对话框不会显示在vuetify 3中

<template>
  <div>
    <v-btn @click="showDialog = true">打开对话框</v-btn>
    <v-dialog v-model="showDialog">
      <v-card>
        <v-card-title>对话框标题</v-card-title>
        <v-card-text>
          对话框内容
        </v-card-text>
        <v-card-actions>
          <v-btn @click="showDialog = false">关闭对话框</v-btn>
        </v-card-actions>
      </v-card>
    </v-dialog>
  </div>
</template>

<script>
export default {
  data() {
    return {
      showDialog: false
    };
  }
};
</script>