FormFragment_1.kt

class FormFragment : Fragment() {

    private val section by lazy { arguments!!.getParcelable<Section>(SECTION) }
    private val fieldInputs = mutableListOf<FieldInput>()

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        val view = inflater.inflate(R.layout.form_section_fragment, container, false)
        return view
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        renderFields(view)
    }

    // This is the method which does the magic
    private fun renderFields(view: View) {
        val formContainer = view.findViewById<LinearLayout>(R.id.formContainer)

        //We iterate through each field and decide which component it corresponds to.
        //All of these components created by ourselves must follow the same interface, which is FieldInput<T>
        section.fields.forEach {
            val fieldInput: FieldInput = when(it.type) {
                FieldType.TEXT -> { TextInput(requireContext()) }
                FieldType.DATE -> { DateInput(requireContext()) }
                else -> {
                    throw IllegalStateException("unknown type")
                }
            }

            //we must set a key to each field so we send it back to the api as a map of the key and the value inserted
            fieldInput.apply {
                key = it.key
                setLabel(it.label)
            }

            //Then we add this field to the list of the fields, so we can validate all of them and get their values
            fieldInputs.add(fieldInput)
            
            //Our view only as a linear layout to hold the fields and place them one on each line
            formContainer.addView(fieldInput as View)
        }
    }

    companion object {
        const val SECTION = "section"

        fun newInstance(section: Section): FormFragment {
            val fragment = FormFragment()
            val bundle = Bundle().apply {
                putParcelable(SECTION, section)
            }
            fragment.arguments = bundle
            return fragment
        }
    }
}