android - 在 Kotlin 中创建微调器时，如何修复指定为非空的参数在 fragment 中的旋转屏幕上为空？

Question

大家好我的 fragment 中，我在我的 fragment 中添加了一个微调器和一些代码来计算痣但是当我旋转屏幕时它崩溃并抛出一个错误我不知道它为什么崩溃，当尝试检查对于 Non-null object 我不知道错误的原因是什么，这是错误:

java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull

这是我的第一个 fragment 文件:

private var mListener: OnFragmentInteractionListener? = null


override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    // Inflate the layout for this fragment
    return inflater!!.inflate(R.layout.fragment_first, container, false)
}

override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    //activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT)
    /*Find the id of spinner*/
    val spinner = lol

    /*set an adapter with strings array*/
    spinner.adapter = ArrayAdapter(activity, R.layout.support_simple_spinner_dropdown_item, resources.getStringArray(R.array.atoms)) as SpinnerAdapter

    /*set click listener*/
    spinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
        override fun onItemSelected(parent: AdapterView<*>, view: View, position: Int, id: Long) {
            val num = when (spinner.selectedItem.toString()) {
                "H" -> editText.setText("1")
                "He" -> editText.setText("4")
                "C" -> editText.setText("12")
                "O" -> editText.setText("16")
                else -> editText.setText("")
            }
        }

        override fun onNothingSelected(parent: AdapterView<*>) {
            /*Do something if nothing selected*/
        }



    }

    button.setOnClickListener {
        if (
        editText2.text.toString().length > 0 &&
                editText.text.toString().length > 0) {
            val num2 = editText.text.toString().toDouble()
            val num1 = editText2.text.toString().toDouble()
            val num = num1/num2
            textView.setText("$num moles")
        }
        else {
            textView.setText("Please Enter a correct value")
        }
    }
}

这是我的 fragment_first.xml 文件:

<android.support.constraint.ConstraintLayout
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <TextView
        android:id="@+id/textView"
        android:layout_width="294dp"
        android:layout_height="80dp"
        android:layout_weight="1"
        android:text="Amswer : No of Moles"
        android:textAlignment="center"
        android:textSize="20sp"
        app:layout_anchorGravity="right|top"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.556" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="143dp"
        android:layout_height="46dp"
        android:layout_weight="1"
        android:text="Amount in Grams "
        android:textAlignment="center"
        android:textSize="20sp"
        app:layout_anchorGravity="left|bottom"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.066"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.305" />

    <Spinner
        android:id="@+id/lol"
        android:layout_width="145dp"
        android:layout_height="57dp"

        app:layout_anchorGravity="left|top"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.07"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.136" />

    <Button
        android:id="@+id/button"
        android:layout_width="138dp"
        android:layout_height="43dp"
        android:text="Calculate"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.788" />

    <EditText
        android:id="@+id/editText"
        android:layout_width="148dp"
        android:layout_height="57dp"
        android:ems="10"
        android:hint="Gram"
        android:inputType="numberDecimal|number"
        app:layout_anchorGravity="bottom|center"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.762"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.137" />

    <EditText
        android:id="@+id/editText2"
        android:layout_width="148dp"
        android:layout_height="57dp"
        android:ems="10"
        android:hint="Gram"
        android:inputType="numberDecimal|number"
        app:layout_anchorGravity="center_horizontal|center"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.716"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.288" />

</android.support.constraint.ConstraintLayout>

Answer 1

添加 ?在

view = View?

这是代码

spinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
        override fun onItemSelected(parent: AdapterView<*>, view: View?, position: Int, id: Long) {
            val num = when (spinner.selectedItem.toString()) {
                "H" -> editText.setText("1")
                "He" -> editText.setText("4")
                "C" -> editText.setText("12")
                "O" -> editText.setText("16")
                else -> editText.setText("")
            }
        }