android numberpicker for floating point numbers

Question

The user of our app should be able to adjust a floating point number. At the moment, I filled an ArrayAdapter with all possible values and attached it to a spinner.

This

Answer 1

In Kotlin, you can use this handy NumberPicker extension dialog which scales your Double values into a fitting Int range and converts the Int values back to Doubles before calling any of the callback. So it basicallly hides away the fact that NumberPicker only supports Int. It just feels like NumberPicker would actually support Double, try it out!

Here's the Fragment extension you need to copy & paste:

fun Fragment.showNumberPickerDialog(
    title: String,
    value: Double,
    range: ClosedRange,
    stepSize: Double,
    formatToString: (Double) -> String,
    valueChooseAction: (Double) -> Unit
) {
    val numberPicker = NumberPicker(context).apply {
        setFormatter { formatToString(it.toDouble() * stepSize) }
        wrapSelectorWheel = false

        minValue = (range.start / stepSize).toInt()
        maxValue = (range.endInclusive / stepSize).toInt()
        this.value = (value.toDouble() / stepSize).toInt()

        // NOTE: workaround for a bug that rendered the selected value wrong until user scrolled, see also: https://stackoverflow.com/q/27343772/3451975
        (NumberPicker::class.java.getDeclaredField("mInputText").apply { isAccessible = true }.get(this) as EditText).filters = emptyArray()
    }

    MaterialAlertDialogBuilder(context)
        .setTitle(title)
        .setView(numberPicker)
        .setPositiveButton("OK") { _, _ -> valueChooseAction(numberPicker.value.toDouble() * stepSize) }
        .setNeutralButton("Cancel") { _, _ -> /* do nothing, closes dialog automatically */ }
        .show()
}

Now you can use it like this (in a Fragment):

showNumberPickerDialog(
    title = "Your Weight",
    value = 75.0, // in kilograms
    range = 10.0 .. 300.0,
    stepSize = 0.1,
    formatToString = { "$it kg" },
    valueChooseAction = { saveNewWeight(it) }
)