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Animated Snackbar

Introduction

Snackbars provide brief feedback about an operation through a message at the bottom of the screen.

Setup

We use amp-bind to trigger the Snackbar...

<script async custom-element="amp-bind" src="https://cdn.ampproject.org/v0/amp-bind-0.1.js"></script>

... and amp-animation to show and hide the Snackbar.

<script async custom-element="amp-animation" src="https://cdn.ampproject.org/v0/amp-animation-0.1.js"></script>

The animation

We want to show a snackbar that disappears after a few seconds. This could be easily accomplished by adding a CSS class using amp-bind to show the snackbar and then using CSS animations to hide the snackbar after a few seconds. However, with this approach it's not possible to trigger the snackbar multiple times (the newly added CSS class won't dissappear).

We can solve this problem by using the amp-animation extension, which makes it possible to execute animations repeatedly. We define an animation that will slide-in the snackbar and then hide it after a few seconds using the offset attribute to time the different keyframes.

<amp-animation id="snackbarSlideIn"
  layout="nodisplay">
  <script type="application/json">
    [{
      "duration": "3s",
      "fill": "both",
      "easing": "ease-out",
      "iterations": "1",
      "selector": ".snackbar",
      "keyframes": [{
          "transform": "translateY(100%)"
        },
        {
          "transform": "translateY(0)",
          "offset": 0.1
        },
        {
          "transform": "translateY(0)",
          "offset": 0.9
        },

        {
          "transform": "translateY(100%)"
        }
      ]
    }]
  </script>
</amp-animation>

The snackbar

Our snackbar is a div containing the message. It's going to disappear after a few seconds so we don't provide any additional buttons to manually hide the snackbar. The text message is bound to an amp-state variable to make it's content configurable. This is not needed if the snackbar should always show the same message.

Hello World
<div class="snackbar"
  [text]="message">
  Hello World
</div>

The trigger

The snackbar animation is triggered via the restart action: on="tap:snackbarSlideIn.restart". We use the restart action to make it possible to override an already active animation. The input field simply updates the amp-state variable containing the snackbar's message.

<div class="trigger">
  <input on="input-debounced:AMP.setState({message: event.value})"
    value="Hello World">
  <button on="tap:snackbarSlideIn.restart">
    Show Snackbar
  </button>
</div>
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