library(shiny)
library(shinyBS)

app = shinyApp(
  ui =
    fluidPage(
      sidebarLayout(
        sidebarPanel(
          HTML("This button will open and close Panel 1 without using any R code."),
          actionButton(
            inputId="p1Button",
            "Push Me!",
            class="btn btn-primary",
            type="button",
            "data-toggle"="collapse",
            "data-target"="#panel-1",
            "aria-expanded"="false",
            "aria-controls"="collapseExample"
          ),
          selectInput(
            "styleSelect",
            "Select style for Panel 1",
            c("default", "primary", "danger", "warning", "info", "success"))
        ),
        mainPanel(
          bsCollapse(
            id = "collapseExample",
            open = "Panel 2",
            bsCollapsePanel(
              id="panel-1",
              title="Panel 1",
              "This is a panel with just text ",
              "and has the default style. You can change the style in ",
              "the sidebar.",
              style = "info"),
            bsCollapsePanel(
              id="panel-2",
              title="Panel 2",
              "This panel has a generic plot. ",
              "and a 'success' style.",
              plotOutput("genericPlot"),
              style = "success")
          )
        )
      )
    ),
  server =
    function(input, output, session) {
      output$genericPlot <- renderPlot(plot(rnorm(100)))
      observeEvent(input$styleSelect, ({
        updateCollapse(session, "collapseExample", style = list("Panel 1" = input$styleSelect))
      }))
    }
)