Shiny Customized Widgets

Zhengjia Wang

1. Styled Action Button

The default shiny actionButton cannot fully use Bootstrap theme or the full features defined by HTML. For example, the button class is always btn btn-default and we can’t disable/enable the button in an easy way.

actionButtonStyled solves these two problems:

The usage is listed as follows:

# UI function
actionButtonStyled(inputId, label, icon = NULL, width = NULL, 
                   btn_type = "button", type = "primary", class = "", ...)

# Update function
updateActionButtonStyled(session, inputId, label = NULL, icon = NULL,
                         type = NULL, disabled = NULL, ...)



2. Compound Inputs (grouped Inputs)

compoundInput2 provides group inputs where each group contains multiple shiny inputs. For examples

  'compound', 'Group Label', label_color = 1:10,
  components = div(
    textInput('txt', 'Text'),
    selectInput('sel', 'Select', choices = 1:10, multiple = TRUE),
    sliderInput('sli', 'Slider', max=1, min=0, val=0.5)
  ), max_ncomp = 10, min_ncomp = 0, initial_ncomp = 1

will create a list of input groups with minimum of 0 but maximum of 10. User can control the size of groups by pressing + and - buttons. The value input$components looks like this:

#> [[1]]
#> [[1]]$txt
#> [1] ""
#> [[1]]$sel
#> [1] "1" "3" 
#> [[1]]$sli
#> [1] 0.5
#> [[2]]

I found this input extremely useful in clinic trial when the experiment condition is grouped and developers don’t know ahead the number of condition groups.

The further details can be found with demo('example-compountInput2', package='dipsaus'). The source file can be found using system.file('demo/example-compountInput2.R', package='dipsaus').

3. Synchronize Multiple Inputs

sync_shiny_inputs provides a way to update among multiple inputs with no dead-locks. For example, input A (textInput) shares the same information as input B (sliderInput). Updating A would trigger B to update. What if you want A to be updated when B is changed? The following code might cause recursive updates:

# Bad example
observeEvent(input$A, {
  updateSliderInput(session, 'B', value = input$A)
observeEvent(input$B, {
  updateTextInput(session, 'A', value = input$B)

In this case, you can use sync_shiny_inputs:

sync_shiny_inputs(input, session, inputIds = c('A', 'B'), uniform = list(
  function(b){ b }
), updates = list(
  function(a){updateTextInput(session, 'A', value = a)},
  function(b){updateSliderInput(session, 'B', value = b)}

inputIds refers to the input ID to be synchronized. When one or more of the inputs are changed, the value will be passed to the corresponding uniform functions and stored, then updates will notify each inputs to update the UI values. The input of updates is the stored value.

For example, if input A is changed from "0" to "1", then the first function of uniform is triggered, function(a){as.numeric(a)} will be evaluated with a="1". The result, which is numeric 1 will be stored. Next, each functions in updates will be called, with 1 (stored in the previous step) as input, results in changing the slider input B to 1. This whole process will not trigger A to re-update.