组件中能使用getDrawableContext()吗？

子组件中能否使用getDrawableContext()方法？

<template>  
    <view>  
        <view ref="myyy"></view>  
    </view>  
</template>  
<script>  
    export default {  
        name: "s-goodsView",  
        props: {  
        },  
        data() {  
            return {  

            };  
        },  
        mounted() {  
            // setTimeout(() => {  
            //  this.drawHeader()  
            // }, 10000)  
            this.drawHeader()  
        },  
        methods: {  
            drawHeader() {  
                const refs = this.$refs['myyy'] as UniElement  
                let ctx = refs.getDrawableContext()  
                if (ctx == null) return  

            },  
        }  
    }  
</script>

执行这段报错，

16:03:19.135 ⁠‌error: java.lang.ClassCastException: io.dcloud.uts.UTSArray cannot be cast to io.dcloud.uniapp.runtime.UniElement‌  
16:03:19.135 at components/s-goodsView/s-goodsView.uvue:156:4  
16:03:19.135 154|    methods: {  
16:03:19.136 155|     drawHeader() {  
16:03:19.136 156|      const refs = this.$refs['myyy'] as UniElement  
16:03:19.136    |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  
16:03:19.136 157|      let ctx = refs.getDrawableContext()  
16:03:19.136 158|      if (ctx == null) {⁠

mounted中做延迟也不行