openlayers 绘图功能，编辑多边形，select，snap组件的使用（六）

本篇介绍一下vue3-openlayers的select，snap的使用

1 需求

点击开始绘制按钮开始绘制多边形，可以连续绘制多个多边形
点击撤销上步按钮，撤销上一步绘制点
绘制多个多边形（或编辑多边形时），鼠标靠近之前的已绘制完的多边形顶点时，自动吸附
点击结束绘制按钮，绘制完成，点击高亮选中多边形，开启编辑模式，显示顶点（调节点）进行编辑

2 分析

主要是vue3-openlayers 中 draw，select，snap，modify 功能的使用

3 实现

3.1 简单实现

<template><ol-map:loadTilesWhileAnimating="true":loadTilesWhileInteracting="true"style="width: 100%; height: 100%"ref="mapRef"><ol-viewref="view":center="center":rotation="rotation":zoom="zoom":projection="projection"/><ol-vector-layer><ol-source-vector :projection="projection" :wrapX="false"><ol-interaction-drawref="drawRef":type="'Polygon'":source="source"@drawend="drawend"@drawstart="drawstart"><ol-style :overrideStyleFunction="handleStyleFunction"> </ol-style></ol-interaction-draw><ol-interaction-modifyref="modifyRef"v-if="modifyFlag":features="selectedFeatures":pixelTolerance="10":insertVertexCondition="handleInsertVertexCondition"@modifyend="handleModifyEnd"><ol-style :overrideStyleFunction="handleModifyStyleFunction"> </ol-style></ol-interaction-modify><ol-interaction-snap :edge="false" /></ol-source-vector><ol-style :overrideStyleFunction="styleFunction"> </ol-style></ol-vector-layer><ol-interaction-select ref="selectRef"  :features="selectedFeatures" @select="handleSelect" :condition="selectCondition"><ol-style :overrideStyleFunction="selectStyleFunc"> </ol-style></ol-interaction-select></ol-map><div class="toolbar"><el-button type="primary" @click="handleClick">{{ drawFlag ? '结束' : '开始' }}绘制</el-button><el-button type="warning" :disabled="!drawFlag" @click="handleCancelClick">撤销上步</el-button></div>
</template><script setup lang="ts">
import { Collection } from 'ol';
import { FeatureLike } from 'ol/Feature';
import { LineString, Point } from 'ol/geom';
import { DrawEvent } from 'ol/interaction/Draw';
import { Circle, Fill, Stroke, Style } from 'ol/style';
const center = ref([121, 31]);
const projection = ref('EPSG:4326');
const zoom = ref(5);
const rotation = ref(0);
const features = ref(new Collection()); //保存绘制的features
const selectedFeatures = ref(new Collection()); //保存绘制的features
const source = ref([]);
const mapRef = ref();
const drawRef = ref();
const selectRef = ref();
const modifyRef = ref();
const drawFlag = ref(false);
const modifyFlag = ref(true);
const selectConditions = inject('ol-selectconditions');const selectCondition = selectConditions.click;onMounted(() => {drawRef.value.draw.setActive(false);modifyRef.value.modify.setActive(false);
});const drawstart = (event: Event) => {console.log(event);
};const drawend = (event: DrawEvent) => {console.log(event.feature.getGeometry());
};const handleClick = () => {drawFlag.value = !drawFlag.value;drawRef.value.draw.setActive(drawFlag.value);// modifyFlag.value=!drawFlag.value;modifyRef.value.modify.setActive(!drawFlag.value);selectRef.value.select.setActive(!drawFlag.value);selectRef.value.select.getFeatures().clear();
};
const handleCancelClick = () => {drawRef.value.draw.removeLastPoint();
};const handleSelect = e => {modifyRef.value.modify.setActive(false);// modifyFlag.value=false;if (!e.selected.length) {selectedFeatures.value.clear();selectRef.value.select.getFeatures().clear();} else {nextTick(()=>{// modifyFlag.value=true;modifyRef.value?.modify.setActive(true);selectedFeatures.value=e.target.getFeatures();})}
};const handleStyleFunction = (feature: FeatureLike, currentStyle: Style) => {const geometry = feature.getGeometry();const coord = geometry.getCoordinates();const type = geometry.getType();const styles: Array<Style> = [];if (type === 'LineString') {for (let i = 0; i < coord.length - 1; i++) {styles.push(new Style({geometry: new LineString([coord[i], coord[i + 1]]),stroke: new Stroke({color: 'orange',lineDash: coord.length > 2 && i < coord.length - 2 ? [] : [10],width: 2})}));}}return styles;
};const handleInsertVertexCondition = e => {return false;
};const handleModifyStyleFunction = (feature: FeatureLike, currentStyle: Style) => {const coord = feature.getGeometry().getCoordinates();const layer = mapRef.value.map.getLayers().item(0);const features = layer.getSource().getFeatures();const coords = features.map(feature => feature.getGeometry().getCoordinates()).flat(2);let style = undefined;// 只有鼠标在顶点时才能触发编辑功能if (coords.find(c => c.toString() === coord.toString())) {style = new Style({geometry: new Point(coord),image: new Circle({radius: 6,fill: new Fill({color: '#ffff'}),stroke: new Stroke({color: 'red',width: 2})})});}return style;
};const handleModifyEnd = e => {features.value.push(e.feature); //这里可以把编辑后的feature添加到layer绑定的features中console.log('modifyend', e.features);
};const styleFunction = (feature: FeatureLike, currentStyle: Style) => {const styles = [];styles.push(new Style({fill: new Fill({color: [128, 128, 255, 0.5]}),stroke: new Stroke({color: 'blue',width: 2})}));return styles;
};const selectStyleFunc = feature => {const styles = [];const coord = feature.getGeometry().getCoordinates().flat(1);for (let i = 0; i < coord.length - 1; i++) {styles.push(new Style({geometry: new Point(coord[i]),image: new Circle({radius: 4,fill: new Fill({color: '#ffff'}),stroke: new Stroke({color: 'orange',width: 2})})}));}styles.push(new Style({stroke: new Stroke({color: 'orange',width: 2}),fill: new Fill({color: '#ffff'})}));return styles;
};
</script>
<style scoped lang="scss">
.toolbar {position: absolute;top: 20px;left: 100px;
}
</style>

