How Polymer Hero Transition works

Question

First off I'm having a tough time understanding the fundamentals of the hero-transition within Polymer. I am attempting to build a hero transition card like the one in the example provided by them, which can be found here. Below I've built the mini card and I'm just trying to understand the transition and how the larger card works with the smaller one.

My specific question is, how does the transition bind to each element? Do I need to complete the CSS for both before I can begin playing with the core-animated-pages? Does having an embedded template matter?

Any guidance would be extremely helpful.

<script src="../components/webcomponentsjs/webcomponents.js"></script>
<link rel="import" href="../components/core-animated-pages/core-animated-pages.html">
<link rel="import" href="../components/core-animated-pages/transitions/hero-transition.html">
<link rel="import" href="../components/paper-button/paper-button.html">
<link rel="import" href="../components/core-image/core-image.html">
<link rel="import" href="../components/paper-shadow/paper-shadow.html">
<polymer-element name="chip-card">
    <template>
        <style>
            #page2 {
                width: 100%;
                height: 100%;
            }
            #paper_shadow {
                position: relative;
                display: inline-block;
                font-family:'Roboto', sans-serif;
                font-size: 12px;
                color: white;
            }
            #chip_body {
                height: 400px;
                width: 300px;
                background-color: aqua;
                color: black;
            }
            #chip_top {
                background-color: deeppink;
                background-image: url();
                background-size: cover;
                background-position: center center;
                width: 100%;
                position: relative;
            }
            #chip_bottom {
                background-color: #fbfbfb;
                width: 100%;
                height: 20%;
                position: relative;
                font-size: 1.2em;
                word-wrap: break-word;
            }
            #text {
                padding-left: 5%;
                padding-right: 2.5%;
                overflow: hidden;
            }
            #coreImage {
                display: block;
            }
            #card_container {
                width: 70%;
                height: 600px;
                background-color: aqua;
                color: black;
            }
            #card_right {
                height: 100%;
                width: 30%;
            }
            #card_left {
                background-color: darkblue;
                height: 100%;
                width;
                70%;
            }
            #card_left_top {
                padding-right: 20px;
                padding-top: 20px;
                background-color: skyblue;
            }
            #circle {
                width: 30px;
                height: 30px;
                border-radius: 50%;
                background-color: red;
            }
            #header_text {
            }
            #card_content {
                width:100%;
                background-color: lightcoral;
            }
        </style>
        <core-animated-pages transitions="hero-transition" selected={{page}}>
            <section>
                <paper-shadow z="1" id='paper_shadow' on-mouseover="{{raise}}" on-mouseout="{{lower}}" animated=true; hero-p="" on-tap="{{transition}}">
                    <div id="chip_body" hero-id="chip_body" vertical layout center justified>
                        <div id="chip_top" flex>
                            <div id="coreImage">
                                <content select="#core-image"></content>
                            </div>
                        </div>
                        <div id="chip_bottom" vertical layout start-justified>
                            <div id='text'>
                                <content select="#chip_bottom"></content>
                            </div>
                        </div>
                    </div>
                </paper-shadow>
            </section>
            <section id="page2">
                <div id="card_container" hero-id="chip_body" on-tap="{{transition}}" hero=""></div>
            </section>
        </core-animated-pages>
    </template>
    <script>
        Polymer('chip-card', {
            page: 0,

            raise: function() {
                this.$.paper_shadow.setZ(2);
            },
            lower: function() {
                this.$.paper_shadow.setZ(1);
            },
            transition: function(e) {
                if (this.page === 0) {
                    this.$.paper_shadow = e.currentTarget;
                    this.page = 1;
                } else {
                    this.page = 0;
                }
            }

        });
    </script>
</polymer-element>

Answer 1

you are actually very close to a working transition with the code you have.

I've implemented a more complicated hero transition on my website and took some code from there to get yours to work.

    <core-animated-pages transitions="hero-transition" selected={{page}}>
        <section>
            <paper-shadow z="1" id='paper_shadow' on-mouseover="{{raise}}" on-mouseout="{{lower}}" hero-p on-tap="{{transition}}">
                <div id="chip_body" hero-id="chip_body" hero vertical layout center justified>
                    <div id="chip_top" flex>
                        <div id="coreImage">
                            <content select="#core-image"></content>
                        </div>
                    </div>
                    <div id="chip_bottom" vertical layout start-justified>
                        <div id='text'>
                            <content select="#chip_bottom"></content>
                        </div>
                    </div>
                </div>
            </paper-shadow>
        </section>
        <section id="page2">
            <div id="card_container" hero-id="chip_body" on-tap="{{transition}}" hero></div>
        </section>
    </core-animated-pages>

I've made but a few adjustments.

• First off, any hero parent element, with the hero-p attribute, should contain just that attribute. So no need for the quotation marks :)
  <paper-shadow hero-p .. >
• Every element that's part of the Hero transition, needs a hero attribute.
  Again, without the quotation marks. <div id="chip_body" .. hero .. >
• And the same thing goes for the element you're transitioning to.
  <div id="card_container" .. hero .. >

---

I've put a working version of your code on my website.
There's page containing the <chip-card> element and a second page containing the working template file.

Index page
Template file

Please note : I edited the reference to webcomponentsjs to conform with my folder structure.

Feel free to ask me if there's anything else!