Saving dotchart with shiny - r

Question

Do you see any mistake here?
the ggsave works, but png(file=file) part not - it saves empty white image.
output$savePlotAmount <- downloadHandler(
filename = "amount.png",
content = function(file) {
if(input$plotType == "dot"){
png(file = file)
plotAmount()
dev.off()
}else{
ggsave(plotAmount(), filename = file)
}
})
I spent "hours" on trying to repair it but I don't know what's going on. Sorry that the example is not reproductible, but it is to hard to reproduct all app.
EDIT:
What is plotAmount():
plotAmount <- reactive({
if(input$plotType == "violin") {
plotAmount <- ggplot(values$x, aes_string(x = input$groupedBy, y = input$yVariableContinous)) +
geom_violin() +
ggtitle(paste0(input$yVariableContinous, " grouped by ", input$groupedBy)) +
scale_y_continuous(limits = c(0, quantile(values$x[,input$yVariableContinous] , 0.95, na.rm = T)))
}
if(input$plotType == "boxplot") {
plotAmount <- ggplot(values$x, aes_string(x = input$groupedBy, y = input$yVariableContinous)) +
geom_boxplot(outlier.shape = NA) +
ggtitle(paste0(input$yVariableContinous, " grouped by ", input$groupedBy)) +
scale_y_continuous(limits = c(0, quantile(values$x[,input$yVariableContinous] , 0.95, na.rm = T)))
}
if(input$plotType == "dot") {
var <- ifelse(input$groupedBy == 1, input$xVariable, input$groupedBy)
agregat <- aggregate(x = values$x[,input$yVariableContinous], by = list(g = values$x[,var], xx = values$x[,input$xVariable]), FUN = input$valueAs)
dotchart(agregat$x, labels = agregat$xx,
groups = as.factor(agregat$g),
color = brewer.pal(9,"Set1")[as.numeric(as.factor(agregat$g))],
xlab = "salary",
cex = .75,
main = paste0(input$yVariableContinous, " for ", input$xVariable,
"\ngrouped by ", input$groupedBy),
xlim = c(min(values$x[,input$yVariableContinous], na.rm = T), quantile(values$x[,input$yVariableContinous] , 0.95, na.rm = T)),
pch = 16
)
}

Answer 1

ggplot2 plots need to be print()'d to render.