存在问题（vue3-openlayers官网modify示例也存在这两个个问题）：

当绘制多个多边形时，只要一个多边形被编辑过，当编辑其他多边形时，尽管高亮选中的是当前多边形，但是之前编辑过的多边形也可以被编辑
当两个多边形顶点重叠时，无法再分开，会导致同时编辑两个多边形

分析：
modify组件没有仅仅使用当前选中的多边形，而是把select过的都进入编辑状态（其实原生写法也有这个问题，试着把modify传入的features参数绑定值从select.value.getFeatures()改为一个ref(new Collection()),在select组件的select事件中把选中的feature压入这个ref,既可以复现上面两个问题）

解决：
modify添加v-if,强制重新渲染（会导致snap不会吸附，个人觉得可以接受）

3.2 重新实现

<template><ol-map:loadTilesWhileAnimating="true":loadTilesWhileInteracting="true"style="width: 100%; height: 100%"ref="mapRef"><ol-viewref="view":center="center":rotation="rotation":zoom="zoom":projection="projection"/><ol-vector-layer><ol-source-vector :projection="projection" :wrapX="false"><ol-interaction-drawref="drawRef":type="'Polygon'":source="source"@drawend="drawend"@drawstart="drawstart"><ol-style :overrideStyleFunction="handleStyleFunction"> </ol-style></ol-interaction-draw><ol-interaction-modifyref="modifyRef"v-if="modifyFlag":features="selectedFeatures":pixelTolerance="10":insertVertexCondition="handleInsertVertexCondition"@modifyend="handleModifyEnd"><ol-style :overrideStyleFunction="handleModifyStyleFunction"> </ol-style></ol-interaction-modify><ol-interaction-snap :edge="false" /></ol-source-vector><ol-style :overrideStyleFunction="styleFunction"> </ol-style></ol-vector-layer><ol-interaction-select ref="selectRef"  :features="selectedFeatures" @select="handleSelect" :condition="selectCondition"><ol-style :overrideStyleFunction="selectStyleFunc"> </ol-style></ol-interaction-select></ol-map><div class="toolbar"><el-button type="primary" @click="handleClick">{{ drawFlag ? '结束' : '开始' }}绘制</el-button><el-button type="warning" :disabled="!drawFlag" @click="handleCancelClick">撤销上步</el-button></div>
</template><script setup lang="ts">
import { Collection } from 'ol';
import { FeatureLike } from 'ol/Feature';
import { LineString, Point } from 'ol/geom';
import { DrawEvent } from 'ol/interaction/Draw';
import { Circle, Fill, Stroke, Style } from 'ol/style';
const center = ref([121, 31]);
const projection = ref('EPSG:4326');
const zoom = ref(5);
const rotation = ref(0);
const features = ref(new Collection()); //保存绘制的features
const selectedFeatures = ref(new Collection()); //保存绘制的features
const source = ref([]);
const mapRef = ref();
const drawRef = ref();
const selectRef = ref();
const modifyRef = ref();
const drawFlag = ref(false);
const modifyFlag = ref(false);
const selectConditions = inject('ol-selectconditions');const selectCondition = selectConditions.click;onMounted(() => {drawRef.value.draw.setActive(false);// modifyRef.value.modify.setActive(false);
});const drawstart = (event: Event) => {console.log(event);
};const drawend = (event: DrawEvent) => {console.log(event.feature.getGeometry());
