InputFilter on EditText cause repeating text

Question

I'm trying to implement an EditText that limits input to Capital chars only [A-Z0-9] with digits as well.

I started with the InputFilter method from some post.But here I am getting one problem on Samsung Galaxy Tab 2 but not in emulator or Nexus 4.

Problem is like this :

1. When I type "A" the text shows as "A" its good
2. Now when I type "B" so text should be "AB" but it gives me "AAB" this looks very Strange.

In short it repeats chars

Here's the code I'm working with this code :

public class DemoFilter implements InputFilter {

    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart,
            int dend) {

        if (source.equals("")) { // for backspace
            return source;
        }
        if (source.toString().matches("[a-zA-Z0-9 ]*")) // put your constraints
                                                        // here
        {
            return source.toString().toUpperCase();
        }
        return "";
    }
}

XML file code :

<EditText
    android:id="@+id/et_licence_plate_1"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_weight="3"
    android:hint="0"
    android:imeOptions="actionNext"
    android:inputType="textNoSuggestions"
    android:maxLength="3"
    android:singleLine="true"
    android:textSize="18px" >
</EditText>

I'm totally stuck up on this one, so any help here would be greatly appreciated.

Answer 1

try this:

class CustomInputFilter implements InputFilter {
    StringBuilder sb = new StringBuilder();

    @Override
    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
        Log.d(TAG, "filter " + source + " " + start + " " + end + " dest " + dest + " " + dstart + " " + dend);
        sb.setLength(0);
        for (int i = start; i < end; i++) {
            char c = source.charAt(i);
            if (Character.isUpperCase(c) || Character.isDigit(c) || c == ' ') {
                sb.append(c);
            } else
            if (Character.isLowerCase(c)) {
                sb.append(Character.toUpperCase(c));
            }
        }
        return sb;
    }
}

this also allows filtering when filter() method accepts multiple characters at once e.g. pasted text from a clipboard

Answer 2

recently i faced same problem reason of the problem is... if there is a no change in the input string then don't return source string return null, some device doesn't handle this properly that's why characters are repating.

in your code you are returning

return source.toString().toUpperCase();

don't return this , return null; in place of return source.toString().toUpperCase(); , but it will be a patch fix , it will not handle all scenarios , for all scenario you can use this code.

public class SpecialCharacterInputFilter implements InputFilter {

    private static final String PATTERN = "[^A-Za-z0-9]";
    // if you want to allow space use this pattern
    //private static final String PATTERN = "[^A-Za-z\\s]";

    @Override
    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
        // Only keep characters that are letters and digits
        String str = source.toString();
        str = str.replaceAll(PATTERN, AppConstants.EMPTY_STRING);
        return str.length() == source.length() ? null : str;
    }
}

what is happening in this code , there is a regular expression by this we will find all characters except alphabets and digits , now it will replace all characters with empty string, then remaining string will have alphabets and digits.

Answer 3

The following solution also supports the option of an autocomplete keyboard

editTextFreeNote.addTextChangedListener( new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            String newStr = s.toString();
            newStr = newStr.replaceAll( "[a-zA-Z0-9 ]*", "" );
            if(!s.toString().equals( newStr )) {
                editTextFreeNote.setText( newStr );
                editTextFreeNote.setSelection(editTextFreeNote.getText().length());
            }
        }

        @Override
        public void afterTextChanged(Editable s) {}
    } );

Answer 4

I have found many bugs in the Android's InputFilter, I am not sure if those are bugs or intended to be so. But definitely it did not meet my requirements. So I chose to use TextWatcher instead of InputFilter

private String newStr = "";

myEditText.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            // Do nothing
        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            String str = s.toString();
            if (str.isEmpty()) {
                myEditText.append(newStr);
                newStr = "";
            } else if (!str.equals(newStr)) {
                // Replace the regex as per requirement
                newStr = str.replaceAll("[^A-Z0-9]", "");
                myEditText.setText("");
            }
        }

        @Override
        public void afterTextChanged(Editable s) {
            // Do nothing
        }
    });

The above code does not allow users to type any special symbol into your EditText. Only capital alphanumeric characters are allowed.

Answer 5

The problem of characters duplication comes from InputFilter bad implementation. Rather return null if replacement should not change:

@Override
public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
    boolean keepOriginal = true;
    StringBuilder sb = new StringBuilder(end - start);
    for (int i = start; i < end; i++) {
        char c = source.charAt(i);
        if (isCharAllowed(c)) // put your condition here
            sb.append(c);
        else
            keepOriginal = false;
    }
    if (keepOriginal)
        return null;
    else {
        if (source instanceof Spanned) {
            SpannableString sp = new SpannableString(sb);
            TextUtils.copySpansFrom((Spanned) source, start, end, null, sp, 0);
            return sp;
        } else {
            return sb;
        }           
    }
}

private boolean isCharAllowed(char c) {
    return Character.isUpperCase(c) || Character.isDigit(c);
}

Answer 6

I've run into the same issue, after fixing it with solutions posted here there was still a remaining issue with keyboards with autocomplete. One solution is to set the inputType as 'visiblePassword' but that's reducing functionality isn't it?

I was able to fix the solution by, when returning a non-null result in the filter() method, use the call

TextUtils.copySpansFrom((Spanned) source, start, newString.length(), null, newString, 0);

This copies the auto-complete spans into the new result and fixes the weird behaviour of repetition when selecting autocomplete suggestions.