openlayers 绘图功能，编辑多边形，select，snap组件的使用（五）

本篇介绍一下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 openlayers 中 draw，select，snap，modify 功能的使用

3 实现

<template>
  <div id="map" class="map"></div>
  <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, Feature, Map, View } from 'ol';
import { get } from 'ol/proj';
import { Style } from 'ol/style';
import { Draw, Modify, Select, Snap } from 'ol/interaction.js';
import { Vector as VectorSource } from 'ol/source.js';
import { Vector as VectorLayer } from 'ol/layer.js';
import { Circle, Fill, Stroke } from 'ol/style.js';
import { LineString, Point, Polygon } from 'ol/geom';

const projection = get('EPSG:4326');
const source = new VectorSource({ wrapX: false });
const map = shallowRef();
const draw = shallowRef();
const modify = shallowRef();
const select = shallowRef();
const snap = shallowRef();
const features = ref(new Collection());//保存绘制的features
const drawFlag = ref(false);

onMounted(() => {
  initMap();
  initInteraction();
});



const initMap = () => {
  map.value = new Map({
    target: 'map',
    view: new View({
      center: [116.406393, 39.909006],
      projection: projection,
      zoom: 5
    }),
    layers: [
      new VectorLayer({
        source: source,
        style: styleFunc
      })
    ]
  });
};

const initInteraction = () => {
  draw.value = new Draw({
    active: false,
    features: features.value,
    source: source,
    type: 'Polygon',
    style: drawStyleFunc
  });
  draw.value.on('drawstart', e => {
    console.log('e', e);
  });
  draw.value.on('drawend', e => {
    console.log('features.value', features.value);
    console.log('coord', e.feature.getGeometry().getCoordinates());
  });
  map.value.addInteraction(draw.value);
  draw.value.setActive(false);

  select.value = new Select({
    style: selectStyleFunc
  });

  select.value.on('select', e => {
			modify.value.setActive(true);
  });

  map.value.addInteraction(select.value);
  select.value.setActive(false);


  modify.value = new Modify({
    features: select.value.getFeatures(), // Modify 将处理 Select 交互所选的要素
    pixelTolerance: 10, //设置吸附像素值
    insertVertexCondition: handleInsertVertexCondition,
    style: modifyStyleFunc
  });

  modify.value.on('modifystart', event => {});

  modify.value.on('modifyend', event => {
		console.log('modifyend', event.features);
  });

  map.value.addInteraction(modify.value);
  modify.value.setActive(false);
	// 用于处理绘制或者编辑多边形时，与已经存在图形的自动吸附，如下是只吸附顶点，不媳妇边
  snap.value = new Snap({
		source:source,
		edge:false,//不吸附边
	});
	map.value.addInteraction(snap.value);
};

const handleClick = () => {
  drawFlag.value = !drawFlag.value;
  draw.value.setActive(drawFlag.value);
  select.value.setActive(!drawFlag.value);
  modify.value.setActive(!drawFlag.value);
	select.value.getFeatures().clear();
};
const handleCancelClick = () => {
  draw.value.removeLastPoint();
};

const drawStyleFunc = feature => {
  const styles = [];
  const type = feature.getGeometry().getType();
  const coord = feature.getGeometry().getCoordinates();
  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 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;
};

const modifyStyleFunc = feature => {
  const coord = feature.getGeometry().getCoordinates();
  const layer = map.value.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 handleInsertVertexCondition = e => {
  // 点击或者拖动边时不插入新顶点
  return false;
};
const styleFunc = feature => {
  const styles = [];
  styles.push(
    new Style({
      fill: new Fill({
        color: [128, 128, 255, 0.5]
      }),
      stroke: new Stroke({
        color: 'blue',
        width: 2
      })
    })
  );
  return styles;
};
</script>
<style scoped lang="scss">
.map {
  width: 100%;
  height: 100%;
  background: #000;
}
.toolbar {
  position: absolute;
  top: 20px;
  left: 100px;
}
</style>