};const handleClick = () => {drawFlag.value = !drawFlag.value;drawRef.value.draw.setActive(drawFlag.value);modifyFlag.value=!drawFlag.value;// modifyRef.value.modify.setActive(!drawFlag.value);selectRef.value.select.setActive(!drawFlag.value);selectRef.value.select.getFeatures().clear();
};
const handleCancelClick = () => {drawRef.value.draw.removeLastPoint();
};const handleSelect = e => {// modifyRef.value.modify.setActive(false);modifyFlag.value=false;if (!e.selected.length) {selectedFeatures.value.clear();selectRef.value.select.getFeatures().clear();} else {nextTick(()=>{modifyFlag.value=true;// modifyRef.value?.modify.setActive(true);selectedFeatures.value=e.target.getFeatures();})}
};const handleStyleFunction = (feature: FeatureLike, currentStyle: Style) => {const geometry = feature.getGeometry();const coord = geometry.getCoordinates();const type = geometry.getType();const styles: Array<Style> = [];if (type === 'LineString') {for (let i = 0; i < coord.length - 1; i++) {styles.push(new Style({geometry: new LineString([coord[i], coord[i + 1]]),stroke: new Stroke({color: 'orange',lineDash: coord.length > 2 && i < coord.length - 2 ? [] : [10],width: 2})}));}}return styles;
};const handleInsertVertexCondition = e => {return false;
};const handleModifyStyleFunction = (feature: FeatureLike, currentStyle: Style) => {const coord = feature.getGeometry().getCoordinates();const layer = mapRef.value.map.getLayers().item(0);const features = layer.getSource().getFeatures();const coords = features.map(feature => feature.getGeometry().getCoordinates()).flat(2);let style = undefined;// 只有鼠标在顶点时才能触发编辑功能if (coords.find(c => c.toString() === coord.toString())) {style = new Style({geometry: new Point(coord),image: new Circle({radius: 6,fill: new Fill({color: '#ffff'}),stroke: new Stroke({color: 'red',width: 2})})});}return style;
};const handleModifyEnd = e => {features.value.push(e.feature); //这里可以把编辑后的feature添加到layer绑定的features中console.log('modifyend', e.features);
};const styleFunction = (feature: FeatureLike, currentStyle: Style) => {const styles = [];styles.push(new Style({fill: new Fill({color: [128, 128, 255, 0.5]}),stroke: new Stroke({color: 'blue',width: 2})}));return styles;
};const selectStyleFunc = feature => {const styles = [];const coord = feature.getGeometry().getCoordinates().flat(1);for (let i = 0; i < coord.length - 1; i++) {styles.push(new Style({geometry: new Point(coord[i]),image: new Circle({radius: 4,fill: new Fill({color: '#ffff'}),stroke: new Stroke({color: 'orange',width: 2})})}));}styles.push(new Style({stroke: new Stroke({color: 'orange',width: 2}),fill: new Fill({color: '#ffff'})}));return styles;
};
</script>
<style scoped lang="scss">
.toolbar {position: absolute;top: 20px;left: 100px;
}
</style>