在Android中对话框片段不能将事件传递回调用片段？

Question

class DialogSubjectsProgress: DialogFragment() {
    internal lateinit var listener: TheDialogListener

    interface TheDialogListener {
        fun onDialogCancel(dialog: DialogFragment)
        fun onDialogDismiss(dialog: DialogFragment)
    }

    override fun onAttach(context: Context) {
        super.onAttach(context)
        listener = context as TheDialogListener
    }

    override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
        super.onCreateDialog(savedInstanceState)

        // show progress dialog
        val progressView = activity!!.layoutInflater.inflate(R.layout.dialog_progress_i, null)
        progressView.findViewById<TextView>(R.id.progress_message).text = "Fetching data"

        return activity!!.let {
            val progressBuilder = AlertDialog.Builder(it, R.style.ThemeOverlay_AppCompat_Dialog)
            progressBuilder
                .setView(progressView)
                .setOnCancelListener {
                    listener.onDialogCancel(this)
                }
                .setOnDismissListener {
                    listener.onDialogDismiss(this)
                }
                .create()
        }
    }
}

这是我的片段代码，根据文档，它是用于活动:

class FragmentSubjects: Fragment(), DialogSubjectsProgress.TheDialogListener {

    // other code

    private fun addSubject() {
        // show progress dialog
        val progressDialog = DialogSubjectsProgress()
        progressDialog.show(activity!!.supportFragmentManager, "null")

        // todo
        // progressDialog.dismiss()

    }

    override fun onDialogCancel(dialog: DialogFragment) {
        // User canceled the dialog
    }

    override fun onDialogDismiss(dialog: DialogFragment) {
        // Dialog's work is done
        // todo
    }

}

我在这里找到了一个解决方案，但我并不真正理解它，因为它是用Java编写的，我也不理解Java。我需要帮助Kotlin！！

---编辑----

java.lang.ClassCastException: com.example.kotlinappv3.MainActivity cannot be cast to com.example.kotlinappv3.DialogSubjectsProgress$TheDialogListener
        at com.example.kotlinappv3.DialogSubjectsProgress.onAttach(DialogSubjectsProgress.kt:27)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManager.java:1404)
        at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1784)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManager.java:1852)
        at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:802)
        at androidx.fragment.app.FragmentManagerImpl.executeOps(FragmentManager.java:2625)
        at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2411)
        at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2366)
        at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273)
        at androidx.fragment.app.FragmentManagerImpl$1.run(FragmentManager.java:733)
        at android.os.Handler.handleCallback(Handler.java:874)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:198)
        at android.app.ActivityThread.main(ActivityThread.java:6729)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

at com.example.kotlinappv3.DialogSubjectsProgress.onAttach(DialogSubjectsProgress.kt:27)

listener = context as TheDialogListener

Answer 1

在AddSubject方法中，而不是

activity!!.supportFragmentManager

使用：

childFragmentManager

在DialogFragment代码中，更改：

override fun onAttach(context: Context) {
    super.onAttach(context)
    listener = context as TheDialogListener
}

override fun onAttachFragment(childFragment: Fragment?) {
    super.onAttachFragment(childFragment)
    listener = context as TheDialogListener
}