R Shiny - observeEvent 不拾取清除 selectInput 事件

Question

我不确定我在这里是否遗漏了什么，当 selectInput（multi-select on）被清除时，似乎事件没有被 observeEvent 捕获。但是，它是使用 reactive() 捕获的。

请参阅下面的示例，目标是随着 select 输入的任何更改，程序将获取更改并显示在屏幕上。我使用了 2 个示例：

无法在 html_component2
ReactiveValues 使用 observeEvent 在 html_component

对于反应函数，它工作得很好。对于后者，它适用于所有组合，除非 if user unselect everything。我真的很困惑为什么，以前有没有人见过这个问题，是否有任何解决方法？在这种情况下，我更愿意为我的应用程序使用反应值。

library(shiny)

# Define UI for application that draws a histogram
ui <- fluidPage(

    # Application title
    titlePanel("Old Faithful Geyser Data"),

    # Sidebar with a slider input for number of bins 
    sidebarLayout(
        sidebarPanel(
          selectInput("sinput", "select here", c(1,2,3,4,5), multiple = T),
        ),

        # Show a plot of the generated distribution
        mainPanel(
          htmlOutput("html_component"),
          htmlOutput("html_component2"),
        )
    )
)

# Define server logic required to draw a histogram
server <- function(input, output) {
    
    rv <- reactiveValues()
    
    sel <- reactive({
      input$sinput
    })
    
    observeEvent(input$sinput, {
      rv$selected = input$sinput
    })
    
    
    output$html_component <- renderUI({
      HTML(paste(c("1:", rv$selected)))
    })
    
    output$html_component2 <- renderUI({
      HTML(paste(c("2:", sel())))
    })
}

# Run the application 
shinyApp(ui = ui, server = server)

Answer 1

默认observeEvent会忽略eventExpr中的NULL，需要设置ignoreNULL = FALSE:

library(shiny)

# Define UI for application that draws a histogram
ui <- fluidPage(
  
  # Application title
  titlePanel("Old Faithful Geyser Data"),
  
  # Sidebar with a slider input for number of bins 
  sidebarLayout(
    sidebarPanel(
      selectInput("sinput", "select here", c(1,2,3,4,5), multiple = T),
    ),
    
    # Show a plot of the generated distribution
    mainPanel(
      htmlOutput("html_component"),
      htmlOutput("html_component2"),
    )
  )
)

# Define server logic required to draw a histogram
server <- function(input, output) {
  
  rv <- reactiveValues()
  
  sel <- reactive({
    input$sinput
  })
  
  observeEvent(input$sinput, {
    rv$selected = input$sinput
  }, ignoreNULL = FALSE)
  
  output$html_component <- renderUI({
    HTML(paste(c("1:", rv$selected)))
  })
  
  output$html_component2 <- renderUI({
    HTML(paste(c("2:", sel())))
  })
}

# Run the application 
shinyApp(ui = ui, server = server)

R Shiny - observeEvent 不拾取清除 selectInput 事件

R Shiny - observeEvent do not pick up clear selectInput event

r

shiny

reactive