r闪亮：按下按钮时eventReactive没有反应

Posted 2023-03-24

【中文标题】r闪亮：按下按钮时eventReactive没有反应

【英文标题】：r shiny: eventReactive is not reacting when the button is pressed

【发布时间】：2018-08-01 07:17:00

【问题描述】：

下面是我的代码。它可能看起来有点长，但实际上它是一个非常简单的应用程序。

用户应该上传一个很小的数据框（如果您在美国，则为 x.csv，如果您在欧洲，则为 x_Europe.csv）。然后用户应该点击按钮开始计算。最后，用户应该能够以数据框的形式下载这些计算的结果。

我的问题：上传文件后，当我单击“do_it”操作按钮时 - 没有任何反应。我可以看到它，因为我的控制台上没有打印任何内容。为什么？毕竟，我的函数“main_calc”应该是 eventReactive 到 input$do_it？为什么 main_calc 中的所有计算只有在用户尝试下载结果后才开始发生？

重要提示：将“数据”函数与 main_calc 分开对我来说很重要。

非常感谢！

首先，在您的工作目录中生成以下两个文件之一：

# generate file 'x.csv' to read in later in the app:
write.csv(data.frame(a = 1:4, b = 2:5), "x.csv", row.names = F)  # US file
write.csv2(data.frame(a = 1:4, b = 2:5), "x_Europe.csv", row.names = F)

这是闪亮应用的代码：

library(shiny)

ui <- fluidPage(
  # User should upload file x here:
  fileInput("file_x", label = h5("Upload file 'x.csv'!")),
  br(),
  actionButton("do_it", "Click Here First:"),
  br(),
  br(),
  textInput("user_filename","Save your file as:", value = "My file x"),
  downloadButton('file_down',"Save the output File:")
)

server <- function(input, output, session) 

  #----------------------------------------------------------------------
  # Function to read in either European (csv2) or American (csv) input:
  #----------------------------------------------------------------------

  ReadFile <- function(pathtofile, withheader = TRUE)

    test <- readLines(pathtofile, n = 1)  
    if (length(strsplit(test, split = ";")[[1]]) > 1) 
      print("Reading European CSV file")
      outlist <- list(myinput = read.csv2(pathtofile, header = TRUE),
                      europe.file = 1)
     else 
      print("Reading US CSV file")
      outlist <- list(myinput = read.csv(pathtofile, header = TRUE),
                      europe.file = 0)
    
    return(outlist)
  

  #----------------------------------------------------------------------
  # Data-related - getting the input file
  #----------------------------------------------------------------------  

  Data <- reactive(

    print("Starting reactive function 'Data'")
    # Input file:
    infile_x <- input$file_x
    myx <- ReadFile(infile_x$datapath)$myinput

    # European file?
    europe <- ReadFile(infile_x$datapath)$europe.file

    print("Finishing reactive function 'Data'")
    return(list(data = myx, europe = europe))

  )

  #----------------------------------------------------------------------
  # Main function that should read in the input and 'calculate' stuff
  # after the users clicks on the button 'do_it' - takes about 20 sec
  #----------------------------------------------------------------------

  main_calc <- eventReactive(input$do_it, 

    req(input$file_x)

    # Reading in the input file:
    x <- Data()$data
    print("Done reading in the data inside main_calc")

    # Running useless calculations - just to kill time:

    myvector <- matrix(unlist(x), ncol = 1, nrow = 1000)
    print("Starting calculations")

    for (i in seq_len(10)) 
      set.seed(12)
      mymatr <- matrix(abs(rnorm(1000000)), nrow = 1000)
      temp <- solve(mymatr) %*% myvector
    

    print("Finished calculations")

    # Creating a new file:
    y <- temp
    result = list(x = x, y = y)
    print("End of eventReactive function main_calc.")
    return(result)
  )   # end of main_calc

  #----------------------------------------------------------------------
  # The user should be able to save the output of main_calc as a csv file
  # using a string s/he specified for the file name:
  #----------------------------------------------------------------------

  output$file_down <- downloadHandler(
    filename = function() 
      paste0(input$user_filename, " ", Sys.Date(), ".csv") 
    ,
    content = function(file) 
      print("Europe Flag is:")
      print(Data()$europe)

      if (Data()$europe == 1) 
        x_out <- main_calc()$x
        print("Dimensions of x in downloadHandler are:")
        print(dim(x_out))        
        write.csv2(x_out, 
                   file,
                   row.names = FALSE)
       else 
        x_out <- main_calc()$x
        print("Dimensions of x in downloadHandler are:")
        print(dim(x_out))
        write.csv(x_out, 
                  file,
                  row.names = FALSE)
      
    
  )


  # end of server code  

shinyApp(ui, server)

