Validation allow only number and characters in edit text in android-ThrowExceptions

Exception or error:

In my application i have to validate the edittext. It should only allow character, digits, underscore and hypen.

Here is my code:

edittext.addTextChangedListener(new TextWatcher() {

                        @Override
                        public void onTextChanged(CharSequence s, int start, int before, int count) {
                            // TODO Auto-generated method stub

                            }

                        @Override
                        public void beforeTextChanged(CharSequence s, int start, int count,
                        int after) {
                                            // TODO Auto-generated method stub

                            }

                                        @Override
                            public void afterTextChanged(Editable s) {
                                            // validation codes here

                            location_name=s.toString();
                            Toast.makeText(getApplicationContext(),location_name, Toast.LENGTH_SHORT).show();                

                            if (location_name.matches(".*[^a-z^0-9].*")) 
                                {
                            location_name = location_name.replaceAll("[^a-z^0-9]", "");
                            s.append(location_name);
                            s.clear();
                            Toast.makeText(getApplicationContext(),"Only lowercase letters and numbers are allowed!",Toast.LENGTH_SHORT).show();

                            }

                            }

                        });     

location.add(location_name);

in this , when i entered input in edittext ,application is force closed.please give me suggestion.Thanks in advance.

How to solve:

Instead of using your “manual” checking method, there is something very easy in Android:

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)) && 
                !Character.toString(source.charAt(i)).equals("_") && 
                !Character.toString(source.charAt(i)).equals("-")) 
            { 
                return ""; 
            } 
        } 
        return null; 
    } 
}; 

edittext.setFilters(new InputFilter[] { filter }); 

Or another approach: set the allowed characters in the XML where you are creating your EditText:

<EditText 
  android:inputType="text" 
  android:digits="0,1,2,3,4,5,6,7,8,9,*,qwertzuiopasdfghjklyxcvbnm,_,-" 
  android:hint="Only letters, digits, _ and - allowed" />

###

<EditText 
  android:inputType="text" 
  android:digits="0,1,2,3,4,5,6,7,8,9,*,qwertzuiopasdfghjklyxcvbnm,_,-" 
  android:hint="Only letters, digits, _ and - allowed"
/>

the above code will also include , additionally to avoid , use the following code

<EditText 
  android:inputType="text" 
  android:digits="0123456789qwertzuiopasdfghjklyxcvbnm_-"
  android:hint="Only letters, digits, _ and - allowed"
/>

###

This can be useful, especially if your EditText should allow diacritics (in my case, Portuguese Diacritic):

<EditText
   android:digits="0123456789AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzÁáÂâÃãÀàÇçÉéÊêÍíÓóÔôÕõÚú"
/>

###

A solution similar to the android:digits="0123456789*", is to use this:

EditText etext = new EditText(this);
etext.setKeyListener(new DigitsKeyListener().getInstance("0123456789*"));

An added bonus is that it also displays the numeric keypad.

###

Try this:

public static SpannableStringBuilder getErrorMsg(String estring) {
        int ecolor = Color.BLACK; // whatever color you want
        ForegroundColorSpan fgcspan = new ForegroundColorSpan(ecolor);
        SpannableStringBuilder ssbuilder = new SpannableStringBuilder(estring);
        ssbuilder.setSpan(fgcspan, 0, estring.length(), 0);
        return ssbuilder;
    }

Then setError() to EditText when you want show ‘only Letters and digits are allowed’ as below.

etPhone.setError(getErrorMsg("Only lowercase letters and numbers are allowed!"));

Hope this will help you. I use the same for Validation Check in EditText in my apps.

###

please try adding the android:digits=”abcde…..012345789″ attribute? although the android:digits specify that it is a numeric field it does work for me to set it to accept letters as well, and special characters as well (tested on SDK-7)

###

use this 2 function

public static boolean isdigit(EditText input)
    {

    String data=input.getText().toString().trim();
    for(int i=0;i<data.length();i++)
    {
         if (!Character.isDigit(data.charAt(i)))
                return false;

    }
    return true;
    }

    public static boolean ischar(EditText input)
    {

    String data=input.getText().toString().trim();
    for(int i=0;i<data.length();i++)
    {
         if (!Character.isDigit(data.charAt(i)))
                return true;

    }
    return false;
    }

pass Edittext variable in these function .. so you can have boolean value.

###

You can validate this by two ways , both worked for me, hope will be helpful for you too.

1> Mentioning the chars in your edittext .

android:digits="0,1,2,3,4,5,6,7,8,9,*,qwertzuiopasdfghjklyxcvbnm,_,-" 

2> Can validate pragmatically as answered by milos pragmatically

###

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.toString(source.charAt(i)).matches("[a-zA-Z0-9-_]+")) {
                return "";
                edittext.seterror("Only letters, digits, _ and - allowed");
            }
        }
        return null;
    }
};
edittext.setFilters(new InputFilter[] { filter });

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