Java 片段NullPointException

我只是想在片段中获取编辑文本的值，并通过创建一个String函数在textView中显示它，然后返回text->String和另一个String函数，以从片段中的edittext返回值，并在我的MainActivity中使用按钮Save（仅用于测试）显示它，但它一直给我这个错误：

 java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
 at com.example.Thisporject.fragment.fragment_fr_Person.TogetNameText(fragment_fr_Person.java:97)
at com.example.Thisporject.CreateGame.CreateGameGenerated.getNameEditText(CreateGameGenerated.java:60)
        at com.example.Thisporject.CreateGame.CreateGameGenerated.SaveAllContent(CreateGameGenerated.java:79)

FragmentActivity.Java：

public class fragment_fr_Person extends Fragment  {
    View rootView;
    EditText NameEdit;
@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        rootView =  inflater.inflate(R.layout.fragment_fr_person, container, false);
        NameEdit = rootView.findViewById(R.id.Name_Editext);


       



        return rootView;
    }

    public String TogetNameText(){
        return NameEdit.getText().toString();
    }
}

 public class CreateGameGenerated extends FragmentActivity {
    Button Save_btn;
    ImageView displayImage;
    FloatingActionButton addPhotoFloating_btn;
    fragment_list frag;
    List<fragment_list> qqf = new ArrayList<>();




    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.create_game_generated);
        Save_btn = findViewById(R.id.Save_btn);
        displayImage = findViewById(R.id.display_ImageView);
        addPhotoFloating_btn = findViewById(R.id.photo_gallery_acess_btn);
        TextView testName = findViewById(R.id.testName);
        TextView testAge = findViewById(R.id.testAge);


        Spinner spinner = findViewById(R.id.tags_spinner);
        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.tags, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adapter);

        Save_btn.setOnClickListener(this::SaveAllContent);
    }


    public  String getNameEditText(){
        fragment_fr_Person fragment_fr_person;
        fragment_fr_person = new fragment_fr_Person();
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.disallowAddToBackStack();
        fragmentTransaction.commitNowAllowingStateLoss();

        return fragment_fr_person.TogetNameText();
    }

    public String getAgeEditText(){
        fragment_fr_Person fragment_fr_person;
        fragment_fr_person = new fragment_fr_Person();
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.disallowAddToBackStack();
        fragmentTransaction.commitNowAllowingStateLoss();
        //Handler

        return fragment_fr_person.TogetAgeText();

    }

    private void SaveAllContent(View view) {
        TextView testName = findViewById(R.id.testName);
        TextView testAge = findViewById(R.id.testAge);

        testName.setText(getNameEditText());
        testAge.setText(getAgeEditText());

    }


}

MainActivity.Java：

public class fragment_fr_Person extends Fragment  {
    View rootView;
    EditText NameEdit;
@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        rootView =  inflater.inflate(R.layout.fragment_fr_person, container, false);
        NameEdit = rootView.findViewById(R.id.Name_Editext);


       



        return rootView;
    }

    public String TogetNameText(){
        return NameEdit.getText().toString();
    }
}

 public class CreateGameGenerated extends FragmentActivity {
    Button Save_btn;
    ImageView displayImage;
    FloatingActionButton addPhotoFloating_btn;
    fragment_list frag;
    List<fragment_list> qqf = new ArrayList<>();




    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.create_game_generated);
        Save_btn = findViewById(R.id.Save_btn);
        displayImage = findViewById(R.id.display_ImageView);
        addPhotoFloating_btn = findViewById(R.id.photo_gallery_acess_btn);
        TextView testName = findViewById(R.id.testName);
        TextView testAge = findViewById(R.id.testAge);


        Spinner spinner = findViewById(R.id.tags_spinner);
        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.tags, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adapter);

        Save_btn.setOnClickListener(this::SaveAllContent);
    }


    public  String getNameEditText(){
        fragment_fr_Person fragment_fr_person;
        fragment_fr_person = new fragment_fr_Person();
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.disallowAddToBackStack();
        fragmentTransaction.commitNowAllowingStateLoss();

        return fragment_fr_person.TogetNameText();
    }

    public String getAgeEditText(){
        fragment_fr_Person fragment_fr_person;
        fragment_fr_person = new fragment_fr_Person();
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.disallowAddToBackStack();
        fragmentTransaction.commitNowAllowingStateLoss();
        //Handler

        return fragment_fr_person.TogetAgeText();

