异常处理RSelenium switchToFrame（）错误：ElementNotVisible

Question

我正在尝试在RSelenium中实现异常处理，并需要帮助。请注意，我已使用robotstxt包检查了抓取此页面的权限。

library(RSelenium)
library(XML)
library(janitor)
library(lubridate)
library(magrittr)
library(dplyr)

remDr <- remoteDriver(
  remoteServerAddr = "192.168.99.100",
  port = 4445L
)
remDr$open()

# Open TightVNC to follow along as RSelenium drives the browser

# navigate to the main page
remDr$navigate("https://docs.google.com/spreadsheets/d/1o1PlLIQS8v-XSuEz1eqZB80kcJk9xg5lsbueB7mTg1U/pub?output=html&widget=true#gid=690408156")

# look for table element
tableElem <- remDr$findElement(using = "id", "pageswitcher-content")

# switch to table
remDr$switchToFrame(tableElem)

# parse html for first table
doc <- htmlParse(remDr$getPageSource()[[1]])
table_tmp <- readHTMLTable(doc)
table_tmp <- table_tmp[[1]][-2, -1]
table_tmp <- table_tmp[-1, ]
colnames(table_tmp) <- c("team_name", "team_size", "start_time", "end_time", "total_time", "puzzels_solved")
table_tmp$city <- rep("montreal", nrow(table_tmp))
table_tmp$date <- rep(Sys.Date() - 5, nrow(table_tmp))

# switch back to the main/outer frame
remDr$switchToFrame(NULL)

# I found the elements I want to manipulate with Inspector mode in a browser
webElems <- remDr$findElements(using = "css", ".switcherItem") # Month/Year tabs at the bottom
arrowElems <- remDr$findElements(using = "css", ".switcherArrows") # Arrows to scroll left and right at the bottom

# Create NULL object to be used in for loop
big_df <- NULL
for (i in seq(length(webElems))) {

  # choose the i'th Month/Year tab
  webElem <- webElems[[i]]
  webElem$clickElement()

  tableElem <- remDr$findElement(using = "id", "pageswitcher-content") # The inner table frame

  # switch to table frame
  remDr$switchToFrame(tableElem)
  Sys.sleep(3)
  # parse html with XML package
  doc <- htmlParse(remDr$getPageSource()[[1]])
  Sys.sleep(3)
  # Extract data from HTML table in HTML document
  table_tmp <- readHTMLTable(doc)
  Sys.sleep(3)
  # put this into a format you can use
  table <- table_tmp[[1]][-2, -1]
  table <- table[-1, ]
  # rename the columns
  colnames(table) <- c("team_name", "team_size", "start_time", "end_time", "total_time", "puzzels_solved")
  # add city name to a column
  table$city <- rep("Montreal", nrow(table))

  # add the Month/Year this table was extracted from
  today <- Sys.Date() %m-% months(i + 1)
  table$date <- today

  # concatenate each table together
  big_df <- dplyr::bind_rows(big_df, table)

  # Switch back to main frame
  remDr$switchToFrame(NULL)

  ################################################
  ###   I should use exception handling here   ###
  ################################################


}

当浏览器到达January 2018表时，它无法再找到下一个webElems元素并抛出错误：

Selenium消息：元素当前不可见，因此可能无法与构建信息进行交互：版本：'2.53.1'，修订版：'a36b8b1'，时间：'2016-06-30 17:37:03'系统信息：主机：'617e51cbea11'，ip：'172.17.0.2'，os.name：'Linux'，os.arch：'amd64'，os.version：'4.14.79-boot2docker'，java.version：'1.8.0_91'驱动程序信息：driver.version：未知

错误：摘要：ElementNotVisible详细信息：无法完成元素命令，因为该元素在页面上不可见。 class：org.openqa.selenium.ElementNotVisibleException进一步的细节：运行errorDetails方法另外：有50个或更多警告（使用warnings（）查看前50个）

通过在for循环结束时包含这些代码，我一直在天真地处理它。这不是一个好主意，原因有两个：1）滚动速度很难找出并且会在其他（更长的）谷歌页面上失败，2）for循环最终在尝试单击右箭头时失败但最终失败它已经在最后 - 因此它不会下载最后几张表。

# click the right arrow to scroll right
arrowElem <- arrowElems[[1]]
# once you "click"" the element it is "held down" - no way to " unclick" to prevent it from scrolling too far
# I currently make sure it only scrolls a short distance - via Sys.sleep() before switching to outer frame
arrowElem$clickElement()
# give it "just enough time" to scroll right
Sys.sleep(0.3)
# switch back to outer frame to re-start the loop
remDr$switchToFrame(NULL)

我希望发生的是当弹出此错误时执行arrowElem$clickElement()来处理此异常。我想通常会使用tryCatch();然而，这也是我第一次学习异常处理。我想我可以将它包含在for循环的remDr$switchToFrame(tableElem)部分中，但它不起作用：

tryCatch({
        suppressMessages({
            remDr$switchToFrame(tableElem)
        })
    },
    error = function(e) {
        arrowElem <- arrowElems[[1]]
        arrowElem$clickElement()
        Sys.sleep(0.3)
        remDr$switchToFrame(NULL)
    }
)

异常处理RSelenium switchToFrame（）错误：ElementNotVisible

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