我无法修复这个错误。当我想从firebase中删除一个条目时，这个错误就会出现。
java.lang.NullPointerException:尝试调用虚拟方法"double com.educationalappspk.financemgt4ortho.ExpenseInfo.getTuition（）"，该方法位于一个空对象引用上，该对象引用位于com.google.firebase.database.Query$1.onDataChange（Query.java：191）上的com.educationalappspk.financemgt4ortho.TransactionActivityAdapter$2.onDataChange（事务活动适配器. java：157）上
public class TransactionActivityAdapter extends ArrayAdapter<TransactionData> {
private Activity context;
private List<TransactionData> transactionDataList;
private FirebaseUser user;
private String uid;
public TransactionActivityAdapter(Activity context, List<TransactionData> transactionDataList) {
super(context, R.layout.recent_transaction, transactionDataList);
this.context = context;
this.transactionDataList = transactionDataList;
}
@Override
public int getCount() {
return transactionDataList.size();
}
@Nullable
@Override
public TransactionData getItem(int position) {
return transactionDataList.get(position);
}
@NonNull
@Override
public View getView(final int position, @Nullable View convertView, @NonNull ViewGroup parent) {
LayoutInflater layoutInflater = context.getLayoutInflater();
View view = layoutInflater.inflate(R.layout.expenselist_child,null,false);
TransactionData transactionData = transactionDataList.get(position);
ImageButton imageButton = view.findViewById(R.id.expenseListDeleteButton);
imageButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//Toast.makeText(getContext(),"Item selected " + position,Toast.LENGTH_SHORT).show();
AlertDialog.Builder builder1 = new AlertDialog.Builder(context);
builder1.setMessage("Delete this transactions?");
builder1.setCancelable(true);
builder1.setPositiveButton(
"Yes",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
onDeleteItem(position);
}
});
builder1.setNegativeButton(
"No",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.cancel();
}
});
AlertDialog alert11 = builder1.create();
alert11.show();
}
});
TextView date,category,amount,type;
date = view.findViewById(R.id.expense_list_child_date);
category = view.findViewById(R.id.expense_list_child_category);
amount = view.findViewById(R.id.expense_list_child_amount);
type = view.findViewById(R.id.expense_list_child_type);
date.setText(transactionData.getDate());
category.setText(transactionData.getCategory());
amount.setText(String.valueOf(transactionData.getAmount()) );
type.setText(transactionData.getType());
return view;
}
public void onDeleteItem(final int position){
final TransactionData transactionData = transactionDataList.get(position);
user = FirebaseAuth.getInstance().getCurrentUser();
uid = user.getUid();
final DatabaseReference db = FirebaseDatabase.getInstance().getReference(uid).child("transactions");
SimpleDateFormat format = new SimpleDateFormat("dd/MM/yyyy");
try {
Date date = format.parse(transactionData.getDate());
DailyData dailyData = new DailyData(date);
if(Integer.parseInt(dailyData.getDay())/10==0){
String d = "0" + dailyData.getDay();
dailyData.setDay(d);
}
if(Integer.parseInt(dailyData.getMonth())/10==0){
String m = "0" + dailyData.getMonth();
dailyData.setMonth(m);
}
final DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference(uid).child("expenseInfo").child(dailyData.getYear()).child(dailyData.getMonth());
databaseReference.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
ExpenseInfo expenseInfo = dataSnapshot.getValue(ExpenseInfo.class);
Log.d("hi", "onDataChange: " +transactionData.getType());
if(transactionData.getCategory().equals("Food")){
expenseInfo.setFood(expenseInfo.getFood()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Rent")){
expenseInfo.setRent(expenseInfo.getRent()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Transportation")){
expenseInfo.setTransportation(expenseInfo.getTransportation()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Clothing")){
expenseInfo.setClothing(expenseInfo.getClothing()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Communication")){
expenseInfo.setCommunication(expenseInfo.getCommunication()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Books")){
expenseInfo.setBooks(expenseInfo.getBooks()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Electronics")){
expenseInfo.setElectronics(expenseInfo.getElectronics()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Project")){
expenseInfo.setProject(expenseInfo.getProject()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Treat")){
expenseInfo.setTreat(expenseInfo.getTreat()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Tuition")){
expenseInfo.setTuition(expenseInfo.getTuition()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Education")){
expenseInfo.setEducation(expenseInfo.getEducation()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Hangout")){
expenseInfo.setHangout(expenseInfo.getHangout()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Trip")){
expenseInfo.setTrip(expenseInfo.getTrip()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Utilities")){
expenseInfo.setUtilities(expenseInfo.getUtilities()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Services")){
expenseInfo.setServices(expenseInfo.getServices()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Fees")){
expenseInfo.setFees(expenseInfo.getFees()-transactionData.getAmount());
}
else if(transactionData.getCategory().equals("Tax")){
expenseInfo.setTax(expenseInfo.getTax()-transactionData.getAmount());
}
else {
if (expenseInfo != null) {
expenseInfo.setOthers(expenseInfo.getOthers()-transactionData.getAmount());
}
}
databaseReference.setValue(expenseInfo);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
} catch (ParseException e) {
e.printStackTrace();
}
final String transactionId = transactionData.getTransactionId();
db.keepSynced(true);
db.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
//Toast.makeText(getContext(),"on data change",Toast.LENGTH_SHORT).show();
for (DataSnapshot dataSnapshot1: dataSnapshot.getChildren()){
TransactionData transactionData1 = dataSnapshot1.getValue(TransactionData.class);
//Toast.makeText(getContext(),transactionId + " " + transactionData1.getTransactionId().toString(),Toast.LENGTH_SHORT).show();
if(transactionData1.getTransactionId().equals(transactionId)){
db.child(dataSnapshot1.getKey().toString()).removeValue();
transactionDataList.remove(position);
notifyDataSetChanged();
Toast.makeText(getContext(),"item deleted",Toast.LENGTH_SHORT).show();
break;
}
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
}Firebase json文件为
{
"F93sQbST7whWeT0ilYnahiO9wNo1": {
"calender": {
"2023": {
"02": {
"10": {
"deposit": 200,
"expense": 100
}
}
}
},
"expenseInfo": {
"2023": {
"02": {
"books": 0,
"clothing": 0,
"communication": 0,
"education": 0,
"electronics": 0,
"fees": 0,
"food": 100,
"hangout": 0,
"others": 0,
"project": 0,
"rent": 0,
"services": 0,
"tax": 0,
"transportation": 0,
"treat": 0,
"trip": 0,
"tuition": 0,
"utilities": 0
}
}
},
"transactions": {
"-NNw3hVUnakSVcZBKgEO": {
"amount": 200,
"category": "Tuition",
"date": "10/02/2023",
"transactionId": "-NNw3hVUnakSVcZBKgEO",
"type": "Deposit"
},
"-NNw3nf6RGcPEiCIGY2X": {
"amount": 100,
"category": "Food",
"date": "10/02/2023",
"transactionId": "-NNw3nf6RGcPEiCIGY2X",
"type": "Expense"
}
}
}
}我已尝试修复此问题，但无法完成。
1条答案
按热度按时间5cg8jx4n1#
您可以像下面这样检查空值。
对于NullPointerExceptions，您可以检查该特定值是否为非空。
希望这个有用。