由于空指针，无法在 TextView 中设置文本（）

Question

我有一个 MainActivity 片段，它有一个ListView。每个ListView 项目有三个TextViews。我制作了一个用于ListView 的自定义适配器，这个自定义适配器是我尝试在三个不同的TextView 上使用setText() 的地方。其中两个TextViews 能够更新，但问题是nameTextView.setText(singleAppt.getName()); 行。我认为问题在于 singleAppt.getName() 返回一个空值，因为 TextView 显示为空白，但我不确定它为什么为空。

自定义适配器：（问题就在这里）

public class AppointmentList extends ArrayAdapter<SingleAppointment> {
private Activity context;
List<SingleAppointment> appointments;

public AppointmentList(Activity context, List<SingleAppointment> appointments) {
    super(context, R.layout.layout_appt_list, appointments);
    this.context = context;
    this.appointments = appointments;
}

public void updateAppointmentList(List<SingleAppointment> appointments) {
    this.appointments = appointments;
}

@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
    LayoutInflater inflater = context.getLayoutInflater();
    View listViewItem = inflater.inflate(R.layout.layout_appt_list, null, true);

    TextView nameTextView = listViewItem.findViewById(R.id.nameTextView);
    TextView addressTextView = listViewItem.findViewById(R.id.addressTextView);
    TextView dateTextView = listViewItem.findViewById(R.id.dateTextView);

    SingleAppointment singleAppt = appointments.get(position);

    if(singleAppt != null && singleAppt.getName() != null) {
        nameTextView.setText(singleAppt.getName());
    }
    if(singleAppt != null && singleAppt.getAddress() != null) {
        addressTextView.setText(singleAppt.getAddress());
    }
    if(singleAppt != null && singleAppt.getDate() != null) {
        dateTextView.setText(singleAppt.getDate());
    }

   // addressTextView.setText(singleAppt.getAddress());
   // dateTextView.setText(singleAppt.getDate());

    return listViewItem;
}

}

MainActivity 片段：

public class Appointments extends Fragment {

View myView;

AppointmentList appointmentAdapter;
ArrayList<SingleAppointment> appointments;
ListView appointmentList;

DatabaseReference databaseAppointments;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
    databaseAppointments = FirebaseDatabase.getInstance().getReference("appointments");

    myView = inflater.inflate(R.layout.appointments, container, false);

    Button newApptButton = myView.findViewById(R.id.newApptButton);
    newApptButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent = new Intent(getActivity().getApplicationContext(), EditApptActivity.class);
            startActivity(intent);
        }
    });

    appointmentList = myView.findViewById(R.id.listView);
    appointments = new ArrayList<>();
    appointmentAdapter = new AppointmentList(getActivity(), appointments);
    appointmentList.setAdapter(appointmentAdapter);

    return myView;
}

@Override
public void onStart() {
    super.onStart();
    databaseAppointments.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            appointments.clear();
            for(DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                SingleAppointment singleAppt = postSnapshot.getValue(SingleAppointment.class);
                appointments.add(singleAppt);
            }
            appointmentAdapter.updateAppointmentList(appointments);
            appointmentAdapter.notifyDataSetChanged();
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}

}

用户编辑TextViews的活动：

public class EditApptActivity extends AppCompatActivity {

DatabaseReference databaseAppointments;
ArrayList<SingleAppointment> appointments;

Button bookButton;

EditText clientEditText;
EditText addressEditText;
EditText dateEditText;

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

    //Intent intent = getIntent();
    clientEditText = findViewById(R.id.clientEditText);
    addressEditText = findViewById(R.id.addressEditText);
    dateEditText = findViewById(R.id.dateEditText);

    databaseAppointments = FirebaseDatabase.getInstance().getReference("appointments");

    bookButton = findViewById(R.id.bookButton);
    bookButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            addAppointment();
            Intent intent = new Intent(getApplicationContext(), MainActivity.class);
            startActivity(intent);
        }
    });
}

private void addAppointment() {
    String name = clientEditText.getText().toString();
    String address = addressEditText.getText().toString();
    String date = dateEditText.getText().toString();

    if(!TextUtils.isEmpty(name) && !TextUtils.isEmpty(address) && !TextUtils.isEmpty(date)) {
        String id = databaseAppointments.push().getKey();
        SingleAppointment singleAppt = new SingleAppointment(id, name, address, date);
        databaseAppointments.child(id).setValue(singleAppt);

        clientEditText.setText("");
        addressEditText.setText("");
        dateEditText.setText("");
    } else {
        Toast.makeText(this, "Please enter a valid name, address, and date.", Toast.LENGTH_LONG).show();
    }
}

}

SingleAppointment.java 类（每个ListView 项目都是这些对象之一）：

public class SingleAppointment {
private String id;
private String clientName;
private String address;
private String date;

public SingleAppointment() {}

public SingleAppointment(String clientName, String address, String date) {
    this.clientName = clientName;
    this.address = address;
    this.date = date;
}

public SingleAppointment(String id, String clientName, String address, String date) {
    this.id = id;
    this.clientName = clientName;
    this.address = address;
    this.date = date;
}

public String getId() {
    return id;
}

public String getName() {
    return clientName;
}

public String getAddress() {
    return address;
}

public String getDate() {
    return date;
}

}

Answer 1

检查nameTextView的值是否为Null