R Shiny key input binding

Question

In a Shiny application, is it possible to have a binding that listens to what key a user presses down?

I\'m not too familiar with JavaScript, but I\'m looking for s

Answer 1

If you want this to work for multiple presses, you can create an additional press counter that updates on a key press, bind that value to a different variable, and watch the counter rather than the key code. Here's some example UI code:

  tags$script('
    pressedKeyCount = 0;
    $(document).on("keydown", function (e) {
       Shiny.onInputChange("pressedKey", pressedKeyCount++);
       Shiny.onInputChange("pressedKeyId", e.which);
    });'
  )

And associated server code:

  observeEvent(input$pressedKey, {
    if(input$pressedKeyId >= 49 && input$pressedKeyId <= 57){ # numbers
      values$numClick <- (input$pressedKeyId - 48);
      flipNumber();
    }
    if(input$pressedKeyId >= 37 && input$pressedKeyId <= 40){ # arrow keys
      arrowCode <- input$pressedKeyId - 37;
      xInc <- ((arrowCode+1) %% 2) * (arrowCode - 1);
      yInc <- ((arrowCode) %% 2) * (arrowCode - 2) * -1;
      if(!any(values$click == c(-1,-1))){
        values$click <- (((values$click - 1) + c(xInc, yInc) + 9) %% 9) + 1;
      }
    }
  });