java - Null pointer error when trying to clear a PieChart

Question

I am trying to clear an anyChart in onCreate before I call a method that sets it. The reason for doing so is because I am using a tabbed activity and everytime I go in and out of the activity and come back it duplicates my piechart. I have investigated how to do so but I get this error when I add the following two lines in on create before any method call Solution attempt ->

1. anyChart.clear();
2. anyChart.invalidate();

Error caused by solution -> Attempt to invoke virtual method 'java.lang.String com.anychart.core.Chart.getJsBase()' on a null object reference

public class Remember extends Fragment {
private AnyChartView anyChartView;
private TextView calories, fats, proteins, carbohydrates;
private final FirebaseAuth mAuth = FirebaseAuth.getInstance();
private final String userID = mAuth.getUid();
private double macroCalories, macroProteins, macroFats, macroCarbohydrates;

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.activity_monday, container, false);
    anyChartView = view.findViewById(R.id.pieChart);
    calories = view.findViewById(R.id.dailyCaloriesLeftTextView);
    fats = view.findViewById(R.id.dailyFatsTV);
    proteins = view.findViewById(R.id.dailyProteinsTV);
    carbohydrates = view.findViewById(R.id.dailyCarbsTV);
    anyChartView.clear();
    anyChartView.invalidate();
    setUpTextFields();
    return view;
}

public void setUpTextFields() {
    assert userID != null;
    DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("Macros").child(userID);
    databaseReference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot snapshot) {
            Macro macro = snapshot.getValue(Macro.class);
            assert macro != null;
            calories.setText(String.valueOf(macro.getCalorieConsumption()));
            fats.setText(String.valueOf(macro.getFats()));
            proteins.setText(String.valueOf(macro.getProteins()));
            carbohydrates.setText(String.valueOf(macro.getCarbohydrates()));
            macroFats = macro.getFats();
            macroProteins = macro.getProteins();
            macroCarbohydrates = macro.getCarbohydrates();
            setUpPieChart(macroFats,macroProteins,macroCarbohydrates);
        }

        @Override
        public void onCancelled(@NonNull DatabaseError error) {
            Toast.makeText(getContext(), "Error Occurred!" + error.getMessage(), Toast.LENGTH_SHORT).show();
        }
    });
}

public void setUpPieChart(double fats,double proteins,double carbohydrates) {
    String[] macros = new String[]{"Fat", "Protein", "Carbs"};
    Pie pie = AnyChart.pie();
    List<DataEntry> dataEntries = new ArrayList<>();
    double[] macrosValues = {fats, proteins, carbohydrates};
    for (int i = 0; i < macros.length; i++) {
        dataEntries.add(new ValueDataEntry(macros[i], macrosValues[i]));
    }
    pie.data(dataEntries);
    anyChartView.setChart(pie);
}

}

Answer 1

等待大神答复