java.lang.NullPointerException problem in ListView

Question

I'm new to Android development and I'm trying to convert a string to a double, then round it off to 2 decimal places, then convert it back to string to display in a ListView. Here is my code:

public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent){

            String expenseCategory = getItem(position).getExpenseCategory();
            String expenseAmount = getItem(position).getExpenseAmount();
            String expenseEntryDate = getItem(position).getExpenseTodayEntry();

            Double eA = Double.parseDouble(expenseAmount);
            String eAnew = String.format("%.2f",eA);
            Expenses ex = new Expenses(eAnew, expenseCategory, expenseEntryDate);

            LayoutInflater inflater = LayoutInflater.from(mContext);
            convertView = inflater.inflate(mResource, parent, false);

            TextView expenseCategoryTextView = (TextView) convertView.findViewById(R.id.CategoryHistoryTV);
            TextView expenseDateEntryTextView = (TextView) convertView.findViewById(R.id.DateHistoryTV);
            TextView expenseAmountTextView = (TextView) convertView.findViewById(R.id.AmountHistoryTV);

            expenseCategoryTextView.setText(expenseCategory);
            expenseDateEntryTextView.setText(expenseEntryDate);
            expenseAmountTextView.setText(eAnew);

            expenseCategoryTextView.setTextColor(Color.RED);
            expenseDateEntryTextView.setTextColor(Color.RED);
            expenseAmountTextView.setTextColor(Color.RED);

            return convertView;
    }

And here is the error:

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.trim()' on a null object reference

it runs properly without:

Double eA = Double.parseDouble(expenseAmount);
String eAnew = String.format("%.2f",eA);

But instead it gives me an output like

1000.0000

I understand that it may be bad design, however declaring the expenseAmount as double does not work in other areas of my code for various reasons.

I've tried to use a condition to "catch" the null value as the error says but so far nothing works.

Ashish Karn · Accepted Answer · 2020-06-18 14:36:52Z

1

Modify your code where you have pointed the problem and add Null check there. Below I have mentioned the code sample.

String eAnew = "00.00";
        if(expenseAmount != null && !"null".equals(expenseAmount)){
            Double eA = Double.parseDouble(expenseAmount);
            eAnew = String.format("%.2f",eA);
        }

answered Jun 18, 2020 at 14:36

Ashish Karn

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Comments

Daniyal Irfan · Accepted Answer · 2020-06-18 14:03:35Z

0

First of all You have not posted your complete code in which you are doing converting from double to string and vice versa and second According to error 'java.lang.String java.lang.String.trim()' it means your string is null on which you are calling trim function.So make sure that string must have some value before calling this function trim.

answered Jun 18, 2020 at 14:03

Daniyal Irfan

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Comments

Bram Stoker · Accepted Answer · 2020-06-18 14:44:21Z

0

It seems that expenseAmount is null here. Try to give your items in your list a default expenseAmount value or handle the null case.

Like:

public class Expense { // whatever your class is

    private String expenseAmount = "0"; // set a default value, so it's not null

    ...
}

Or:

public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
    ...
    String expenseAmount = getItem(position).getExpenseAmount();
    ...

    String eAnew;
    if (expenseAmount == null) {
        eAnew = "I don't have an expenseAmount yet!"; // handle the null case

    else {
        Double eA = Double.parseDouble(expenseAmount);
        eAnew = String.format("%.2f", eA);
    }
    Expenses ex = new Expenses(eAnew, expenseCategory, expenseEntryDate);

    ...
}

edited Jun 18, 2020 at 14:44

answered Jun 18, 2020 at 14:06

Bram Stoker

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3 Comments

anonymous23 Over a year ago

Hi Bram, doesn't seem to work when I tried it. Could you give me an example?

Bram Stoker Over a year ago

Well, it looks like you have Expense objects or something in your list (I cannot tell from the code). Inside the class initialize the expenseAmount property to hold a default value, like "0" or something.

anonymous23 Over a year ago

Thanks for your comment, Bram. I've fixed the solution. If you'd like, you can look at the other comment for my solution.

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