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A Calculation in process busy indicator for shiny application is useful especially for the application that take long time to calculate result. I used to developed an application do model fitting which need more than 10 seconds! Users may lose their patience if the application doesn’t response after several seconds! < !-- more --> One solution is add a process bar, take a look of the threads in Shiny Google Group and Stackoverflow. The shortcoming of a process bar is you need to give the arguments min and max values, which for a lot of application is not available. Here I share a simple method add a busy indictor when calculation is undergoing.
Take a look of the html source of a Shiny application which need some time to calculate result, we can find the <html> tag has a class named “shiny-busy” when the calculation is under going and disappear when calculation is finish. So, the simple idea comes out: write JavaScript code to monitor the class of <html>, if the class equal to “shiny-busy”, then show a busy indictor (gif picture), otherwise hide the indictor!
Create a busy indictor div in “ui.R”:
ruby
div(class = "busy",
p("Calculation in progress.."),
img(src="ajaxloaderq.gif")
)
Include the JavaScript in head:
ruby
tagList(
tags$head(
tags$link(rel="stylesheet", type="text/css",href="style.css"),
tags$script(type="text/javascript", src = "busy.js")
)
)
Here is the souce code for “busy.js”:
ruby
setInterval(function(){
if ($('html').attr('class')=='shiny-busy') {
$('div.busy').show()
} else {
$('div.busy').hide()
}
},100)
We can also use “style.css” to makeup busy indictor’s appearance:
ruby
div.busy {
position:absolute;
top: 40%;
left: 50%;
margin-top: -100px;
margin-left: -50px;
display:none;
background: rgba(230, 230, 230, .8);
text-align: center;
padding-top: 20px;
padding-left: 30px;
padding-bottom: 40px;
padding-right: 30px;
border-radius: 5px;
}
Here is the source code and demo.
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