android - kotlinx.android.synthetic 在 DialogFragment 中返回 null

Question

在我开始之前，我已经阅读了类似这样措辞的帖子，但它们对我不起作用。

正如我在标题中解释的那样，当我单击肯定按钮（在本例中为“确定”）时，我得到一个 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

主要片段.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>

标签： androidkotlinandroid-databinding

Answer 1

DialogFragment 调用onCreateView()之后onCreateDialog()，然后将该视图用于对话框的内容，替换您已经在onCreateDialog(). 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
        // ...
    }

}