使用下一个选项卡在 R Shiny 上显示文件

Question

我有一组图像，我想通过下一步操作按钮使用 R shiny 查看这些图像。如何使用下一步按钮一个接一个地查看它们。每次我运行我的代码时，我都可以查看第一张图片，但是，当我单击下一步按钮时，我会收到以下错误：警告：$: 对象类型 [=15 中的错误=] 不可子集化。 这是我到目前为止的代码。

library(shiny)
library(shinydashboard)

dir_path <- '*/*'
L <- list.files(dir_path, pattern = ".png")

ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(),
  dashboardBody(
    # Boxes need to be put in a row (or column)
    fluidRow(
      box(
        title = "Controls", solidHeader = TRUE, status="primary",collapsible = TRUE,
        actionButton("next_image","next")
      ),
      box(
        imageOutput("myimage",width=300,height=300)
      )
    )

  )
)

server <- function(input, output) {

  values<-reactiveValues(data = NULL)
  values$count <- 1


  ntext <- eventReactive(input$next_image,{

    # Check if the counter `values$count` are not equal to the length of your questions
    # if not then increment by 1 and return that image
    # Note that initially the button hasn't been pressed yet so the `ntext()` will not be executed
    if(values$count != length(L)){
      values$count <- values$count + 1
      return(L[values$count])
    }
    else{
      # otherwise just return the last image
      return(L[1])
    }
  })

  ntext <- eventReactive(input$next_image,{

    # Check if the counter `values$count` are not equal to the length of your questions
    # if not then increment  by 1 and return that image
    # Note that initially the button hasn't been pressed yet so the `ntext()` will not be executed
    if(values$count != length(L)){
      values$count <- values$count + 1
      print(values$count)
      return(renderImage({
          path<-file.path(paste( '*/*',L[values$count], sep = ""))

          return(list(src = path, 
                      contentType = "image/png"))
      },
      deleteFile = FALSE
      ))
    }
    else{
      # otherwise just return the last image
      return(L[length(L)])
    }
  })
  output$myimage<- renderImage({
    if (input$next_image == 0){
    path<-file.path(paste( dir_path,L[1], sep = ""))

    return(list(src = path, 
                contentType = "image/png"))} 

    ntext()
  },
  deleteFile = FALSE
  )

}

shinyApp(ui, server)

Answer 1

首先，我建议创建三个示例图片以使代码完全可重现：（它们将保存在工作目录中）

# Create 3 sample pictures
for(nr in 1:3){
  png(filename = paste0(nr, ".png"))
  plot(nr)
  dev.off()
}

你的服务器功能好像有点复杂。其实你只需要：

server <- function(input, output) {

  values <- reactiveValues(count = 1)

  observeEvent(input$next_image,{
      values$count <- min(values$count + 1, length(L))
  })

  output$plot3 <- renderImage({
    list(src = normalizePath(paste0(values$count, ".png")))
  }, deleteFile = FALSE)

}

（请注意，我假设您的工作目录中没有保存其他 .png。）

有关可用的应用，请参见下文：

# Create 3 sample pictures
for(nr in 1:3){
  png(filename = paste0(nr, ".png"))
  plot(nr)
  dev.off()
}
L <- list.files(getwd(), pattern = ".png")

library(shiny)
library(shinydashboard)
ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(),
  dashboardBody(
    # Boxes need to be put in a row (or column)
    fluidRow(
      box(
        title = "Controls", solidHeader = TRUE, status="primary",collapsible = TRUE,
        actionButton("next_image","next")
      ),
      box(
        imageOutput("plot3",width=300,height=300)
      )
    )

  )
)

server <- function(input, output) {

  values <- reactiveValues(count = 1)

  observeEvent(input$next_image,{
      values$count <- min(values$count + 1, length(L))
  })

  output$plot3 <- renderImage({
    list(src = normalizePath(paste0(values$count, ".png")))
  }, deleteFile = FALSE)
}

shinyApp(ui, server)

使用下一个选项卡在 R Shiny 上显示文件

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