Integrate dropdown menus on app list elements

To integrate dropdown menus in a Phoenix Liveview app, you can use a combination of js, Hooks, CSS and your .leex and .ex code. You can expand on this concept to dynamically adjust your dropdown menu contents, and apply the dropdown in multiple places in your app.

.leex
Create adiv with one or more spans to define your dropdown menu. This example assumes you have multiple items to apply the menu to, you need to assign a unique value to the element, mapped against your app’s state. Apply as many span elements as you need for your menu options. Include a phx-hook reference if you want to listen for click and hover events to close the dropdown

You can customize your dropdown span rendering by examining socket.assigns values in the .leex file.

      <div class="element_container" id="element_container" phx-hook="DropdownContainer">
              <div class = "my_dropdown" phx-click="dropdown" onclick="dropdownOptions('<%= unique_element_id %>')">
                <div id="myDropDown<%= unique_element_id %>" class="dropdown-content">
                  <span phx-click="menu_option_1" phx-value-unique_element_id="<%= unique_element_id %>">Menu Option</span>
                </div>
              </div>
    </div>

Include a script element in your .leex to allow toggling of the dropdown menu on click events.

<script type="text/javascript">
        /* When the user clicks on the button, 
    toggle between hiding and showing the dropdown content */
      function dropdownOptions(player) {
        var b = "playerDropDown"
        var c = b.concat(player)
        document.getElementById(c).classList.toggle("show")
      }
</script>

CSS
Your CSS should include the following for dropdown rendering. The default behavior is display: none; until the show class is detected. The show class is added/removed/toggled by javascript in the .leex and .js files.

.chat_player_dropdown:hover, .chat_player_dropdown:focus {
  background-color: #ddd;
}

.my_dropdown {
  position: relative;
  font-weight: 100;
  font-size: 100%;
  color: #333333;
  cursor: pointer;
}

.dropdown-content {
  display: none;
  position: absolute;
  left: 24px;
  background-color: #f1f1f1;
  min-width: 55px;
  overflow: auto;
  box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
  padding-left: 10px;
  padding-right: 10px;
  padding-top: 5px;
  padding-bottom: 5px;
  z-index: 998;
}

.dropdown-content span {
  color: black;
  padding-left: 10px;
  padding-right: 10px;
  padding-top: 5px;
  padding-bottom: 5px;
  text-decoration: none;
  margin-top: 3px;
  line-height: 2.3;
}

.dropdown-content span:hover {
  background-color: #ddd;
}

.show {display: block;}

.js
You can add a Hook to allow the dropdown to disappear on click and hover events on nearby parts of the rendered DOM, to accommodate users that hover or click elsewhere after activating the dropdown

Hooks.DropdownContainer = {
	mounted() {

	    // Close the dropdown if the user clicks outside of it
	    window.onclick = function(event) {
		    if (!event.target.matches('.my_dropdown')) {
		      var dropdowns = document.getElementsByClassName('dropdown-content')
		      var i
		      for (i = 0; i < dropdowns.length; i++) {
		        var openDropdown = dropdowns[i]
		        if (openDropdown.classList.contains('show')) {
		          openDropdown.classList.remove('show')
		        }
		      }
		    }
	    }

		var item = document.getElementById("element_container");
	    item.addEventListener("mouseover", e => {
	       this.pushEvent("restore", {dropdown: "false"})
	    })

		var item = document.getElementById("other_element");
	    item.addEventListener("mouseover", e => {
	       this.pushEvent("restore", {dropdown: "false"})
	    })
	}
}

.ex
If you need to control how you render things while your dropdown is being displayed, you can track it by assigning a dropdown parameter in
socket.assigns, with a default value of “false”.

In some of your event handlers, you would assign dropdown to “false” as a means of allowing normal rendering to commence.

Add a handler as required to detect dropdown activation

  @impl true
  def handle_event("dropdown", _params, socket) do
    {:noreply, assign(socket, dropdown: "true")}
  end
2 Likes

Thank you so much for this detailed answer!! One question:could you clarify a little more on what you mean by assigning a unique value to the element, mapped against the app’s state ? I’m a little confused on what that would look like, and how I could assign a unique_element_id to each of the span options I need for the menu options.

You assign a unique_element_id to each element that you create with a for statement in your .leex file when you have a common element type, such as a list item. You would normally use a div to contain the unique identifier.

You can see this in action at https://shiptoaster.com, when you host a game, and click on a player or viewer in the left sidebar, where the list is a list of players/viewers, and each can have their own dropdown.

When you create your dropdown span elements in your .leex file, you can use your socket.assigns values to dynamically evaluate one or more of those values so that you can customize how your dropdown span elements are presented. As an example, if you mute a player, you can use that muted state to render a span’ that allows you to unmute that player.

1 Like