The problem of appear in vue

< div id= "app" >

    <transition
        appear
        enter-active-class="animated swing"    
        leave-active-class="animated shake"
        appear-class="animated swing"
        appear-to-class="animated shake"
        appear-active-class="animated shake"
    >
        <div v-if="show">hello world</div>
    </transition>
    <button @click="handleClick"></button>
</div>

the code written in this way (prerequisite: animate.css is referenced as a library), why does the transition effect of the dom node in the initial rendering not take effect?

Apr.17,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b3ef63-4f0bc.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3ef63-4f0bc.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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