public static int println(int priority, String tag, String msg) {
    int ret = 0;
    if (keepOriginLog) {
      ret = android.util.Log.println(priority, tag, msg);
    }
    if (output != null) {
      output.println(priority, tag, msg);
    }
    return ret;
  }
Intercept the origin log logged by {@link android.util.Log}, and pass it to specific {@link Printer}.
xlog-libcat/src/main/java/com/elvishew/xlog/libcat/internal/Cat.java