Understanding why action buttons in Shiny don't work, when using several of them

问题

Why when I put together several action button codes from Shiny manual (https://shiny.rstudio.com/articles/action-buttons.html), it DOES NOT run (i.e. no button reacts) ? Each code separately runs fine. How to fix it? (This is relates to this post: Convert Shiny App R code to Rmarkdown Shiny App code: with observeEvent and eventReactive)

# Code from https://shiny.rstudio.com/articles/action-buttons.html

library(shiny)

ui <- fluidPage(
  # Pattern 1 - Command
  tags$head(tags$script(src = "message-handler.js")),
  actionButton("do", "Click Me"),
  hr(),

  # Pattern 2 - Delay reactions
  actionButton("go", "Go"),
  numericInput("n", "n", 50),
  plotOutput("plot2"), 
  hr(),

  # Pattern 4 - Reset buttons
  actionButton("runif", "Uniform"),
  actionButton("reset", "Clear"),
  plotOutput("plot4")
  
)

server <- function(input, output, session) {
  
  # Pattern 1 - Command
  observeEvent(input$do, {
    session$sendCustomMessage(type = 'testmessage',
                              message = 'Thank you for clicking')
  })

  # Pattern 2 - Delay reactions
  randomVals <- eventReactive(input$go, {
    runif(input$n)
  })
  output$plot2 <- renderPlot({
    hist(randomVals())
  })
  
  # Pattern 4 - Reset buttons
  v <- reactiveValues(data = NULL)
  observeEvent(input$runif, {
    v$data <- runif(100)
  })
  observeEvent(input$reset, {
    v$data <- NULL
  })
  output$plot4 <- renderPlot({
    if (is.null(v$data)) return()
    hist(v$data)
  })
}

shinyApp(ui, server)

UPDATE:

In the original question I had output$plot in patterns 2 and 4 examples. Now these have been replaced to output$plot2 and output$plot4 - This partially resolved the problem. - Buttons for patterns 2 and 4 work now. However, Pattern 1 is still NOT working.

回答1:

As suggested you cannot have two outputs with same ID. Try this

library(shiny)

ui <- fluidPage(
  # Pattern 1 - Command
  #tags$head(tags$script(src = "message-handler.js")),
  actionButton("do", "Click Me"),
  hr(),
  
  # Pattern 2 - Delay reactions
  actionButton("go", "Go"),
  numericInput("n", "n", 50),
  #plotOutput("plot"), 
  #hr(),
  
  # Pattern 4 - Reset buttons
  actionButton("runif", "Uniform"),
  actionButton("reset", "Clear"),
  plotOutput("plot")
  
)

server <- function(input, output, session) {
  
  # Pattern 1 - Command
  observeEvent(input$do, {
    # session$sendCustomMessage(type = 'testmessage',
    #                           message = 'Thank you for clicking')
    print('Thank you for clicking')
  })
  
  ### Pattern 2 - Delay reactions
  randomVals <- eventReactive(input$go, {
    runif(input$n)
  })
  
  ### Pattern 4 - Reset buttons
  v <- reactiveValues(data = NULL)
  observeEvent(input$runif, {
    v$data <- runif(100)
  })
  observeEvent(input$go, {
    v$data <- runif(input$n)
  })
  observeEvent(input$reset, {
    v$data <- NULL
  })
  output$plot <- renderPlot({
    if (is.null(v$data)) {
      return()
    }else {
      hist(v$data)
    }

  })
}

shinyApp(ui, server)

来源：https://stackoverflow.com/questions/65671195/understanding-why-action-buttons-in-shiny-dont-work-when-using-several-of-them