kotlinx.android.synthetic returns DialogFragment 中为空

Question

在开始之前，我已经阅读了 等措辞相似的帖子，但它们对我不起作用。

正如我在标题中所解释的，当我点击肯定按钮（在本例中为“确定”）时，我得到了一个 NPE。如果有人能指出我做错了什么，那就太好了！下面是我的设置的抽象版本

MainFragment.kt

class MainFragment: DialogFragment() {

    override fun onCreateDialog(savedInstanceState: Bundle?) =
            AlertDialog.Builder(context!!)
                .setView(FragmentMainBinding.inflate(LayoutInflater.from(context)).root)
                .setTitle(R.string.title_main)
                .setNegativeButton(R.string.cancel, null)
                .setPositiveButton(R.string.ok) { _, _ -> onPositiveButtonTapped() }
                .create()

    private fun onPositiveButtonTapped() {
        val g = arrayListOf(ground_nbr_edit_text.text.toString()) // NullPointerException
        // ...
    }

}

fragment_main.xml

<?xml version="1.0" encoding="utf-8"?>
<layout>
    <LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <EditText
            android:id="@+id/ground_nbr_edit_text"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />

    </LinearLayout>
</layout>

Answer 1

DialogFragment 在 onCreateDialog() 之后调用 onCreateView()，然后将该视图用于对话框的内容，替换您在 onCreateDialog() 中已经设置的任何内容。因此，将您的视图创建移动到 onCreateView():

class MainFragment: DialogFragment() {

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?) =
        FragmentMainBinding.inflate(inflater).root

    override fun onCreateDialog(savedInstanceState: Bundle?) =
            AlertDialog.Builder(context!!)
                .setTitle(R.string.title_main)
                .setNegativeButton(R.string.cancel, null)
                .setPositiveButton(R.string.ok) { _, _ -> onPositiveButtonTapped() }
                .create()

    private fun onPositiveButtonTapped() {
        val g = arrayListOf(ground_nbr_edit_text.text.toString()) // NullPointerException
        // ...
    }

}