获取在 Shiny 中触发的事件？

Question

我想在下面的示例中知道在多个ObserveEvent().

ui <- fluidPage(
  numericInput("a", "a", 0),
  textInput("b", "b")
)

server <- function(input, output, session) {
  observeEvent({
    input$a
    input$b
  },{

    # If only input$a is fired, I want to know that is input$a

  })
}

shinyApp(ui, server)

或者唯一的解决方案是ObserveEvent()像第二个链接那样有两个？像那样 ？

ui <- fluidPage(
  numericInput("a", "a", 0),
  textInput("b", "b")
)

server <- function(input, output, session) {
  observeEvent({
    input$a
  },{

    my_function_or_reactive_function(input,1)

  })

  observeEvent({
    input$b
  },{

    my_function_or_reactive_function(input,2)

  })

}

shinyApp(ui, server)

关联：

• 如何在 Shiny eventReactive 处理程序中侦听多个事件表达式
• https://groups.google.com/forum/#!topic/shiny-discuss/vd_nB-BH8sw

Answer 1

您可以使用 Shiny 的JS 事件 shiny:inputchanged来检查哪个输入发生了变化：

ui <- fluidPage(
  tags$head(
    tags$script(
      "$(document).on('shiny:inputchanged', function(event) {
          if (event.name != 'changed') {
            Shiny.setInputValue('changed', event.name);
          }
        });"
    )
  ),
  numericInput("a", "a", 0),
  textInput("b", "b"),
  textInput("c", "c"),
  textOutput("changedInputs"),
  textOutput("aFired")
)

server <- function(input, output, session) {
  output$changedInputs <- renderText({
    paste("Outside observer: Latest input fired:", paste(input$changed, collapse = ", "))
  })
  
  observeEvent({
    c(input$a,
      input$b)
  }, {
    req(input$changed)
    if (input$changed == "a") {
      output$aFired <- renderText("Inside observer: input$a was fired")
    } else if (input$changed == "b") {
      output$aFired <- renderText("Inside observer: input$b was fired")
    } else if (input$changed == "c") {
      output$aFired <- renderText("Inside observer: input$c was fired")
    }
  }, ignoreInit = TRUE)
}

shinyApp(ui, server)

：

编辑- 来自@TristanTran 的请求使用renderUI：

library(shiny)

ui <- fluidPage(
  tags$head(
    tags$script(
      "$(document).on('shiny:inputchanged', function(event) {
          if (event.name != 'changed') {
            Shiny.setInputValue('changed', event.name);
          }
        });"
    )
  ),
  uiOutput("serverside"),
  textOutput("changedInputs"),
  textOutput("aFired")
)

server <- function(input, output, session) {
  output$changedInputs <- renderText({
    paste("Outside observer: Latest input fired:", paste(input$changed, collapse = ", "))
  })
  
  output$serverside <- renderUI({
    tagList(
      numericInput("a", "a", 0),
      textInput("b", "b"),
      textInput("c", "c")
    )
  })
  
  observeEvent({
    c(input$a,
      input$b)
  }, {
    req(input$changed)
    if (input$changed == "a") {
      output$aFired <- renderText("Inside observer: input$a was fired")
    } else if (input$changed == "b") {
      output$aFired <- renderText("Inside observer: input$b was fired")
    } else if (input$changed == "c") {
      output$aFired <- renderText("Inside observer: input$c was fired")
    }
  }, ignoreInit = TRUE)
}

shinyApp(ui, server)