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uniapp结合Canvas+renderjs根据经纬度绘制轨迹

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• 根据官方建议要想在 app-vue 流畅使用 Canvas 动画，需要使用 renderjs 技术，把操作canvas的js逻辑放到视图层运行，避免逻辑层和视图层频繁通信。
• 这里呢结合 renderjs 技术实现绘制轨迹图形。

你可能需要先了解renderjs如何数据通讯：renderjs 与 app-vue之间数据交互

html中使用canvas根据经纬度绘制轨迹

效果图

template

• coordsAll 监听数据变化，只要 coordsAll 数据改变，就是触发 initData 方法。

 <template><view class="map-track-wrap"><!-- xxx --><view class="track-list" :prop="coordsAll" :change:prop="canvas.initData"><!-- xxx --><view class="d-flex canvas-box"><canvas class="canvas" :class="`canvas${index}`"></canvas></view></view></view>
</template>

renderjs

<script module="canvas" lang="renderjs">export default {methods: {initData() {for (let i = 0; i < this.coordsAll.length; i++) {// 绘制图形this.draw(this.coordsAll[i], i);}},draw(locationList, idx) {let canvasHeight = 72,canvasWidth = 72,canvasEle = document.querySelectorAll(`.canvas${idx}>canvas`)[0],ctx = canvasEle.getContext('2d'),amuXArr = [],amuYArr = []for (let i = 0; i < locationList.length; i++) {amuXArr.push(locationList[i].lat);amuYArr.push(locationList[i].lng);}amuYArr = amuYArr.map((item) => {return item * -1;});let xMax = Math.max(...amuXArr);let xMin = Math.min(...amuXArr);let yMax = Math.max(...amuYArr);let yMin = Math.min(...amuYArr);let xScale = canvasWidth / (xMax - xMin);let yScale = canvasHeight / (yMax - yMin);let scale = xScale < yScale ? xScale : yScale;let xoffset = (canvasWidth - (xMax - xMin) * scale) / 2;let yoffset = (canvasHeight - (yMax - yMin) * scale) / 2;ctx.save(); // 保存状态ctx.translate(0, canvasHeight);ctx.rotate(-Math.PI / 2);ctx.beginPath();// 根据偏移量移动点位并画图ctx.moveTo((amuXArr[0] - xMin) * scale + xoffset,(yMax - amuYArr[0]) * scale + yoffset);for (let i = 1; i < amuXArr.length; i++) {ctx.lineTo((amuXArr[i] - xMin) * scale + xoffset,(yMax - amuYArr[i]) * scale + yoffset);}ctx.strokeStyle = '#1FE298';ctx.stroke();ctx.restore(); // 恢复状态}}}
</script>

js

• renderjs中不支持uni.request，所以请求后台获取数据操作在script中进行，然后监听参数变化，将参数传递过来进行渲染。

searchList() {      	// 处理数据let list = this.dataList;if (list.length > 0) {for(let i = 0; i < list.length; i++) {let tmpLocation = list[i].locations;// 页面监听 coordsAll，把数据传递renderjs，会触发 initData 方法this.coordsAll.push(JSON.parse(tmpLocation));}}
}

数据结构

• 测试数据，具体根据个人所需处理数据

[{locations: [{"lng": 113.980502,"lat": 22.54161},{"lng": 113.972839,"lat": 22.533976},{"lng": 113.98925,"lat": 22.524669},{"lng": 113.990034,"lat": 22.537097},{"lng": 114.00916,"lat": 22.534477}]},{locations: [{"lng": 113.924271,"lat": 22.537654},{"lng": 113.9367,"lat": 22.532806},{"lng": 113.928494,"lat": 22.518594},{"lng": 113.942673,"lat": 22.524502},{"lng": 113.944302,"lat": 22.538601}]},{locations: [{"lng": 113.98049,"lat": 22.54301},{"lng": 114.06374,"lat": 22.51134},{"lng": 114.06259,"lat": 22.50951},{"lng": 114.06178,"lat": 22.51031},{"lng": 113.96047,"lat": 22.54611}]}
]