logback-android/src/main/java/ch/qos/logback/classic/Logger.java
public synchronized void addAppender(Appender<ILoggingEvent> newAppender) {
    if (aai == null) {
      aai = new AppenderAttachableImpl<ILoggingEvent>();
    }
    aai.addAppender(newAppender);
  }
public synchronized void addAppender(Appender<ILoggingEvent> newAppender) {
    if (aai == null) {
      aai = new AppenderAttachableImpl<ILoggingEvent>();
    }
    aai.addAppender(newAppender);
  }
details.