logback-android/src/main/java/ch/qos/logback/core/spi/AppenderAttachableImpl.java
public boolean isAttached(Appender<E> appender) {
    if (appender == null) {
      return false;
    }
    for (Appender<E> a : appenderList) {
      if (a == appender) return true;
    }
    return false;
  }
public boolean isAttached(Appender<E> appender) {
    if (appender == null) {
      return false;
    }
    for (Appender<E> a : appenderList) {
      if (a == appender) return true;
    }
    return false;
  }
Returns <code>true</code> if the specified appender is in the list of
attached appenders, <code>false</code> otherwise.

@since 1.2