Use this to change the hint color. -
editText.setHintTextColor(getResources().getColor(R.color.white));
Solution for your problem -
editText.addTextChangedListener(new TextWatcher() {
@Override
public void onTextChanged(CharSequence arg0, int arg1, int arg2,int arg3){
//do something
}
@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
//do something
}
@Override
public void afterTextChanged(Editable arg0) {
if(arg0.toString().length() <= 0) //check if length is equal to zero
tv.setHintTextColor(getResources().getColor(R.color.white));
}
});