您好，每次调用存在于名为“Firstfragment”的 Fragment 中的 Spinner 时，我的应用程序都会崩溃

如何解决您好，每次调用存在于名为“Firstfragment”的 Fragment 中的 Spinner 时，我的应用程序都会崩溃

   protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


//This Spinner is not located in the MainActivity but in A fragment
        Spinner s = (Spinner) findViewById(R.id.spinner33);

        s.setonItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> arg0,View arg1,int arg2,long arg3) {
                String msupplier=s.getSelectedItem().toString();
                 
                    Log.e("Selected item : ",msupplier);

            }
            @Override
            public void onnothingSelected(AdapterView<?> arg0) {

              
            }
        });

//Main MainActivity

<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:id="@+id/drawer">

<include

    layout="@layout/content_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<com.google.android.material.navigation.NavigationView
    android:id="@+id/nav_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_gravity="start"


    android:layout_marginTop="104dp"
    app:headerLayout="@layout/nav_header"
    app:menu="@menu/nav_menu" />


</androidx.drawerlayout.widget.DrawerLayout>

//第一个片段

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"

android:id="@+id/Fragment1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#2196F3"
tools:context=".MainActivity">


<ImageView
    android:id="@+id/imageView4"
    android:layout_width="match_parent"
    android:layout_height="773dp"
    android:src="@mipmap/background"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<LinearLayout
    android:id="@+id/linearLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/teal_700"
    android:orientation="horizontal"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent">

    <Button
        android:id="@+id/watBtn"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:clickable="true"
        android:drawabletop="@drawable/ic_baseline_looks_one_24"
        android:editable="true"
        android:enabled="true"
        android:focusable="auto"
        android:gravity="center"
        android:includeFontPadding="true"
        android:linksClickable="true"
        android:onClick="WattMthd"
        android:text="@string/WAT"
        app:backgroundTint="@android:color/holo_blue_dark"
        tools:layout_editor_absoluteX="35dp"
        tools:layout_editor_absoluteY="129dp" />

    <Button
        android:id="@+id/ampBtn"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:drawabletop="@drawable/ic_baseline_looks_two_24"
        android:editable="true"
        android:gravity="center"
        android:onClick="ampMthd"
        android:text="@string/AMP"
        android:textColorLink="#FFFFFF"
        app:backgroundTint="@android:color/darker_gray" />

    <Button
        android:id="@+id/voltBtn"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:drawabletop="@drawable/ic_baseline_looks_3_24"
        android:editable="true"
        android:gravity="center"
        android:onClick="voltMthd"
        android:text="فولت"
        app:backgroundTint="@android:color/holo_blue_dark" />

    <Button
        android:id="@+id/kWbtn"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:drawabletop="@drawable/ic_baseline_looks_4_24"
        android:editable="true"
        android:gravity="center"
        android:onClick="kWMthd"
        android:text="كيلو"
        app:backgroundTint="@android:color/holo_blue_dark" />
</LinearLayout>

<Spinner
    android:id="@+id/spinner33"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"

    android:background="@android:color/darker_gray"

    android:dropDownWidth="match_parent"
    android:entries="@array/SpinerConvertFrom"
    android:foreground="@drawable/ic_baseline_arrow_drop_down_circle_24"
    android:foregroundGravity="left|center"
    android:gravity="center"
    android:textAlignment="center"
    android:visibility="visible"
    app:flow_verticalAlign="center"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/linearLayout" />

<com.google.android.material.textfield.TextInputLayout
    android:id="@+id/textInputLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/spinner33">

    <com.google.android.material.textfield.TextInputEditText
        android:id="@+id/Text1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="@string/AMP"
        android:inputType="numberDecimal"
        android:selectAllOnFocus="true"
        android:textAlignment="center" />
</com.google.android.material.textfield.TextInputLayout>

<com.google.android.material.textfield.TextInputLayout
    android:id="@+id/textInputLayout3"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/textInputLayout">

    <com.google.android.material.textfield.TextInputEditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="@string/Volt"
        android:inputType="numberDecimal"
        android:selectAllOnFocus="true"
        android:textAlignment="center" />
</com.google.android.material.textfield.TextInputLayout>


</androidx.constraintlayout.widget.ConstraintLayout>

解决方法

如果您是从片段中调用微调器初始化，但它存在于主活动中它会崩溃，您需要在活动中调用它，或将其移动到 framgnet 的 xml。

,

activity_main 属于 MainActivity。所以有一个fragment_first 属于FirstFragment。您尝试初始化的微调器属于fragment_first，因此您必须在FirstFragment 中使用它或将其（微调器）移动到activity_main

,

你好，你的activity_main.xml里面你没有定义spinner，所以你不能得到你没有在xml文件中创建的视图，你可以从你的片段中获取它，或者你必须将Spinner移动到activity_main .xml。