How to use InputConnectionWrapper?

I have an EditText. Now I want to get all changes made by the user to this EditText and work with them before manually inserting them into the EditText. I don't want the user to directly change the text in the EditText. This should only be done by my code (e.g. by using replace() or setText()).

I searched a bit and found an interesting class named InputConnectionWrapper. According to the javadoc it shall act as a proxy for a given InputConnection. So I subclassed it like this:

private class EditTextInputConnection extends InputConnectionWrapper {

    public EditTextInputConnection(InputConnection target, boolean mutable) {
        super(target, mutable);
    }

    @Override
    public boolean commitText(CharSequence text, int newCursorPosition) {
                    // some code which takes the input and manipulates it and calls editText.getText().replace() afterwards
        return true;
    }

}

To initialize the wrapper I overwrote the following method in my EditText-subclass:

public InputConnection onCreateInputConnection(EditorInfo outAttrs) {
    InputConnection con = super.onCreateInputConnection(outAttrs);
    EditTextInputConnection connectionWrapper = new EditTextInputConnection(con, true);
    return connectionWrapper;
}

However, commitText() never gets called. The onCreateInputConnection() gets called and the constructor of EditTextInputConnection also, but never commitText(), altough it should be, when I enter some text into the field. At least, that's how I understand the usage of InputConnectionWrapper. Or am I wrong?

Edit: It seems, that commitText() is only called for special characters like "."," " etc. As I understand the Android sourcecode for all other characters InputConnectionWrapper.sendKeyEvent() should be called, but that's not the case... I'm absolutely stuck at this point. I already tried EditText.onKeyPreIme(), but this only works on hardware keyboards. So that's no alternative... I don't really understand, why Android handles soft keyboards that different from hardware keyboards. EditText.onTextChanged() gets also fired on non-user input, so this is also not, what I'm looking for.