将EditText的值设置为其自己的值，已修改-导致冻结

Question

I'm trying to have an EditText with a number, and when the user types a number - commas will automatically be added, using a regular expression pattern.
This is what I've tried:

input.addTextChangedListener(new TextWatcher() {
...
    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        if (input.getText().toString().length() >= 4)
            input.setText(addComma(input.getText().toString()));
    }
...
}

addComma(String):

public String addComma(String number) {
    return number.replace(",", "").replaceAll("\\B(?=(\\d{3})+(?!\\d))", ",");
}

When typing a number with 4 digits - the app is freezing and crashing after a while.

Answer 1

Because you have an infinite loop in your application. When you set the text of a TextView your text changes and therefore the onTextChanged method is called again causing the text to be changed again etc. etc.

You could use some boolean value which tests wether the text is already edited and only call it when it is not just edited by your method.

Create a field in your class:

private boolean justEdited = false;

And use it in your listener:

input.addTextChangedListener(new TextWatcher() {
    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        if (input.getText().toString().length() >= 4 && !justEdited) {
            justEdited = true;
            input.setText(addComma(input.getText().toString()));
        } else if (justEdited) {
            justEdited = false;
        }
    }
}