应用程序启动时闪亮的observeEvent触发器

Question

I have an app with observeEvent that triggers when the app starts, it doesn't wait for the button to be clicked. In this example it doesn't appear to have a difference but in my real app it causes the busyIndicator to show twice on the initial load.

name<-sample(c('a','b','c'),replace=T,5)
LAT<-runif(5,min=-26, max=-22)
LONG<-runif(5,min=-54, max=-48)
data<-data.frame(name,LAT,LONG)

ui <- shinyUI(fluidPage(
  selectInput('muni',label='Select city',
              choices=c('Show all',sort(levels(data$name)),selected=NULL)),
  htmlOutput('box'),
  leafletOutput('map')
  ))

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

data1<-reactive({
       if (input$muni!='Show all') {
           data<-data[which(data$name==input$muni),]
           }
       return(data)
})

output$box <- renderUI({

data<-data1()
num<-as.integer(nrow(data))

lapply(1:num, function(i) {
       bt <- paste0('go_btn',i)
       fluidRow(
                HTML(paste0('<div style="border: 1px solid #00000026; 
                border-radius: 10px; padding: 10px;">
                <span style="font-size:14px font-weight:bold;">',
                data$name[i],' - areas: a1, a2, a3</span></br>',
                actionButton(bt,'See map',icon=icon('map-marker',lib='font-awesome')),
                HTML('</div></br>')
                )))
       })
    })

output$map<-renderLeaflet({

data<-data1()
rownames(data)<-seq(1:nrow(data))

leaflet(data) %>%
  addProviderTiles("Esri.WorldTopoMap") %>% 
  setView(-51.5,-24.8,zoom=7) %>% 
  addMarkers(lng=~data$LONG,lat=~data$LAT)

})

lapply(1:nrow(data), function(i) {
       observeEvent(input[[paste0('go_btn',i)]], {
                    data<-data1()
                    rownames(data)<-seq(1:nrow(data))

                    leafletProxy('map',data=data,session=session) %>%
                                 clearMarkers() %>%
                                 setView(data$LONG[i],data$LAT[i],zoom=15) %>%
                                 addMarkers(lng=data$LONG[i],lat=data$LAT[i])
        },ignoreInit = T)
     })
   }

  shinyApp(ui, server)

Using options(shiny.trace = TRUE) I see that the process runs twice: SEND {"busy":"busy"} SEND {"busy":"idle"}. Can anyone tell me why my app is having this behavior?

Answer 1

I couldn't run your example so I made my own:

library(shiny)

options(shiny.trace = TRUE)

ui <- shinyUI(fluidPage(
  uiOutput("content")
))

server <- function (input, output, session) {
  output$content <- renderUI({
    actionButton("btn", "Button")
  })

  observeEvent(input$btn, {
    print("btn")
  })
}

shinyApp(ui, server)

The console output for this is:

SEND {"config":{"workerId":"","sessionId":"1ceb44576d353c33bdc92e1eebba7ad0","user":null}}
RECV {"method":"init","data":{".clientdata_output_content_hidden":false,".clientdata_pixelratio":1,".clientdata_url_protocol":"http:",".clientdata_url_hostname":"127.0.0.1",".clientdata_url_port":"5326",".clientdata_url_pathname":"/",".clientdata_url_search":"",".clientdata_url_hash_initial":"",".clientdata_url_hash":"",".clientdata_singletons":"",".clientdata_allowDataUriScheme":true}}
SEND {"busy":"busy"}
SEND {"recalculating":{"name":"content","status":"recalculating"}}
SEND {"recalculating":{"name":"content","status":"recalculated"}}
SEND {"busy":"idle"}
SEND {"errors":[],"values":{"content":{"html":"<button id=\"btn\" type=\"button\" class=\"btn btn-default action-button\">Button<\/button>","deps":[]}},"inputMessages":[]}
RECV {"method":"update","data":{"btn:shiny.action":0}}
SEND {"busy":"busy"}
SEND {"busy":"idle"}

There are two "busy" messages. The first is from observeEvent executing its eventExpr (which is NULL at this time, so it doesn't execute handlerExpr ). It always runs to check eventExpr even if ignoreInit = TRUE . The second busy comes from the initial rendering of dynamic UI.