private void notifyOnSoftKeyboardClosed() {
        for (SoftKeyboardStateListener listener : listeners) {
            if (listener != null) {
                listener.onSoftKeyboardClosed();
            }
        }
    }
Default value is zero (0)

@return last saved keyboard height in px
app/src/main/java/com/zhao/myreader/util/SoftKeyBroadManager.java