StopApp | stop apps when you do not need to use | Android library

I use shiny modules to update a large number of value boxes. The annoying part is the value boxes donot seem to scale above 10 or 20 as their updating is causing annoying flickers. Even those boxes whose values are not changing on the next invalidation, flicker. Ideally if the value is not changing the box should not refresh.

A representative shiny app using shiny modules is presented to replicate the problem. When the value of N is 4 or 5 the number of boxes are small and the updates happen instantaneously. As you increase N to 10 it gets noticeable and at N = 20 the flicker is unbearable.

How can I update the interface while processing data?

Here is the full story:

I am running a shiny app in a docker container. Before starting the app, I need to download a substantial amount of data (which takes some time). During that time it is not possible to connect to the shiny web server – since it has not started yet. However, I would like to make a simple page "Please wait, downloading data (XX%)" or something to that effect, and once the data is loaded, stop the app and run another one.

Below is a bit of code that kind of works. That is, the app runs, executes the "processing block" and when "data loading" is finished, stopApp is called and the results are returned. However, output is not being rendered until all the "work" has been done.

The following Shiny app has 3 buttons (blue when inactive). When a button is clicked (active) it should turn red until another button is clicked. If the user clicks elsewhere in the app (e.g. background, or any other widget than the buttons), the clicked button should stay red.

I need to call a function in my shiny app that pastes together the code that is to be executed.

(Why? I have many conditional inputs which are dynamically called upon to be worked with. Because of that the conditional inputs differ with the category selected in radiobuttons by the user.)

However, my app throws an error of "object 'input' not found".

Thus: How can my function access all the input$... variables?

MWE:

I am creating a custom RStudio Project Template as detailed here.

I have everything working to create a new project, and I also have the Shiny app working by itself.

However, I would now like to synchronously run the app in what amounts to my hello_world() function in the above webpage.

I can write wrapper functions around my Shiny app that work as desired outside of the context of making a new project from a template via the RStudio menus, but in the context of creating a new project, it is as if the line to run the app is not present as no app appears, and there are no messages, warnings, or errors issued.

I do have a bit of code executed within session$onSessionEnded() (such as a DBI::dbDisconnect()) of a Shiny app and I wonder the best practice to trigger it directly from the R code (for instance when a condition is not met, you close the app but also want to trigger this bit of code).

stop() will stop the R code (but not the app itself letting a "ghost" app) whereas stopApp() will close the app without triggering the session$onSessionEnded()

Should I for instance create a function that I should call before stopApp()ing or is there a way to tell to the application to trigger the session$onSessionEnded()? Like a session$endSession()?

I created a simple survey form in R Shiny (see code underneath). Now I would like to add some functionality that requires input on all questions on a specific page, before the 'Next' button works. So, if you press 'next' on the first page, but have not answered the first three questions, an alert/error message must appear. The same goes for the second, third, fourth page etc. This example has a few questions, but my final questionnaire would have around 15-20 questions.

It would be great if someone could help me out!

I'm continuing to try and understand the basics of shiny. I am now trying to take a user input via a text box (input$answer), have a conditional test based on that input (input$answer == "xyz"), and generate outputs based on this condition (if { } else { }).

I think I got much of the basics down. I can get a user input, I have turned this into a reactive value so I can generate a query in an if-statement without getting an error. And I can use that user input to generate an output after the answer is submitted.

There are two problems though:

1. The query (isolate(input$answer) == "Hello") is never TRUE since the value of isolare(input$answer) always remains the value it is first assigned. In the current case that is "Enter text..." but the behavior doesn't change if I leave this blank (it just assumes "" as the value). If I change the statement to if (isolate(input$answer) == "Enter text...") the evaluation will always be TRUE. Why does this value not change even though in the subsequent paste0("Your answer of ",input$answer, " is incorrect!") }) the value is updated correctly?
2. Is there a way to prevent the correct/incorrect evaluation at the startup of the server and only have it kick it when the submit button has been hit for the first time?

I'm trying to find my way around building some basic shiny tools to display some of the data I'm generating and analysis. Part of the intended workflow is to use one app for the user to select the data that should be displayed and then call a second module that would be specific for the dataset selected. I'm playing around with a toy-example to figure out how to collect inputs and then start a new module based on that info.

I got everything about the data input working, but I am not able to figure out how to pass information from the shinyApp(ui = ui_parameter_selection, server = server_parameter_selection) call on to the main code. Specifically, I would like to retrieve the last values for input$number, input$range[[1]], and input$range[[2]] once the shinyApp is closed and continue working with them.