Polymer动画页面无法更改页面

Question

I can't change the page when i click the button in the logincard element. In the logincard element i have set the button's on-tap to {{onSignUp}}

What should i do? I get the error message: Uncaught TypeError: Cannot read property 'selected' of null

    <core-animated-pages id = "animatedPages" transitions="cross-fade" selected="{{moveCard}}" center >
        <section id="0">
            <div hero-id="hero" hero>
                <moha-logincard token="{{token}}" success="{{success}}" loginurl="{{loginurl}}" signup="{{signup}}" z="{{z}}" onLogin="{{close}}" onSignUp="{{goToSignUp}}">
                </moha-logincard>
            </div>
        </section>
        <section id="1">
            <div  hero-id="hero" hero>
                <moha-signupcard success="{{success}}" signupurl="{{signupurl}}" z="{{z}}" onSignUp="{{backToLogin}}"></moha-signupcard>
            </div></section>

    </core-animated-pages>
</template>

<script>
    Polymer('moha-login-page', {
        moveCard: "0",
        pages:document.querySelector('core-animated-pages'),
        signup: false,
        token: "",
        loginurl: "",
        signupurl: "",
        z: 2,
        close: function () {
            //dialógus becsukása ha van
        },
        goToSignUp: function () {
            // var pages = document.querySelector('core-animated-pages');
            //var pages = this.$.animatedPages;
            this.pages = document.querySelector('core-animated-pages');
           console.log(this.pages.selected);

            this.moveCard = "1";
            this.pages.selected = this.moveCard;
           console.log(this.pages.selected);

        },
        backToLogin: function () {
            this.moveCard = 0;
        }
    });
</script>

Answer 1

While I have no experience with core-animated-pages I highly doubt that

this.pages = document.querySelector('core-animated-pages');

will get you what you desire as the element may live in shadow DOM.

Try
this.pages = document.querySelectorAll('html /deep/ core-animated-pages');

and see if this solves your TypeError.