設 Shiny UI

以 bslib 題、現代布局原、自定 CSS 設響、可訪 Shiny 介。

用

• 從始建新 Shiny UI
• 舊 app 由 fluidPage 現代化至 bslib
• 施品題（色、字）於 Shiny
• 使 Shiny 於諸屏響
• 改 Shiny 可訪

入

• 必：app 用與目眾
• 必：布類（sidebar、navbar、fillable、dashboard）
• 可：品色與字
• 可：用自定 CSS/SCSS（默：僅 bslib）
• 可：可訪求（WCAG 級）

行

一：擇頁布

bslib 供諸頁構：

# Sidebar layout — most common for data apps
ui <- page_sidebar(
  title = "My App",
  sidebar = sidebar("Controls here"),
  "Main content here"
)

# Navbar layout — for multi-page apps
ui <- page_navbar(
  title = "My App",
  nav_panel("Tab 1", "Content 1"),
  nav_panel("Tab 2", "Content 2"),
  nav_spacer(),
  nav_item(actionButton("help", "Help"))
)

# Fillable layout — content fills available space
ui <- page_fillable(
  card(
    full_screen = TRUE,
    plotOutput("plot")
  )
)

# Dashboard layout — grid of value boxes and cards
ui <- page_sidebar(
  title = "Dashboard",
  sidebar = sidebar(open = "closed", "Filters"),
  layout_columns(
    fill = FALSE,
    value_box("Revenue", "$1.2M", theme = "primary"),
    value_box("Users", "4,521", theme = "success"),
    value_box("Uptime", "99.9%", theme = "info")
  ),
  layout_columns(
    card(plotOutput("chart1")),
    card(plotOutput("chart2"))
  )
)

得：布符 app 之導航與內容需。

敗：布不適→查用 page_sidebar() / page_navbar()（bslib），非 fluidPage() / navbarPage()（base shiny）。bslib 默認更佳且支題。

二：配 bslib 題

my_theme <- bslib::bs_theme(
  version = 5,                      # Bootstrap 5
  bootswatch = "flatly",            # Optional preset theme
  bg = "#ffffff",                   # Background color
  fg = "#2c3e50",                   # Foreground (text) color
  primary = "#2c3e50",              # Primary brand color
  secondary = "#95a5a6",            # Secondary color
  success = "#18bc9c",
  info = "#3498db",
  warning = "#f39c12",
  danger = "#e74c3c",
  base_font = bslib::font_google("Source Sans Pro"),
  heading_font = bslib::font_google("Source Sans Pro", wght = 600),
  code_font = bslib::font_google("Fira Code"),
  "navbar-bg" = "#2c3e50"
)

ui <- page_sidebar(
  theme = my_theme,
  title = "Themed App",
  # ...
)

開發時用互動題編：

bslib::bs_theme_preview(my_theme)

得：app 以一致品色、字、Bootstrap 5 組件現。

敗：字不載→查網（Google Fonts 需之）或換系字：font_collection("system-ui", "-apple-system", "Segoe UI")。題變量不施→查 theme 傳至頁函。

三：以卡與列建布

ui <- page_sidebar(
  theme = my_theme,
  title = "Analysis Dashboard",
  sidebar = sidebar(
    width = 300,
    title = "Filters",
    selectInput("dataset", "Dataset", choices = c("iris", "mtcars")),
    sliderInput("sample", "Sample %", 10, 100, 100, step = 10),
    hr(),
    actionButton("refresh", "Refresh", class = "btn-primary w-100")
  ),

  # KPI row — non-filling
  layout_columns(
    fill = FALSE,
    col_widths = c(4, 4, 4),
    value_box(
      title = "Observations",
      value = textOutput("n_obs"),
      showcase = bsicons::bs_icon("table"),
      theme = "primary"
    ),
    value_box(
      title = "Variables",
      value = textOutput("n_vars"),
      showcase = bsicons::bs_icon("columns-gap"),
      theme = "info"
    ),
    value_box(
      title = "Missing",
      value = textOutput("n_missing"),
      showcase = bsicons::bs_icon("exclamation-triangle"),
      theme = "warning"
    )
  ),

  # Main content row
  layout_columns(
    col_widths = c(8, 4),
    card(
      card_header("Distribution"),
      full_screen = TRUE,
      plotOutput("main_plot")
    ),
    card(
      card_header("Summary"),
      tableOutput("summary_table")
    )
  )
)

