How to restrict TextView to allow only alpha-numeric characters in Android

In the XML, put this:

android:digits="abcdefghijklmnopqrstuvwxyz1234567890 "

Here is a better solution......... https://groups.google.com/forum/?fromgroups=#!topic/android-developers/hS9Xj3zFwZA

InputFilter filter = new InputFilter() {         public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {                 for (int i = start; i < end; i++) {                         if (!Character.isLetterOrDigit(source.charAt(i))) {                                 return "";                         }                 }                 return null;         } }; edit.setFilters(new InputFilter[]{filter});

The InputFilter solution works well, and gives you full control to filter out input at a finer grain level than android:digits. The filter() method should return null if all characters are valid, or a CharSequence of only the valid characters if some characters are invalid. If multiple characters are copied and pasted in, and some are invalid, only the valid characters should be kept (@AchJ's solution will reject the entire paste if any characters a invalid).

public static class AlphaNumericInputFilter implements InputFilter {    public CharSequence filter(CharSequence source, int start, int end,            Spanned dest, int dstart, int dend) {        // Only keep characters that are alphanumeric        StringBuilder builder = new StringBuilder();        for (int i = start; i < end; i++) {            char c = source.charAt(i);            if (Character.isLetterOrDigit(c)) {                builder.append(c);            }        }        // If all characters are valid, return null, otherwise only return the filtered characters        boolean allCharactersValid = (builder.length() == end - start);        return allCharactersValid ? null : builder.toString();    }}

Also, when setting your InputFilter, you must make sure not to overwrite other InputFilters set on your EditText; these could be set in XML, like android:maxLength. You must also consider the order that the InputFilters are set. When used in conjunction with a length filter, your custom filter should be inserted before the length filter, that way pasted text applies the custom filter before the length filter (@AchJ's solution will overwrite all other InputFilters and only apply the custom one).

    // Apply the filters to control the input (alphanumeric)    ArrayList<InputFilter> curInputFilters = new ArrayList<InputFilter>(Arrays.asList(editText.getFilters()));    curInputFilters.add(0, new AlphaNumericInputFilter());    InputFilter[] newInputFilters = curInputFilters.toArray(new InputFilter[curInputFilters.size()]);    editText.setFilters(newInputFilters);