<block wx:if="{{item.blank}}"> <canvas id="canvas{{index}}" type="2d"> <cover-view class="canvas" mark:id="drawboard{{index}}" mark:cid="canvas{{index}}" style="width: 350rpx; height: 350rpx;" bindtouchstart="drawstart" bindtouchmove="drawing" bindtouchend="drawend" bindtouchcancel="drawend" binderror="drawend" bind:longpress="clearWord"/> </canvas> </block> let item = this.createSelectorQuery().select(`#canvas${this.blank_index[i]}`).fields({ node: true, size: true, rect: true }) console.log('错误发生前？',item) item.exec(res => { console.log(res, '？？？？？？') const { width, height, left, top } = res[0] const { dpr } = this.data this[`canvas${this.blank_index[i]}`] = res[0].node this[`drawboard${this.blank_index[i]}`] = this[`canvas${this.blank_index[i]}`].getContext('2d') this[`canvas${this.blank_index[i]}`].width = width * dpr this[`canvas${this.blank_index[i]}`].height = height * dpr this[`canvas${this.blank_index[i]}`].left = left this[`canvas${this.blank_index[i]}`].top = top this[`drawboard${this.blank_index[i]}`].scale(dpr, dpr) this[`drawboard${this.blank_index[i]}`].lineJoin = "round" this[`drawboard${this.blank_index[i]}`].lineCap = "round" this.clearDrawboard(this[`drawboard${this.blank_index[i]}`], this[`canvas${this.blank_index[i]}`]) })