如何在 Android 旋转时保留多选对话框中的选择？

Question

我有一个对话 select 一周中不止一天如下：

class DialogSettingsEnabledDays : DialogFragment() {
    override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {

        return activity.let {

            val selectedDaysValue = BooleanArray(7) { _ -> false }
            val selectedDaysIndex = ArrayList<Int>()

            val daysToIndexMap = mutableMapOf<String, Int>()
            val indexToDaysMap = mutableMapOf<Int, String>()
            val daysArray = resources.getStringArray(R.array.days_medium)
            for (i in 0..6) {
                daysToIndexMap[daysArray[i]] = i
                indexToDaysMap[i] = daysArray[i]
            }

            val prefs = it!!.getSharedPreferences(getString(R.string.shared_prefs_settings), Context.MODE_PRIVATE)
            val selectedDaysString = prefs.getString("enabled_days", getString(R.string.default_enabled_days))
            val selectedDays = selectedDaysString!!.split(", ")

            for (day in selectedDays) {
                selectedDaysValue[daysToIndexMap.getValue(day)] = true
                selectedDaysIndex.add(daysToIndexMap.getValue(day))
            }

            val enabledDaysBuilder = AlertDialog.Builder(it)
            enabledDaysBuilder
                .setTitle(R.string.settings_enabled_days)
                .setMultiChoiceItems(R.array.days_long, selectedDaysValue) { _, which, isChecked ->
                    if (isChecked)
                        selectedDaysIndex.add(which)
                    else if (selectedDaysIndex.contains(which))
                        selectedDaysIndex.remove(Integer.valueOf(which))
                }
                .setPositiveButton(R.string.dialog_ok) { _, _ ->
                    if (selectedDaysIndex.isEmpty()) {
                        Toast.makeText(it, "Select atleast one day !!", Toast.LENGTH_SHORT).show()
                    } else {
                        selectedDaysIndex.sort()
                        val selectedDaysList = mutableListOf<String>()
                        for (i in selectedDaysIndex) {
                            selectedDaysList.add(indexToDaysMap.getValue(i))
                        }
                        val editor = prefs.edit()
                        editor
                            .putString("enabled_days", selectedDaysList.joinToString())
                            .apply()
                        val enabledDays = it.findViewById<LinearLayout>(R.id.settings_enabled_days)
                        enabledDays.findViewById<TextView>(R.id.secondary_text).text = selectedDaysList.joinToString()
                    }
                }
                .setNegativeButton(R.string.dialog_cancel) { _, _ -> /* do nothing */ }

            enabledDaysBuilder.create()
        }
    }
}

我从 activity:

中以这种方式调用此对话框

findViewById<LinearLayout>(R.id.settings_enabled_days)
    .setOnClickListener {
        DialogSettingsEnabledDays().show(this.supportFragmentManager, null)
}

我的问题是我的 selection of days 在轮换时重置为默认值。默认情况下，我指的是存储在 SharedPreferences 中的 selection，即 .setMultiChoiceItems 中的 selectedDaysValue。假设，这些是弹出对话框的 selected 天数：

Mon, Tue, Wed, Thu, Fri

现在，我将 selection 更改为：

Mon, Tue

但是，当我旋转 phone 时，selection 设置回默认值：

Mon, Tue, Wed, Thu, Fri

如何在方向改变时保留我的 select离子？因为在我看到的一些应用程序中，对话框 selection 在旋转时保持不变。

Answer 1

Android 系统会自动恢复你的片段状态，而状态改变的片段实际上并没有被销毁，只是它的视图被重新创建，所以你的片段变量中的任何值都将保持原样，您所要做的就是将该变量值重新分配给您的视图，这里是参考 link https://inthecheesefactory.com/blog/fragment-state-saving-best-practices/en

Answer 2

好吧，这是我通过仅更改 DialogFragment 代码做出的最终解决方案：

更改要存储的数据范围：

override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
    return activity.let {
        val selectedDaysValue = BooleanArray(7) { _ -> false }
        val selectedDaysIndex = ArrayList<Int>()

至：

private var selectedDaysValue = BooleanArray(7) { _ -> false }
private var selectedDaysIndex = ArrayList<Int>()

override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
    return activity.let {

存储数据：

override fun onSaveInstanceState(outState: Bundle) {
    outState.putBooleanArray("selected_days_value", this.selectedDaysValue)
    outState.putIntegerArrayList("selected_days_index", this.selectedDaysIndex)
}

我读取数据的位置为：

val prefs = it!!.getSharedPreferences(getString(R.string.shared_prefs_settings), Context.MODE_PRIVATE)
val selectedDaysString = prefs.getString("enabled_days", getString(R.string.default_enabled_days))
val selectedDays = selectedDaysString!!.split(", ")

for (day in selectedDays) {
    selectedDaysValue[daysToIndexMap.getValue(day)] = true
    selectedDaysIndex.add(daysToIndexMap.getValue(day))
}

从保存状态读取为：

val prefs = activity!!.getSharedPreferences(getString(R.string.shared_prefs_settings), Context.MODE_PRIVATE)
if (savedInstanceState == null) {
    val selectedDaysString = prefs.getString("enabled_days", getString(R.string.default_enabled_days))
    val selectedDays = selectedDaysString!!.split(", ")

    for (day in selectedDays) {
        selectedDaysValue[daysToIndexMap.getValue(day)] = true
        selectedDaysIndex.add(daysToIndexMap.getValue(day))
    }
} else {
    with(savedInstanceState) {
        selectedDaysValue = getBooleanArray("selected_days_value")!!
        selectedDaysIndex = getIntegerArrayList("selected_days_index")!!
    }
}

如何在 Android 旋转时保留多选对话框中的选择？

How to retain selection in multi choice dialog in Android on rotation?

android

android-dialogfragment

kotlin

multichoiceitems