downloadHandler in shiny in a loop - r

Question

I am trying to build a shiny app to retrieve data from an Oracle table based on user specified ID. I want to create one file with data for each ID and download it to the default downloads folder. I would also like to zip the files and provide the user with that one file. Also, the app is just to download the data and I really don't want a main Panel hence the width of the mainPanel is zero. If that's not the way to do it, please let me know.The app is going to reside on a server and hence the need for a download Handler. Below is my code. Any help is greatly appreciated.
library(shiny)
library(ROracle)
library(shinyjs)
library(shinyalert)
library(shinyWidgets)
ui <- fluidPage(
useShinyjs(),
useShinyalert(),
# Application title
titlePanel(fluidRow(
column(10, "RAINFALL AND ET DATA RETRIEVAL",align="center"),
column(2, offset = 0,img(height =90,width=250,src="logo.png",align="left"))
)),
# Sidebar with a slider input for number of bins
sidebarLayout(
sidebarPanel(width = 12,
helpText("Please enter IDs separated by commas. You can enter up to 25 IDs."),
textInput("PixelID", "Pixel ID(s)", value = ""),
helpText("OR"),
fileInput('datafile','Choose csv file to upload Pixel IDs.The csv file should have Pixel IDs in the first column WITHOUT ANY HEADER.',accept = c('csv','comma-separated-values','.csv')),
helpText("Please select a parameter you would like to retrieve."),
radioButtons("ParameterType", "Parameters",
choices = c("Rainfall Estimates","Evapotranspiration Estimates"),
selected = "None"),
dateInput("startdate","Data From", format = "yyyy-mm-dd",max = Sys.Date()),
dateInput("enddate","Data To", format = "yyyy-mm-dd",max = Sys.Date()),
br(), br(),
actionBttn("goButton","Go!",color = "default",style = "fill",size = "lg"),
br(),br(),
uiOutput("download"),
mainPanel(width=0)
)
)
server <- function(input, output, session) {
data<-eventReactive(input$goButton,{
if(is.null(input$PixelID) || input$PixelID == ""){
req(input$datafile)
infile<-input$datafile
PixelList<-read.table(infile$datapath, header = FALSE, sep = ",", stringsAsFactors = FALSE)
colnames(PixelList)<-"PixelNum"
PixelList_comma<-paste(PixelList$PixelNum, collapse = ",")} else{
if(input$PixelID != ""){
PixelList<-data.frame(strsplit(input$PixelID,","))
colnames(PixelList)<-"PixelNum"
PixelList_comma<-input$PixelID
}}
drv <- dbDriver("Oracle")
connection <- dbConnect(drv, username = "xxxx", password = "xxxxx", dbname = "xxxx")
if(input$ParameterType=="Rainfall Estimates"){
for(i in 1:nrow(PixelList)){
raindata<-dbGetQuery(connection, paste("select PIXEL, TO_CHAR(tsdatetime_dt, 'MM/DD/YYYY HH24:MI') as DATE_TIME, tsvalue_ms as RAINFALL from xxxx
where feature_id =",PixelList[i,1]," order by tsdatetime_dt", sep=""))
}
dbDisconnect(conn = connection)
}
return(raindata)
})
output$download <- renderUI({
downloadButton("downloadData", "Download")
})
output$downloadData <- downloadHandler(
filename = function() {
paste("testnexrad",".zip",sep = "")
},
content = function(file) {
for(i in 1:nrow(PixelList)){
#No idea what to do here
}
}
)
}
# Run the application
shinyApp(ui = ui, server = server)