如何将文本从一个片段传递到另一个片段？两者都由 MainActivity

Question

我一直在尝试在Android Studio中使用Fragments，并成功实现了它。但是，当我尝试传递任何数据（此处为文本/字符串）时，出现空指针异常。

第二个片段似乎没有收到片段。这是代码：

MainActivity.java

public class MainActivity extends AppCompatActivity {

    TabLayout tb;
    ViewPager2 vp;
    viewPagerAdapter vpa;


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

        tb=findViewById(R.id.tab_lyt);
        vp= findViewById(R.id.pager);
        vpa= new viewPagerAdapter(this);

        vp.setAdapter(vpa);

        tb.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                vp.setCurrentItem(tab.getPosition());
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {

            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {

            }
        });

        vp.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
            @Override
            public void onPageSelected(int position) {
                super.onPageSelected(position);

                tb.getTabAt(position).select();
            }
        });
    }
}

activity_main.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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/tab_lyt"
        android:layout_marginTop="0dp" />

    <com.google.android.material.tabs.TabLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/tab_lyt">

        <com.google.android.material.tabs.TabItem
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Menu 1"/>

        <com.google.android.material.tabs.TabItem
            android:id="@+id/frag2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Menu 2"/>



    </com.google.android.material.tabs.TabLayout>




</RelativeLayout>

viewPagerAdapter.java

public class viewPagerAdapter extends FragmentStateAdapter {
    public viewPagerAdapter(@NonNull FragmentActivity fragmentActivity) {
        super(fragmentActivity);
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        switch (position)
        {
            case 0: return new frag1();

            case 1: return new frag2();

            default: return new frag1();
        }
    }

    @Override
    public int getItemCount() {
        return 2;
    }
}

frag1.java

public class frag1 extends Fragment {
    private EditText editText;
    private Button button;

    public frag1(){

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_frag1, container, false);

        editText = view.findViewById(R.id.frag1ET);
        button = view.findViewById(R.id.frag1btn);


        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String text = editText.getText().toString();
                Bundle bundle = new Bundle();
                bundle.putString("tex", text);
                Toast.makeText(getContext(), ""+bundle.toString(), Toast.LENGTH_LONG).show();
                frag2 f2 = new frag2();
                f2.setArguments(bundle);
                editText.setText("");
            }
        });

        return view;
    }
}

frag1.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    tools:context=".frgmnts.frag1">


    <EditText
        android:id="@+id/frag1ET"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="116dp"
        android:ems="10"
        android:hint="Enter text"
        android:inputType="textPersonName"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/frag1btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="28dp"
        android:text="Button"
        app:layout_constraintEnd_toEndOf="@+id/frag1ET"
        app:layout_constraintStart_toStartOf="@+id/frag1ET"
        app:layout_constraintTop_toBottomOf="@+id/frag1ET" />

    <TextView
        android:id="@+id/frag1tv"
        android:layout_width="260dp"
        android:layout_height="56dp"
        android:layout_marginTop="56dp"
        android:textAlignment="textStart"
        android:hint="Text from Frag 2"
        android:textSize="20sp"
        app:layout_constraintEnd_toEndOf="@+id/frag1ET"
        app:layout_constraintHorizontal_bias="0.506"
        app:layout_constraintStart_toStartOf="@+id/frag1ET"
        app:layout_constraintTop_toBottomOf="@+id/frag1btn" />
</androidx.constraintlayout.widget.ConstraintLayout>

frag2.java

public class frag2 extends Fragment {
    private TextView tv2;

    public frag2(){

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_frag2, container, false);

        tv2 = view.findViewById(R.id.frag2tv);


        return view;
    }

    @Override
    public void onResume() {
        super.onResume();
        Bundle bundle = getArguments();
        if (bundle != null) {
            String text = bundle.getString("tex");
            tv2.setText(text);
        }
        else
            tv2.setText("Text not received");
    }
}

frag2.xml

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".frgmnts.frag2">

    <EditText
        android:id="@+id/frag2ET"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="116dp"
        android:ems="10"
        android:hint="Enter text"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/frag2btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="40dp"
        android:text="Button"
        app:layout_constraintEnd_toEndOf="@+id/frag2ET"
        app:layout_constraintStart_toStartOf="@+id/frag2ET"
        app:layout_constraintTop_toBottomOf="@+id/frag2ET" />

    <TextView
        android:id="@+id/frag2tv"
        android:layout_width="260dp"
        android:layout_height="56dp"
        android:layout_marginTop="44dp"
        android:hint="Text from Frag 1"
        android:textAlignment="textStart"
        android:textSize="20sp"
        app:layout_constraintEnd_toEndOf="@+id/frag2ET"
        app:layout_constraintStart_toStartOf="@+id/frag2ET"
        app:layout_constraintTop_toBottomOf="@+id/frag2btn" />

</androidx.constraintlayout.widget.ConstraintLayout>

这方面的任何帮助和投入都会有所帮助。谢谢