How to format number in android EditText after realtime editing-ThrowExceptions

Exception or error:

I have an EditText in which the user should input a number including decimals and i want a thousand separator automatically added onto the input number I tried a couple of other methods but some do not allow floating point numbers so i came up with this code which works well only that the string input is not being edited in realtime to one with possible thousand separators and the errors seem to stem from the s.replace();

    am2 = new TextWatcher(){
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
    }
    public void onTextChanged(CharSequence s, int start, int before, int count) {}
    public void afterTextChanged(Editable s) {
        if (s.toString().equals("")) {
            amount.setText("");
            value = 0;
        }else{
            StringBuffer strBuff = new StringBuffer();
            char c;
            for (int i = 0; i < amount2.getText().toString().length() ; i++) {
                c = amount2.getText().toString().charAt(i);
                if (Character.isDigit(c)) {
                    strBuff.append(c);
                }
            }
            value = Double.parseDouble(strBuff.toString());
            reverse();
            NumberFormat nf2 = NumberFormat.getInstance(Locale.ENGLISH);
            ((DecimalFormat)nf2).applyPattern("###,###.#######");
            s.replace(0, s.length(), nf2.format(value));
        }
    }
};
How to solve:

This Class solves the problem, allows decimal input and adds the thousand separators.

    public class NumberTextWatcher implements TextWatcher {

    private DecimalFormat df;
    private DecimalFormat dfnd;
    private boolean hasFractionalPart;

    private EditText et;

    public NumberTextWatcher(EditText et)
    {
        df = new DecimalFormat("#,###.##");
        df.setDecimalSeparatorAlwaysShown(true);
        dfnd = new DecimalFormat("#,###");
        this.et = et;
        hasFractionalPart = false;
    }

    @SuppressWarnings("unused")
    private static final String TAG = "NumberTextWatcher";

    public void afterTextChanged(Editable s)
    {
        et.removeTextChangedListener(this);

        try {
            int inilen, endlen;
            inilen = et.getText().length();

            String v = s.toString().replace(String.valueOf(df.getDecimalFormatSymbols().getGroupingSeparator()), "");
            Number n = df.parse(v);
            int cp = et.getSelectionStart();
            if (hasFractionalPart) {
                et.setText(df.format(n));
            } else {
                et.setText(dfnd.format(n));
            }
            endlen = et.getText().length();
            int sel = (cp + (endlen - inilen));
            if (sel > 0 && sel <= et.getText().length()) {
                et.setSelection(sel);
            } else {
                // place cursor at the end?
                et.setSelection(et.getText().length() - 1);
            }
        } catch (NumberFormatException nfe) {
            // do nothing?
        } catch (ParseException e) {
            // do nothing?
        }

        et.addTextChangedListener(this);
    }

    public void beforeTextChanged(CharSequence s, int start, int count, int after)
    {
    }

    public void onTextChanged(CharSequence s, int start, int before, int count)
    {
        if (s.toString().contains(String.valueOf(df.getDecimalFormatSymbols().getDecimalSeparator())))
        {
            hasFractionalPart = true;
        } else {
            hasFractionalPart = false;
        }
    }

}

Source: http://blog.roshka.com/2012/08/android-edittext-with-number-format.html

###

You need to use DecimalFormat class with DecimalFormatSymbols class, check the out following method,

public static String formatAmount(int num) 
{
    DecimalFormat decimalFormat = new DecimalFormat();
    DecimalFormatSymbols decimalFormateSymbol = new DecimalFormatSymbols();
    decimalFormateSymbol.setGroupingSeparator(',');
    decimalFormat.setDecimalFormatSymbols(decimalFormateSymbol);
    return decimalFormat.format(num);
}

###

Unfortunately the code did not work as it is in the answer.

It has two problems:

  1. It does not work if the phone locale configuration uses “,” as a decimal separator.
  2. It does not work if the number has trailing zeros in the decimal part. Example 1.01.

