replace character inside TextWatcher in android

Question

i use a TextWatcher to change pressed key value. my goal is that replace some characters while typing. for example when i type keys, if reached "S" character, replaces it with "a" character. my question is: should i do it in beforeTextChanged?? how? can anyone give me an example?

try to use `afterTextChanged` instead of `beforeTextChanged` for replacing Characters in EditText — ρяσѕρєя K, Mar 27 '13 at 07:36
i tried to do this but i cant get what i want. can you give me an example? — Fcoder, Mar 27 '13 at 07:37
plz explain more what u are getting if u are using afterTextChanged and what u want to get more help — ρяσѕρєя K, Mar 27 '13 at 07:40

score 14 · Answer 1 · edited Feb 22 '17 at 17:51

14

I know that this post is a couple of years old, but both versions did not work for me and have build a hybrid between the two answers.

@Override
public void afterTextChanged(Editable editable) {    
    if (editable.toString().contains(",")) {
       Editable ab = new SpannableStringBuilder(editable.toString().replace(",", ""));
       editable.replace(0, editable.length(), ab);
    }
}

edited Feb 22 '17 at 17:51

tynn

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answered Apr 26 '16 at 08:38

quantum apps

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This is better than accepted answer since it doesn't move the cursor position to front. – 林果皞 Jan 11 '19 at 10:54
1

In my case (not checking `,`), I also need to do `editTextView.removeTextChangedListener(this);` in the first line of this method to prevent infinite call this method over and over again. – 林果皞 Jan 11 '19 at 11:06
1

It is recommended to create boolean inside custom TextWatcher to prevent infinite loop, example class from Android team: PhoneNumberFormattingTextWatcher – Darek Deoniziak Mar 20 '20 at 08:46

score 1 · Accepted Answer · edited Jun 09 '16 at 15:15

1

Using beforeTextChanged won't be useful because it won't interrupt the actual printing of the key to the EditText. I would use something similar to:

    public void afterTextChanged(Editable s) {
        if(s.length() > 0 && s.toString().charAt(s.length()-1) == 'S')
        {
            final String newText = s.toString().substring(0, s.length()-1) + "a"; 
            editText.setText(newText); 
        }
    }

I added some toString()'s, not 100% sure how Editable works but I think that should cover it.

edited Jun 09 '16 at 15:15

0xPixelfrost

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answered Mar 27 '13 at 07:36

RyPope

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"quantum apps" answer below is superior. TextWatcher shouldn't need to hold reference to editText instance, calling editText.setText from TextWatcher creates cursor problems. – Darek Deoniziak Mar 20 '20 at 08:52

score 1 · Answer 3 · answered Feb 25 '19 at 12:36

You have to do it in the afterTextChanged, but don't forget to detach and reattach the TextChangedListener to prevent an endless loop.
A simple example is shown below :

public void afterTextChanged(Editable s) {
        editText.removeTextChangedListener(this);
        //.. do changes here ..//
        editText.setText(newText);
        editText.addTextChangedListener(this);
}

But there is another problem when you call setText, it causes the cursor to move to the end of the text inside the textView. So you have to calculate the new position for the curser yourself, remember user may enter the multiple characters at once by pasting or delete a selected part of the text.
Here is a more complete example. This watcher class removes all nonnumeric characters of the text.

public class NumWatcher implements TextWatcher {
    private EditText editText;
    private int selPos;
    private String oldString, newString;
    public NumWatcher(EditText editText) {
        this.editText = editText;
    }

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
        selPos = editText.getSelectionStart();
        oldString = myFilter(s.toString());
    }

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

    @Override
    public void afterTextChanged(Editable s) {
        editText.removeTextChangedListener(this);
        newString = myFilter(s.toString());
        editText.setText(newString);
        int newPos = selPos + (newString.length() - oldString.length());
        if (newPos < 0) newPos = 0;
        editText.setSelection(newPos);
        editText.addTextChangedListener(this);
    }

    public String myFilter(String s) {
        String digits;
        digits = s.replaceAll("[^0-9]", "");
        if (s.equals("")) return "";
        return digits;
    }
}

Instead of holding reference of EditText in TextWatcher it is recommended to create boolean to prevent infinite loop. Take a look at PhoneNumberFormattingTextWatcher from Android team — Darek Deoniziak, Mar 20 '20 at 08:55

score -3 · Answer 4 · edited Mar 27 '13 at 08:52

-3

@Override
public void afterTextChanged(Editable arg0) {
    Editable ab = new SpannableStringBuilder(arg0.toString().replace("S", "a"));
    arg0 = ab ;
}

edited Mar 27 '13 at 08:52

bsiamionau

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answered Mar 27 '13 at 08:26

Mobeen Altaf

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Reassigning local variable will have no effect on the original Editable value! – user2878850 Sep 19 '17 at 19:08

replace character inside TextWatcher in android

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