EditTextOnEmptyChangedListener.java

import android.text.Editable;
import android.text.TextWatcher;

/**
 * Listen to "EmptyChange" events on an EditText.
 * <p/>
 * Created by KANGOD on 8/18/2016.
 */
public abstract class EditTextOnEmptyChangedListener implements TextWatcher {
    @Override
    public final void beforeTextChanged(CharSequence s, int start, int count, int after) {}

    @Override
    public final void onTextChanged(CharSequence s, int start, int before, int count) {
        if (s.length() == 0) {
            onEmptyChanged(true);
        } else if (start == 0 && before == 0 && s.length() == count) {
            onEmptyChanged(false);
        } // else: not an "EmptyChange" event
    }

    @Override
    public final void afterTextChanged(Editable editable) {}

    /**
     * @param isEmpty If the EditText is empty after text changed.
     */
    public abstract void onEmptyChanged(boolean isEmpty);
}

Usage.java

etAuthCode.addTextChangedListener(new EditTextOnEmptyChangedListener() {
    @Override
    public void onEmptyChanged(boolean isEmpty) {
        btnNextStep.setEnabled(!isEmpty);
    }
});