android - DialogFragment 监听器

Question

我有一个带有监听器的 DialogFragment，用于单击按钮以调用 fragment 中的函数。
我收到 lateinit property listener has not been initialized当我单击肯定按钮时。
对话 fragment

class CreateCollectionDialog: DialogFragment() {
    lateinit var listener: CreateCollectionDialogListener

    interface CreateCollectionDialogListener {
        fun onDialogPositiveClick(dialog: DialogFragment, collectionName: String)
        // fun onDialogNegativeClick(dialog: DialogFragment)
    }

    override fun onAttachFragment(childFragment: Fragment) {
        println("onAttachFragment")
        super.onAttachFragment(childFragment)
        listener = context as CreateCollectionDialogListener
        println(listener)
    }

    override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
        return activity?.let {
            val builder = AlertDialog.Builder(it)
            val inflater = requireActivity().layoutInflater
            builder.setView(inflater.inflate(R.layout.dialog_collection, null))
                .setPositiveButton("Create", DialogInterface.OnClickListener { dialog, id ->
                    // Create new collection
                    var newCollectionName = view?.findViewById<EditText>(R.id.newCollectionName)?.text.toString()
                    if (!newCollectionName.equals("") && newCollectionName != null) {
                        listener.onDialogPositiveClick(this, newCollectionName)
                    }
                })
                .setNegativeButton("Cancel", DialogInterface.OnClickListener { dialog, id ->
                    // User canceled dialog
                    // listener.onDialogNegativeClick(this)
                })
            builder.create()
        }?: throw IllegalStateException("Activity cannot be null")
    }

    override fun onStart() {
        super.onStart()
        val positive: Button = (dialog as AlertDialog?)!!.getButton(AlertDialog.BUTTON_POSITIVE)
        positive.setTextColor(resources.getColor(R.color.topColor))

        val negative: Button = (dialog as AlertDialog?)!!.getButton(AlertDialog.BUTTON_NEGATIVE)
        negative.setTextColor(Color.RED)
    }
}

fragment

class CollectionsFragment: Fragment(), CreateCollectionDialog.CreateCollectionDialogListener {
     override fun onOptionsItemSelected(item: MenuItem): Boolean {

        when (item.itemId) {
            R.id.add -> {
                val createDialog = CreateCollectionDialog()
                createDialog.show(fragmentManager!!, "")
                return true
            }
        }
        return false
    }

    override fun onDialogPositiveClick(dialog: DialogFragment, collectionName: String) {
        addNewCollection(collectionName)
    }
}

Answer 1

onAttachFragment当一个 fragment 作为该 fragment 的子项附加时调用，在这种情况下，从不也不需要。
使用onAttach(Context context)对于当前情况。对话框 fragment 没有 child 所以onAttachFragment永远不会被调用。
要从父 fragment 初始化监听器，请使用:

// inside fragment lifecycle methods like onviewcreated etc
listener = getParentFragment() as CreateCollectionDialogListener