通过闪亮的按钮动态添加/删除输入字段并保留值

Posted 2023-03-24

【中文标题】通过闪亮的按钮动态添加/删除输入字段并保留值

【英文标题】：Add/remove input fields dynamically by a button in shiny AND keep values

【发布时间】：2017-05-05 03:12:22

【问题描述】：

我的问题是以下讨论的后续问题：

How to add/remove input fields dynamically by a button in shiny

我希望能够使用闪亮应用程序上的操作按钮动态添加/删除输入，而且当我添加新输入时，我希望输入字段的值保持不变，而不是像现在一样改变。你能帮我解决这个问题吗？

例如，如果我更改第一个框并通过按钮添加另一个文本输入，则第一个框的值已重置为默认值。

library(shiny)

ui <- shinyUI(fluidPage(

  sidebarPanel(

      actionButton("add_btn", "Add Textbox"),
      actionButton("rm_btn", "Remove Textbox"),
      textOutput("counter")

    ),

  mainPanel(uiOutput("textbox_ui"))

))

server <- shinyServer(function(input, output, session) 

  # Track the number of input boxes to render
  counter <- reactiveValues(n = 0)

  observeEvent(input$add_btn, counter$n <- counter$n + 1)
  observeEvent(input$rm_btn, 
    if (counter$n > 0) counter$n <- counter$n - 1
  )

  output$counter <- renderPrint(print(counter$n))

  textboxes <- reactive(

    n <- counter$n

    if (n > 0) 
      lapply(seq_len(n), function(i) 
        textInput(inputId = paste0("textin", i),
                  label = paste0("Textbox", i), value = "Hello World!")
      )
    

  )

  output$textbox_ui <- renderUI( textboxes() )

)

shinyApp(ui, server)

【参考方案1】：

可能有更好的解决方案，但这也可以：

library(shiny)

ui <- shinyUI(fluidPage(
  
  sidebarPanel(
    actionButton("add_btn", "Add Textbox"),
    actionButton("rm_btn", "Remove Textbox"),
    textOutput("counter")
    
  ),
  
  mainPanel(uiOutput("textbox_ui"))
  
))

server <- shinyServer(function(input, output, session) 
  
  # Track the number of input boxes to render
  counter <- reactiveValues(n = 0)
  
  #Track the number of input boxes previously
  prevcount <-reactiveValues(n = 0)
  
  observeEvent(input$add_btn, 
        counter$n <- counter$n + 1
        prevcount$n <- counter$n - 1)
  
  observeEvent(input$rm_btn, 
    if (counter$n > 0) 
      counter$n <- counter$n - 1 
      prevcount$n <- counter$n + 1
    
     
  )
  
  output$counter <- renderPrint(print(counter$n))
  
  textboxes <- reactive(
    
    n <- counter$n
    
    if (n > 0) 
      # If the no. of textboxes previously where more than zero, then 
      #save the text inputs in those text boxes 
      if(prevcount$n > 0)
        
         vals = c()
        if(prevcount$n > n)
          lesscnt <- n
          isInc <- FALSE
        else
          lesscnt <- prevcount$n
          isInc <- TRUE
        
        for(i in 1:lesscnt)
          inpid = paste0("textin",i)
         vals[i] = input[[inpid]] 
        
        if(isInc)
          vals <- c(vals, "New text box")
        
        
        lapply(seq_len(n), function(i) 
          textInput(inputId = paste0("textin", i),
                    label = paste0("Textbox", i), value = vals[i])
        )
        
      else
        lapply(seq_len(n), function(i) 
          textInput(inputId = paste0("textin", i),
                    label = paste0("Textbox", i), value = "New text box")
        ) 
      
      
    
    
  )
  
  output$textbox_ui <- renderUI( textboxes() )
  
)

shinyApp(ui, server)