javascript - 在 Shiny 的R中自动调整textAreaInput的大小

Question

我正在努力适应this SO answer关于如何通过javascript为shiny R自动调整文本区域输入的大小。理想情况下，我想避免使用shinyJS等帮助程序包。

首先，我尝试了一个纯 JavaScript 实现，其中我将 JavaScript 按原样加载到应用程序中(方法 1)。然后我尝试从 Shiny 的observeEvent中触发javascript函数(方法2)。

这两种方法都不起作用。看来我漏掉了一些东西。

方法 1:

library(shiny)

jsCode1 <- "
            var observe;
            if (window.attachEvent) {
            observe = function (element, event, handler) {
            element.attachEvent('on'+event, handler);
            };
            }
            else {
            observe = function (element, event, handler) {
            element.addEventListener(event, handler, false);
            };
            }
            function init () {
            var text = document.getElementById('text');
            function resize () {
            text.style.height = 'auto';
            text.style.height = text.scrollHeight+'px';
            }
            /* 0-timeout to get the already changed text */
            function delayedResize () {
            window.setTimeout(resize, 0);
            }
            observe(text, 'change',  resize);
            observe(text, 'cut',     delayedResize);
            observe(text, 'paste',   delayedResize);
            observe(text, 'drop',    delayedResize);
            observe(text, 'keydown', delayedResize);

            text.focus();
            text.select();
            resize();
            }

            init();
            "

shinyApp(ui = 

           fluidPage(

                        tags$script(jsCode1),

                        tags$head(

                          tags$style("
                                     textarea {
                                     border: 0 none white;
                                     overflow: hidden;
                                     padding: 0;
                                     outline: none;
                                     background-color: #D0D0D0;
                                     }
                                     "
                          )

                          ),

                               shiny::tagAppendAttributes(
                                 textAreaInput(inputId = "text",
                                               label = "Enter text here",
                                               placeholder = "insert your text here",
                                               width = "100%"),
                                 style = "width: 100%;")

                        ),

         server = function(input, output, session) {

         }
                      )

方法 2:

library(shiny)

jsCode2 <- "

            Shiny.addCustomMessageHandler('handler1', init);

            function init (el) {
            var text = document.getElementById(el);
            function resize () {
            text.style.height = 'auto';
            text.style.height = text.scrollHeight+'px';
            }
            /* 0-timeout to get the already changed text */
            function delayedResize () {
            window.setTimeout(resize, 0);
            }
            observe(text, 'change',  resize);
            observe(text, 'cut',     delayedResize);
            observe(text, 'paste',   delayedResize);
            observe(text, 'drop',    delayedResize);
            observe(text, 'keydown', delayedResize);

            text.focus();
            text.select();
            resize();
            }"

shinyApp(ui = 

           fluidPage(

                        tags$script(jsCode2),

                        tags$head(

                          tags$style("
                                     textarea {
                                     border: 0 none white;
                                     overflow: hidden;
                                     padding: 0;
                                     outline: none;
                                     background-color: #D0D0D0;
                                     }
                                     "
                          )

                          ),

                               shiny::tagAppendAttributes(
                                 textAreaInput(inputId = "text",
                                               label = "Enter text here",
                                               placeholder = "insert your text here",
                                               width = "100%"),
                                 style = "width: 100%;")

                        ),

         server = function(input, output, session) {

           observeEvent(input$text,{

             session$sendCustomMessage("handler1", message = "text")

           })

         }
                      )

Answer 1

可能是这样的情况:您尝试将调整大小事件附加到 textinput()，然后再将后者添加到 DOM。

我添加了一个事件监听器，它会等到 DOM 加载完毕后再附加调整大小事件。

document.addEventListener('DOMContentLoaded', function(event) {...})

shinyjs 会自动为您执行此操作。添加上面的事件监听器，就可以在不使用shinyjs的情况下使其工作。

Javascript代码:

jsCode <- "document.addEventListener('DOMContentLoaded', function(event) {
    var observe;
    if (window.attachEvent) {
      observe = function (element, event, handler) {
        element.attachEvent('on'+event, handler);
      };
    }
    else {
      observe = function (element, event, handler) {
        element.addEventListener(event, handler, false);
      };
    }
    function init () {
      var text = document.getElementById('text');
      function resize () {
        text.style.height = 'auto';
        text.style.height = text.scrollHeight+'px';
      }
      /* 0-timeout to get the already changed text */
        function delayedResize () {
          window.setTimeout(resize, 0);
        }
      observe(text, 'change',  resize);
      observe(text, 'cut',     delayedResize);
      observe(text, 'paste',   delayedResize);
      observe(text, 'drop',    delayedResize);
      observe(text, 'keydown', delayedResize);

      text.focus();
      text.select();
      resize();
    };init()
  })
"

应用程序:

library(shiny)

ui <- fluidPage(
  shiny::tags$script(jsCode),
  textAreaInput(inputId = "text", label = "a", value = "b")
)

server <- function(input, output, session) {
}

shinyApp(ui, server)