Null Objektreferenz zwischen zwei Aktivitäten mit mehreren Fragmenten

Question

Der Fehler ist: ‚VOID android.widget.TableRow.setVisibility (int)‘ auf einer Null-Objektreferenz

sehr neu in Android Studio und Java und hat gearbeitet damit für ein paar Wochen. Grundsätzlich besteht das Problem darin, dass ich mehrere Aktivitäten mit jeweils mehreren Fragmenten habe. Einer von ihnen namens Calculator hat drei Fragmente und in fragemntCalc2 habe ich viele Tabellenzeilen, die ich über ein Drop-Down-Menü aus einem anderen Aktivitätsfragment, nämlich einem Profil und seinem zweiten Fragment, unsichtbar machen möchte.

public class Fragment2 extends Fragment { 

Context context; 
Spinner CourseNameSpinner1; 
Spinner QualificationSpinner1; 
Spinner ExamboardSpinner1; 
Spinner spinner_switch; 

public static Fragment2 newInstance() 
{ 
    Fragment2 fragment = new Fragment2(); 
    return fragment; 
} 

public Fragment2() {} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    View rootView = inflater.inflate(R.layout.fragment_profile2, container, false); 
    context = container.getContext(); 


    CourseNameSpinner1 = (Spinner) rootView.findViewById(R.id.CourseNameSpinner1); 
    QualificationSpinner1 = (Spinner) rootView.findViewById(R.id.QualificationSpinner1); 
    ExamboardSpinner1 = (Spinner) rootView.findViewById(R.id.ExamboardSpinner1); 
    spinner_switch = (Spinner) rootView.findViewById(R.id.spinner_switch); 

    //Course Dropdown 
    Spinner spinner2 = (Spinner) rootView.findViewById(R.id.CourseNameSpinner1); 
    ArrayAdapter<CharSequence> adapter2 = ArrayAdapter.createFromResource(context, R.array.Course_Array, android.R.layout.simple_spinner_item); 
    adapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); // Specify the layout to use when the list of choices appears 
    spinner2.setAdapter(adapter2); // Apply the adapter to the spinner 

    //Qualification Dropdown 
    Spinner spinner3 = (Spinner) rootView.findViewById(R.id.QualificationSpinner1); 
    ArrayAdapter<CharSequence> adapter3 = ArrayAdapter.createFromResource(context, R.array.Qualification_Array, android.R.layout.simple_spinner_item); 
    adapter3.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); // Specify the layout to use when the list of choices appears 
    spinner3.setAdapter(adapter3); // Apply the adapter to the spinner 

    //ExamBoard Dropdown 
    Spinner spinner4 = (Spinner) rootView.findViewById(R.id.ExamboardSpinner1); 
    ArrayAdapter<CharSequence> adapter4 = ArrayAdapter.createFromResource(context, R.array.Exam_Array, android.R.layout.simple_spinner_item); 
    adapter4.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); // Specify the layout to use when the list of choices appears 
    spinner4.setAdapter(adapter4); // Apply the adapter to the spinner 

    Spinner spinner23 = (Spinner) rootView.findViewById(R.id.spinner_switch); 
    ArrayAdapter<CharSequence> adapter23 = ArrayAdapter.createFromResource(context, R.array.Switch_Array, android.R.layout.simple_spinner_item); 
    adapter23.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); // Specify the layout to use when the list of choices appears 
    spinner23.setAdapter(adapter23); // Apply the adapter to the spinner 

    //ArrayAdapter<CharSequence> adapter2 = ArrayAdapter.createFromResource(context, R.array.Course_Array, android.R.layout.simple_spinner_item); 
    //Where context is, originally it was a this. 
    //Changed as the spinner isn't declared in main activity 
    //this is fragment java, therefore it needs context to declare the spinner 

    SharedPreferences sharedPref = context.getSharedPreferences("Units", context.MODE_PRIVATE); 
    int spinnerValue = sharedPref.getInt("UserCourseChoiceSpinner1", -1); 
    int spinnerValue2 = sharedPref.getInt("UserCourseChoiceSpinner2",-1); 
    int spinnerValue3 = sharedPref.getInt("UserCourseChoiceSpinner3",-1); 
    if(spinnerValue != -1) 