諸布原：

• layout_columns() — 響格，含 col_widths
• card() — 內容器，可選頭／尾
• value_box() — KPI 顯，含徽與題
• layout_sidebar() — 卡內嵌 sidebar
• navset_card_tab() — 有頁標之卡

得：響格布應屏尺。

敗：寬屏列意外堆→查 col_widths 和為 12（Bootstrap 格）。卡重疊→非填列宜 fill = FALSE。

四：添動 UI 素

server <- function(input, output, session) {
  output$dynamic_filters <- renderUI({
    data <- current_data()
    tagList(
      selectInput("col", "Column", choices = names(data)),
      if (is.numeric(data[[input$col]])) {
        sliderInput("range", "Range",
          min = min(data[[input$col]], na.rm = TRUE),
          max = max(data[[input$col]], na.rm = TRUE),
          value = range(data[[input$col]], na.rm = TRUE)
        )
      } else {
        selectInput("values", "Values",
          choices = unique(data[[input$col]]),
          multiple = TRUE
        )
      }
    )
  })

  # Conditional panels (no server round-trip)
  # In UI:
  # conditionalPanel(
  #   condition = "input.show_advanced == true",
  #   numericInput("alpha", "Alpha", 0.05)
  # )
}

得：UI 素依使擇及數動更。

敗：動 UI 閃→用 conditionalPanel()（CSS 基）代 renderUI()。動入於再渲失值→加 session$sendInputMessage() 復態。

五：添自定 CSS/SCSS（可選）

求 bslib 題變量外之樣：

# Inline CSS
ui <- page_sidebar(
  theme = my_theme,
  tags$head(tags$style(HTML("
    .sidebar { border-right: 2px solid var(--bs-primary); }
    .card-header { font-weight: 600; }
    .value-box .value { font-size: 2.5rem; }
  "))),
  # ...
)

# External CSS file (place in www/ directory)
ui <- page_sidebar(
  theme = my_theme,
  tags$head(tags$link(rel = "stylesheet", href = "custom.css")),
  # ...
)

SCSS 與 bslib 整合：

my_theme <- bslib::bs_theme(version = 5) |>
  bslib::bs_add_rules(sass::sass_file("www/custom.scss"))

得：自定樣施而不破 bslib 題。

敗：自定 CSS 與 bslib 衝→用 Bootstrap CSS 變量（var(--bs-primary)）代硬編色→題變則自定樣傳播。

六：保可訪

# Add ARIA labels to inputs
selectInput("category", "Category",
  choices = c("A", "B", "C")
) |> tagAppendAttributes(`aria-describedby` = "category-help")

# Add alt text to plots
output$plot <- renderPlot({
  plot(data(), main = "Distribution of Values")
}, alt = "Histogram showing the distribution of selected values")

# Ensure sufficient color contrast in theme
my_theme <- bslib::bs_theme(
  version = 5,
  bg = "#ffffff",      # White background
  fg = "#212529"       # Dark text — 15.4:1 contrast ratio
)

# Use semantic HTML
tags$main(
  role = "main",
  tags$h1("Dashboard"),
  tags$section(
    `aria-label` = "Key Performance Indicators",
    layout_columns(
      # value boxes...
    )
  )
)

得：app 符 WCAG 2.1 AA 之色對、鍵導、屏讀相容。

敗：用瀏覽器開發工具 Lighthouse 可訪審試。以 WebAIM 對比查色對。保諸互動素可鍵焦。

驗

• 頁布於桌與手寬皆正渲
• bslib 題一致施於諸組件
• value box 以正題及徽顯
• 卡於響格正縮
• 自定 CSS 用 Bootstrap 變量，非硬編
• 諸圖有 alt 文為屏讀
• 色對符 WCAG AA（文 4.5:1）
• 互動素可鍵訪

忌

• 混新舊 Shiny UI：勿混 fluidPage() 與 bslib 組件→專用 page_sidebar()、page_navbar()、或 page_fillable()
• CSS 硬編色：用 var(--bs-primary) 代 #2c3e50→硬編色題變則破
• 非填列忘 fill = FALSE：value box 列與摘列常不宜伸→設 fill = FALSE
• 離網境之 Google Fonts：部至隔網→用系字或自寓字檔代 font_google()
• 略手機：以瀏覽器響模試。layout_columns 窄屏自動堆，自定 CSS 則或否

參

• scaffold-shiny-app
• build-shiny-module
• optimize-shiny-performance
• review-web-design
• review-ux-ui