在R上显示文件使用下一个选项卡闪亮

Question

我有一组图像，我想通过下一个操作按钮使用R闪烁来查看。我如何使用下一个按钮一个接一个地查看它们。每次运行我的代码时，我都可以查看第一张图像，但是当我单击下一个按钮时，出现以下错误：警告：'closure'类型的$：object中的错误不可子集化。以下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

所有我建议创建三个样品图片，以使代码完全可再现的第一：（他们将被保存在工作目录中）

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

你的服务器功能似乎有点复杂。其实你需要的是：

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，我这里假设你没有其他巴纽保存在您的工作目录。）

对于工作程序见下文：

# 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)