TextWatcher events are being fired multiple times

boolean isOnTextChanged = false;

@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}

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

@Override
public void afterTextChanged(Editable quantity) {
    if (isOnTextChanged) {
        isOnTextChanged = false;
       //dosomething
    }

According to the developer pages for TextWatcher, if a change is made to the Editable within TextWatcher, it will trigger further calls to all the TextWatchers linked to that Editable. Now, clearly your code doesn't trigger this behaviour.

However, it is quite possible that if, for whatever reason, the system has a TextWatcher on the Editable, the situation you describe can occur. "Why", I hear you cry, "should this happen?"

First, the classic defence: there is no reason for it not to happen and, strictly, app code should be written to be resilient to it.

Second, I can't prove it, but I could well imagine that the code which handles layout of the displayed text within an EditText uses a TextWatcher to handle updating the display of the text on the screen. This code might insert control codes (which you aren't shown) into the Editable to ensure good line breaks and so on. It may even go round a loop a few times to get it right, and you might only get your first call after it has done all of its ...

EDIT

As per the comment by @Learn OpenGL ES, calling of a TextWatcher would be normal for things like autocorrect.

u can use a boolean check, like:

    inputBoxNumberEt.addTextChangedListener(new TextWatcher() {

        boolean ignoreChange = false;

        @Override
        public void afterTextChanged(Editable s) {
        }

        @Override
        public void beforeTextChanged(CharSequence s, int start,
                                      int count, int after) {
        }

        @Override
        public void onTextChanged(CharSequence s, int start,
                                  int before, int count) {
            if (!ignoreChange) {
              ///Do your checks                    
                ignoreChange = true;
                inputBoxNumberEt.setText(string);
                inputBoxNumberEt.setSelection(inputBoxNumberEt.getText().length());
                ignoreChange = false;
            }
        }
    });

I had the same kind of problem, when I pressed backspace with cursor at the end of a continuous text, afterTextChange was called 3 times: - The first time with the correct s value - The second time with a clear value - The third time with the correct value again

After having search a lot on the web, I tried to change my EditText inputType to

android:inputType="textNoSuggestions"

Don't ask me why, but it worked, afterTextChanged is now called only once.