    CourseNameSpinner1.setSelection(spinnerValue); 
    QualificationSpinner1.setSelection(spinnerValue2); 
    ExamboardSpinner1.setSelection(spinnerValue3); 


    Button button = (Button) rootView.findViewById(R.id.button_savecourse); 
    button.setOnClickListener(new View.OnClickListener() 
    { 
     @Override 
     public void onClick(View v) 
     { 
      int userChoice = CourseNameSpinner1.getSelectedItemPosition(); 
      int userChoice2 = QualificationSpinner1.getSelectedItemPosition(); 
      int userChoice3 = ExamboardSpinner1.getSelectedItemPosition(); 

      SharedPreferences sharedPref = context.getSharedPreferences("Units", Context.MODE_PRIVATE); 
      SharedPreferences.Editor prefEditor = sharedPref.edit(); 

      prefEditor.putInt("UserCourseChoiceSpinner1",userChoice); 
      prefEditor.putInt("UserCourseChoiceSpinner2",userChoice2); 
      prefEditor.putInt("UserCourseChoiceSpinner3",userChoice3); 

      prefEditor.commit(); 

      Toast.makeText(context, "Data was saved successfully", Toast.LENGTH_LONG).show(); 
     } 
    }); 

    Spinner spinner_switch = (Spinner)rootView.findViewById(R.id.spinner_switch); 
    spinner_switch.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() 
    { 
     @Override 
     public void onItemSelected(AdapterView<?> parent, View view, int position, long id) 
     { 
      TableRow tableRow; 
      if (position != 1) 
      { 
       tableRow = (TableRow) getActivity().findViewById(R.id.table13); 
       tableRow.setVisibility(View.GONE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.table14); 
       tableRow.setVisibility(View.GONE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.table15); 
       tableRow.setVisibility(View.GONE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.table16); 
       tableRow.setVisibility(View.GONE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.table17); 
       tableRow.setVisibility(View.GONE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.table18); 
       tableRow.setVisibility(View.GONE); 

       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade13); 
       tableRow.setVisibility(View.GONE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade14); 
       tableRow.setVisibility(View.GONE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade15); 
       tableRow.setVisibility(View.GONE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade16); 
       tableRow.setVisibility(View.GONE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade17); 
       tableRow.setVisibility(View.GONE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade18); 
       tableRow.setVisibility(View.GONE); 

      } 
      else 
      { 
       tableRow = (TableRow) getActivity().findViewById(R.id.table13); 
       tableRow.setVisibility(View.VISIBLE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.table14); 
       tableRow.setVisibility(View.VISIBLE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.table15); 
       tableRow.setVisibility(View.VISIBLE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.table16); 
       tableRow.setVisibility(View.VISIBLE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.table17); 
       tableRow.setVisibility(View.VISIBLE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.table18); 
       tableRow.setVisibility(View.VISIBLE); 

       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade13); 
       tableRow.setVisibility(View.VISIBLE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade14); 
       tableRow.setVisibility(View.VISIBLE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade15); 
       tableRow.setVisibility(View.VISIBLE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade16); 
       tableRow.setVisibility(View.VISIBLE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade17); 
       tableRow.setVisibility(View.VISIBLE); 
       tableRow = (TableRow) getActivity().findViewById(R.id.tablegrade18); 
       tableRow.setVisibility(View.VISIBLE); 
      } 
     } 
     @Override 
     public void onNothingSelected(AdapterView<?> parent) 
     { 

     } 
    }); 
    return rootView; 
} 

}

Die Nullobjektreferenz ist auf der Linie

tableRow = (TableRow) getActivity().findViewById(R.id.table13); 
       tableRow.setVisibility(View.GONE); 

so würde ich den Rest übernehmen davon nicht funktioniert. Wiederum als Info, die Tabellen sind auf einem völlig anderen Aktivitätsfragment, also wie würde ich es so machen, dass das Fragment die Pfeilen finden kann, obwohl ich Kontext deklariere.

Answer 1

ändern wie diese

tableRow = (TableRow) rootView.findViewById(R.id.table13); 
      tableRow.setVisibility(View.GONE); 

und erklären rootView global, und Sie nehmen separate Variable für alle TableRow