I went crazy to fix it.
Finally I came to this code that worked well on my cell phone:

NumberTextWatcher.java

import android.text.Editable;
import android.text.TextWatcher;
import android.text.method.DigitsKeyListener;
import android.util.Log;
import android.widget.EditText;

import java.math.RoundingMode;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.ParseException;
import java.util.Locale;


public class NumberTextWatcher
        implements TextWatcher {

    private static final String TAG = "NumberTextWatcher";

    private final int numDecimals;
    private String groupingSep;
    private String decimalSep;
    private boolean nonUsFormat;
    private DecimalFormat df;
    private DecimalFormat dfnd;
    private boolean hasFractionalPart;

    private EditText et;
    private String value;


    private String replicate(char ch, int n) {
        return new String(new char[n]).replace("\0", "" + ch);
    }

    public NumberTextWatcher(EditText et, Locale locale, int numDecimals) {

        et.setKeyListener(DigitsKeyListener.getInstance("0123456789.,"));
        this.numDecimals = numDecimals;
        DecimalFormatSymbols symbols = new DecimalFormatSymbols(locale);

        char gs = symbols.getGroupingSeparator();
        char ds = symbols.getDecimalSeparator();
        groupingSep = String.valueOf(gs);
        decimalSep = String.valueOf(ds);

        String patternInt = "#,###";
        dfnd = new DecimalFormat(patternInt, symbols);

        String patternDec = patternInt + "." + replicate('#', numDecimals);
        df = new DecimalFormat(patternDec, symbols);
        df.setDecimalSeparatorAlwaysShown(true);
        df.setRoundingMode(RoundingMode.DOWN);

        this.et = et;
        hasFractionalPart = false;

        nonUsFormat = !decimalSep.equals(".");
        value = null;

    }


    @Override
    public void afterTextChanged(Editable s) {
        Log.d(TAG, "afterTextChanged");
        et.removeTextChangedListener(this);

        try {
            int inilen, endlen;
            inilen = et.getText().length();

            String v = value.replace(groupingSep, "");

            Number n = df.parse(v);

            int cp = et.getSelectionStart();
            if (hasFractionalPart) {
                int decPos = v.indexOf(decimalSep) + 1;
                int decLen = v.length() - decPos;
                if (decLen > numDecimals) {
                    v = v.substring(0, decPos + numDecimals);
                }
                int trz = countTrailingZeros(v);

                StringBuilder fmt = new StringBuilder(df.format(n));
                while (trz-- > 0) {
                    fmt.append("0");
                }
                et.setText(fmt.toString());
            } else {
                et.setText(dfnd.format(n));
            }


            endlen = et.getText().length();
            int sel = (cp + (endlen - inilen));
            if (sel > 0 && sel <= et.getText().length()) {
                et.setSelection(sel);
            } else {
                // place cursor at the end?
                et.setSelection(et.getText().length() - 1);
            }


        } catch (NumberFormatException | ParseException nfe) {
            // do nothing?
        }


        et.addTextChangedListener(this);
    }

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
        Log.d(TAG, "beforeTextChanged");
        value = et.getText().toString();
    }

    private int countTrailingZeros(String str) {
        int count = 0;

        for (int i = str.length() - 1; i >= 0; i--) {
            char ch = str.charAt(i);
            if ('0' == ch) {
                count++;
            } else {
                break;
            }
        }
        return count;
    }

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        Log.d(TAG, "onTextChanged");

        String newValue = s.toString();
        String change = newValue.substring(start, start + count);
        String prefix = value.substring(0, start);
        String suffix = value.substring(start + before);

        if (".".equals(change) && nonUsFormat) {
            change = decimalSep;
        }

        value = prefix + change + suffix;
        hasFractionalPart = value.contains(decimalSep);

        Log.d(TAG, "VALUE: " + value);


    }

}

and then to use it simply to do:

    Locale locale = new Locale("es", "AR"); // For example Argentina
    int numDecs = 2; // Let's use 2 decimals
    TextWatcher tw = new NumberTextWatcher(myEditText, locale, numDecs);
    myEditText.addTextChangedListener(tw);

###

you can use kotlin extensions function like this…

fun EditText.onCommaChange(input: (String) -> Unit) {
this.addTextChangedListener(object : TextWatcher {
    override fun afterTextChanged(s: Editable?) {
        if (!edit) {
            edit = true
            if (s.toString() != "₹") {
                try {
                    val flNumber = getCommaLessNumber(s.toString()).toInt()
                    val fNumber = getFormattedAmount(flNumber)
                    setText(fNumber)
                    setSelection(text.length)
                    input(flNumber.toString())
                } catch (e: NumberFormatException) {
                    Timber.e(e)
                }
            } else {
                setText("")
                input("")
            }
            edit = false
        }
    }

    override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {}

    override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {}
})}

fun getCommaLessNumber(commaNumber: String): String {
var number = commaNumber.replace("₹", "")
number = number.replace(",".toRegex(), "")
return number}

fun getFormattedAmount(amount: Int): String {
return "₹${String.format("%,d", amount)}"}

fun EditText.text() = this.text.toString()

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