【问题讨论】：

尝试将main_calc() 添加为downloadHandler 的第一行以创建依赖项

也许这个问题将有助于澄清：***.com/questions/33519816/…。 eventReactive 对象在事件发生时不会“运行”，它们只是被标记为无效。在实际向它们请求值之前，它们不会运行。因此，由于您在按下下载按钮之前不使用main_calc()，因此直到那时它才会运行。您可能希望 observeEvent 与 reactiveValues 对象进行此类交互。

有趣（也很疯狂！） - 我添加了 main_calc()，作为 downloadHandler 中的第一行。确实-在我单击按钮后进行了计算，但是：计算结束后，文件下载按钮非常小，当我单击它时，一切都崩溃了：“ self$downloads$set（name，list）中的警告(filename = filename, contentType = contentType, : 重新启动中断的 Promise 评估" 然后：运行中的错误 (timeoutMs) ：期望单个字符串值：[type=character; extent=2]。

@MrFlick 但是如果我使用 observeEvent - 我不能返回任何东西，可以吗？如果我没有返回我需要下载的对象的函数（如 main_calc），我的 downloadHandler 应该下载什么？

@user3245256 是的，你不能返回任何东西。这就是为什么您需要更新事件之外的 reactiveValues 对象中的值。看这个简单的例子：gist.github.com/aagarw30/69feeeb7e813788a753b71ef8c0877eb

【参考方案1】：

以下是解决方案 - 基于 MrFlick 的建议：

# generate file 'x.csv' to read in later in the app:
# write.csv(data.frame(a = 1:4, b = 2:5), "x.csv", row.names = F)
# write.csv2(data.frame(a = 1:4, b = 2:5), "x_Europe.csv", row.names = F)

library(shiny)
library(shinyjs)

ui <- fluidPage(
  # User should upload file x here:
  fileInput("file_x", label = h5("Upload file 'x.csv'!")),
  br(),
  actionButton("do_it", "Click Here First:"),
  br(),
  br(),
  textInput("user_filename","Save your file as:", value = "My file x"),
  downloadButton('file_down',"Save the output File:")
)

server <- function(input, output, session) 



  #----------------------------------------------------------------------
  # Function to read in either European (csv2) or American (csv) input:
  #----------------------------------------------------------------------

  ReadFile <- function(pathtofile, withheader = TRUE)

    test <- readLines(pathtofile, n = 1)  
    if (length(strsplit(test, split = ";")[[1]]) > 1) 
      print("Reading European CSV file")
      outlist <- list(myinput = read.csv2(pathtofile, header = TRUE),
                      europe.file = 1)
     else 
      print("Reading US CSV file")
      outlist <- list(myinput = read.csv(pathtofile, header = TRUE),
                      europe.file = 0)
    
    return(outlist)
  


  #----------------------------------------------------------------------
  # Data-related - getting the input file
  #----------------------------------------------------------------------  

  Data <- reactive(


    print("Starting reactive function Data")
    # Input file:
    infile_x <- input$file_x
    myx <- ReadFile(infile_x$datapath)$myinput

    # European file?
    europe <- ReadFile(infile_x$datapath)$europe.file

    print("Finishing reactive function 'Data'")
    return(list(data = myx, europe = europe))

  )

  #----------------------------------------------------------------------
  # Main function that should read in the input and 'calculate' stuff
  # after the users clicks on the button 'do_it' - takes about 20 sec
  #----------------------------------------------------------------------


  # Creating reactive Values:
  forout_reactive <- reactiveValues()

  observeEvent(input$do_it, 

    print("STARTING observeEvent")

    req(input$file_x)

    # Reading in the input file:
    x <- Data()$data
    print("Done reading in the data inside observeEvent")

    # Running useless calculations - just to kill time:

    myvector <- matrix(unlist(x), ncol = 1, nrow = 1000)
    print("Starting calculations")

    for (i in seq_len(10)) 
      set.seed(12)
      mymatr <- matrix(abs(rnorm(1000000)), nrow = 1000)
      temp <- solve(mymatr) %*% myvector
      # takes about 22 sec on a laptop

    print("Finished calculations")

    # Creating a new file:
    y <- temp
    forout_reactive$x = x
    forout_reactive$y = y
    print("End of observeEvent")
  )   # end of main_calc

  #----------------------------------------------------------------------
  # The user should be able to save the output of main_calc as a csv file
  # using a string s/he specified for the file name:
  #----------------------------------------------------------------------

  output$file_down <- downloadHandler(
    filename = function() 
      paste0(input$user_filename, " ", Sys.Date(), ".csv") 
    ,
    content = function(file) 
      print("Europe Flag is:")
      print(Data()$europe)

      if (Data()$europe == 1) 
        y_out <- forout_reactive$y
        print("Dimensions of y in downloadHandler are:")
        print(dim(y_out))        
        write.csv2(y_out, 
                   file,
                   row.names = FALSE)
       else 
        y_out <- forout_reactive$y
        print("Dimensions of y in downloadHandler are:")
        print(dim(y_out))
        write.csv(y_out, 
                  file,
                  row.names = FALSE)
      
    
  )


  # end of server code  

shinyApp(ui, server)