statusEdt.addTextChangedListener(new TextWatcher(){
public void afterTextChanged(Editable s) {}
public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
public void onTextChanged(CharSequence s, int start, int before, int count) {
//do stuff
charTxt.setText(statusEdt.getText().length() + "/140");
}
});
I used this TextChangedListener(TextWatcher) to keep a count of how many characters had been typed into an EditText for a Twitter client I made. You could probably use a listener like this. You'll want to override beforeTextChanged or onTextChanged. These methods will pass you whatever CharSequence has been typed. You can check what was typed in and if it is not valid input you can remove it by calling setText() and passing in whatever has been typed so far minus the invalid characters.