    }

    private void SaveAllContent(View view) {
        TextView testName = findViewById(R.id.testName);
        TextView testAge = findViewById(R.id.testAge);

        testName.setText(getNameEditText());
        testAge.setText(getAgeEditText());

    }


}

public类CreateGameGenerated扩展碎片活动{
按钮保存按钮；
图像视图显示图像；
浮动操作按钮添加光浮动\u btn；
碎片列表碎片；
List qqf=new ArrayList（）；
@凌驾
创建时受保护的void（@Nullable Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.create_game_generated）；
Save_btn=findviewbyd（R.id.Save_btn）；
displayImage=findviewbyd（R.id.display\u ImageView）；
addPhotoFloating\u btn=findviewbyd（R.id.photo\u gallery\u access\u btn）；
TextView testName=findviewbyd（R.id.testName）；
TextView testAge=findviewbyd（R.id.testAge）；
微调器微调器=findViewById（R.id.tags\u微调器）；
ArrayAdapter=ArrayAdapter.createFromResource（这个，R.array.tags，android.R.layout.simple\u微调器\u项）；
setDropDownViewResource（android.R.layout.simple\u微调器\u下拉菜单\u项）；
旋转器。设置适配器（适配器）；
Save_btn.setOnClickListener（this:：SaveAllContent）；
}
公共字符串getNameEditText（）{
碎片人碎片人；
fragment_fr_person=新的fragment_fr_person（）；
FragmentTransaction FragmentTransaction=getSupportFragmentManager（）.beginTransaction（）；
fragmentTransaction.disallowAddToBackStack（）；
fragmentTransaction.commitNowAllowingStateLoss（）；
返回片段_fr_person.TogetNameText（）；
}
公共字符串getAgeEditText（）{
碎片人碎片人；
fragment_fr_person=新的fragment_fr_person（）；
FragmentTransaction FragmentTransaction=getSupportFragmentManager（）.beginTransaction（）；
fragmentTransaction.disallowAddToBackStack（）；
fragmentTransaction.commitNowAllowingStateLoss（）；
//处理者
返回fragment_fr_person.togetext（）；
}
私有void SaveAllContent（视图）{
TextView testName=findviewbyd（R.id.testName）；
TextView testAge=findviewbyd（R.id.testAge）；
setText（getNameEditText（））；
setText（getAgeEditText（））；
}
}

fragment.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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/EditTextMainContainer"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    app:layout_constraintTop_toBottomOf="@id/ImageViewAndEdit"
    app:layout_constraintStart_toStartOf="parent"
    tools:context="com.example.ThisProject.fragment.fragment_fr_Person">

    <RelativeLayout
        android:layout_marginTop="10dp"
        android:id = "@+id/NameContainer"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content">
    <TextView
        android:id="@+id/textViewName"
        android:text="@string/TextName"
        android:textColor="@color/black"
        android:textStyle="bold"
        android:textSize="20sp"
        android:layout_marginStart="8dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <EditText
        android:id="@+id/Name_Editext"
        android:padding="10dp"
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="10dp"
        android:layout_marginEnd="8dp"
        android:autofillHints="@string/template"
        android:layout_below="@id/textViewName"
        android:background="@drawable/custom_input"
        android:hint="@string/insert_here" />
</RelativeLayout>
</RelativeLayout>

maintactivy.xml

            <androidx.fragment.app.FragmentContainerView
                android:id ="@+id/fragment_generated_mainView"
                android:name="com.example.ThisProject.fragment.fragment_fr_Person"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                app:layout_constraintTop_toBottomOf="@id/tags_spinner"
                />
            <TextView android:id ="@+id/testName"
                android:layout_height="wrap_content"
                android:layout_width="wrap_content"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toBottomOf="@id/ImageViewAndEdit"/>

---

您应该将代码从EditText获取值移动到onViewCreated。这将在创建视图后执行代码。还要检查布局中是否存在R.id.Name\u Editext R.layout.fragment\u fr\u person

@Override
        public void onViewCreated(View view, Bundle savedInstanceState) {
            super.onViewCreated(view, savedInstanceState);
NameEdit = (EditText) rootView.findViewById(R.id.Name_Editext);
}

---

getNameEditText

我觉得这个方法不对

---

您应该使用

findFragmentById（）

获取片段，或者在实例化时将其保存到变量中。然后你可以从你的活动中调用你的

mFragment.TogetNameText（）

，

R.id.NameEdit

确实存在，我把它放在了onViewCreated中，但是到目前为止没有任何效果。在findViewById调用之前添加（EditText）cast。