CreditCardEditText

CreditCardEditText.java

package org.andydyer.example;

import android.content.Context;
import android.text.Editable;
import android.text.InputFilter;
import android.text.TextWatcher;
import android.util.AttributeSet;
import android.widget.EditText;


/**
 * An {@link android.widget.EditText} that applies an input mask for credit card numbers
 * 
 * Based on http://stackoverflow.com/a/12300091/3704431 with added logic for formatting
 * different card types and enforcing the appropriate max length.
 */
public class CreditCardEditText extends EditText {

    private static final String REGEX_AMEX_PREFIX = "^3[47].*";
    private static final String REGEX_DINERS_CLUB_PREFIX = "^30[0-5].*";
    private static final int CARD_TYPE_AMEX = 0;
    private static final int CARD_TYPE_DINERS_CLUB = 1;
    private static final int CARD_TYPE_OTHER = 2;

    private int cardType;

    public CreditCardEditText(Context context) {
        this(context, null);
    }

    public CreditCardEditText(Context context, AttributeSet attrs) {
        super(context, attrs);
        addTextChangedListener(textChangedListener);
    }

    /**
     * Same as setText(), but removes the TextWatcher before and restores it after
     * @param charSequence
     */
    public void setTextUnwatched(CharSequence charSequence) {
        removeTextChangedListener(textChangedListener);
        setText(charSequence);
        addTextChangedListener(textChangedListener);
    }

    private TextWatcher textChangedListener = new TextWatcher() {
        private boolean spaceDeleted;

        public void onTextChanged(CharSequence s, int start, int before, int count) {
        }

        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            // check if a space was deleted
            CharSequence charDeleted = s.subSequence(start, start + count);
            spaceDeleted = " ".equals(charDeleted.toString());
        }

        public void afterTextChanged(Editable editable) {
            removeTextChangedListener(this);

            cardType = getCardType(editable.toString());

            // record cursor position as setting the text places the cursor at the end
            int cursorPosition = getSelectionStart();
            String withSpaces = formatText(editable);
            setText(withSpaces);

            // set cursor at the last position + spaces added since spaces are added before cursor
            setSelection(cursorPosition + (withSpaces.length() - editable.length()));

            // if a space was deleted, move the cursor before the space
            if (spaceDeleted) {
                setSelection(getSelectionStart() - 1);
                spaceDeleted = false;
            }

            updateMaxLength();

            addTextChangedListener(this);
        }
    };

    private int getCardType(String number) {
        if (number.matches(REGEX_AMEX_PREFIX)) {
            return CARD_TYPE_AMEX;
        }
        if (number.matches(REGEX_DINERS_CLUB_PREFIX)) {
            return CARD_TYPE_DINERS_CLUB;
        }
        return CARD_TYPE_OTHER;
    }

    private String formatText(CharSequence text) {
        StringBuilder formatted = new StringBuilder();
        int position = 0;
        for (int i = 0; i < text.length(); i++) {
            if (Character.isDigit(text.charAt(i))) {
                if (shouldAppendSpace(position)) {
                    formatted.append(" ");
                }
                formatted.append(text.charAt(i));
                position++;
            }
        }
        return formatted.toString();
    }

    private boolean shouldAppendSpace(int position) {
        if (position == 0) {
            return false;
        }

        if (cardType == CARD_TYPE_AMEX || cardType == CARD_TYPE_DINERS_CLUB) {
            return position == 4 || position == 10;
        } else {
            return position % 4 == 0;
        }
    }

    private void updateMaxLength() {
        int maxLengthWithSpaces;
        if (cardType == CARD_TYPE_AMEX) {
            maxLengthWithSpaces = 17;
        } else if (cardType == CARD_TYPE_DINERS_CLUB) {
            maxLengthWithSpaces = 16;
        } else {
            maxLengthWithSpaces = 19;
        }

        setFilters(new InputFilter[]{ new InputFilter.LengthFilter(maxLengthWithSpaces) });
    }
}