSpinner: Spinner = binding.acteCreatingSpinnerActes
        when (i) {
            1 -> {
                val adapter = ArrayAdapter(this, android.R.layout.simple_spinner_item, actes[actes.indexOf(deces)])
                adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
                acteSpinner.adapter = adapter
                acte = acteSpinner.selectedItem.toString()
            }
            2 -> {
                val adapter = ArrayAdapter(this, android.R.layout.simple_spinner_item, actes[actes.indexOf(habitat)])
                adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
                acteSpinner.adapter = adapter
                acte = acteSpinner.selectedItem.toString()
            }
        }
    }
}

我试图在布局中检索变量 I 的值，我得到了 i = 0。
我想得到onItemSelected函数

中得到的值

Answer 1

不应在代码中使用硬字符串：“Décès”、“Habitat”
不需要变量。仅使用位置：

when (position) {
        0 -> {
            val adapter = ArrayAdapter(this, android.R.layout.simple_spinner_item, actes[actes.indexOf(deces)])
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
            acteSpinner.adapter = adapter
            acte = acteSpinner.selectedItem.toString()
        }
        1 -> {
            val adapter = ArrayAdapter(this, android.R.layout.simple_spinner_item, actes[actes.indexOf(habitat)])
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
            acteSpinner.adapter = adapter
            acte = acteSpinner.selectedItem.toString()
        } }

Answer 2

在回调中更改 class 成员没有问题，但是您编写的代码不起作用，因为回调不会立即运行 - 它运行s 稍后当用户单击某个项目时。

您似乎希望 acteSpinner 的适配器在您 select categorySpinner 中的内容时在两组不同的数据之间切换。您可以通过直接修改适配器中的数据来实现。这是您如何执行此操作的示例。

// You could make adapter a class member, but it is not necessary
// for this example
//private lateinit var adapter: ArrayAdapter<String>

override fun onCreate(savedInstanceState: Bundle?) {
    //...
    
    val binding = ...
    
    val adapter = ArrayAdapter(this, android.R.layout.simple_spinner_item)
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
    acteSpinner.adapter = adapter
    
    // Initially set the adapter to show list one
    adapter.addAll(firstList)
    binding.tvtest.text = "List One"
    
    categorySpinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
        @SuppressLint("SetTextI18n")
        override fun onNothingSelected(parent: AdapterView<*>?) {

        }

        override fun onItemSelected(parent: AdapterView<*>?, view: View?, position: Int, id: Long) {
            category = categories[position]
            // POINT B - Inside the callback. This code does not
            // run immediately, it runs later when an 
            // item is selected

            when (category) {
                "Décès" -> {
                    adapter.clear()
                    adapter.addAll(decesArray)
                    adapter.notifyDataSetChanged()
                    binding.tvtest.text = "Décès"
                    println("TEST: added deces ${decesArray.contentToString()}")
                }
                "Habitat" -> {
                    adapter.clear()
                    adapter.addAll(habitatArray)
                    adapter.notifyDataSetChanged()
                    binding.tvtest.text = "Habitat"
                    println("TEST: added habitat ${habitatArray.contentToString()}")
                }
            }
        }
    }

    // POINT A - Outside the callback
    //...
}

请注意“Point A”和“Point B”注释 - 在此代码中，“Point A”将运行首先，即使“Point B”位于较早的行中。如果您尝试使用您在“B 点”修改的变量在“A 点”做某事，它将不起作用。

Answer 3

试试这个

override fun onCreate(savedInstanceState: Bundle?) {

    categorySpinner.onItemSelectedListener = object : ItemSelected{
                    override fun onItemSelected(parent: AdapterView<*>?,   view: View?, position: Int, id: Long) {
            category = categories[position]

            when (category) {
                "Décès" ->  getItemSelected(1)
                "Habitat" ->  getItemSelected(2)
            }}}
}

private fun setDataSpinner(i: Int,actes: Actes){
    binding.tvtest.text = i.toString()
    val acteSpinner: Spinner = binding.acteCreatingSpinnerActes

    val adapter = ArrayAdapter(this, R.layout.simple_spinner_item, actes)
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
    acteSpinner.adapter = adapter
    acte = acteSpinner.selectedItem.toString()
}

private fun getItemSelected(item: Int){
    when(item){
        1 -> { setDataSpinner(item,actes[actes.indexOf(deces)]) }
        2 -> { setDataSpinner(item,actes[actes.indexOf(habitat)]) }
    }
}


interface ItemSelected: AdapterView.OnItemSelectedListener {
    override fun onItemSelected(parent: AdapterView<*>?, view: View?, position: Int, id: Long)
    override fun onNothingSelected(parent: AdapterView<*>?) {}
}

如何在 Android Studio 中使用 Kotlin 检索在 onItemSelected 函数中修改的变量的值？

How to retrieve the value of a variable modified in the onItemSelected function with Kotlin in Android Studio?

android

kotlin

case

spinner

onitemselectedlistener