<div :class="2 == 1 ? 'left' : 2 == 2 ? 'left center' : 'left right'" style="backgroundColor: rgba(74, 204, 64, 0.25)">

这是一个Vue.js的代码片段，其中使用了三元运算符来根据条件设置CSS类。如果条件2等于1，则该元素将具有“left”类，否则如果条件2等于2，则该元素将具有“left center”类，否则将具有“left right”类。此外，该元素的背景颜色设置为RGBA值（74, 204, 64, 0.25）的半透明绿色。

相关问题

在vue2中怎么使用cesium,自己手动绘制点线面功能

你可以使用Cesium的Vue组件来集成Cesium到Vue 2中。首先，你需要安装Cesium和VueCesium组件:

1. 安装Cesium: 可以从官网下载或使用npm安装。

npm install cesium --save

2. 安装VueCesium:

npm install vue-cesium --save

3. 在Vue组件中使用Cesium:

a. 引用Cesium和VueCesium：

import * as Cesium from "cesium";
import VueCesium from "vue-cesium";

b. 注册VueCesium：

  Vue.use(VueCesium, {
    // 版本号，对应Cesium.js的版本号
    cesiumPath: '/static/Cesium/Cesium.js',
    // 在启动VueCesium的时候自动注入Cesium对象
    // 如果不注入，需要通过this.$Cesium调用
    // 如果单独在组件中使用
    // this.$Cesium  === Cesium
    // 如果在Vue mixin中使用
    // Vue.prototype.$Cesium === Cesium
    // 如果在常规JavaScript文件或者函数中使用
    // import Cesium from 'cesium/Cesium'
  });

c. 在Vue组件中使用Cesium：

  <template>
    <div>
      <!-- 根据组件的命名规则，直接在组件中使用cesium视图，并增加cesium属性，支持覆盖默认的配置 -->
      <cesium-viewer ref="cesiumViewer" :cesium-prop="cesiumOptions"></cesium-viewer>
    </div>
  </template>

  <script>
  export default {
    name: 'cesium-demo',
    data() {
      return {
        cesiumOptions: {
          ///... One of the cesium viewer options
        }
      };
    },
    mounted() {
      // Accessing cesium viewer instance
      console.log(this.$refs.cesiumViewer.cesium.viewer);
    },

    methods: {
      // 方法可以直接在组件中定义并调用
    }
  };
  </script>

  <style scoped>
  </style>

d. 自己手动绘制点线面功能：

<template>
  <div>
    <cesium-viewer ref="cesiumViewer" @connected="createEntities()" style="height: 100%; width: 100%" :cesium-prop="cesiumOptions"></cesium-viewer>
  </div>
</template>

<script>
import * as Cesium from "cesium";

export default {
  name: "cesium-demo",
  data() {
    return {
      cesiumOptions: {
        terrainProviderViewModels: [],
        terrainProvider: new Cesium.EllipsoidTerrainProvider(),
        mapProjection: new Cesium.WebMercatorProjection(),
        baseLayerPicker: false,
        geocoder: false,
        homeButton: false,
        sceneModePicker: false,
        navigationHelpButton: false,
        animation: false,
        timeline: false,
      },
      viewer: null,
      clickHandler: null,
      drawingHandler: null,
      measurementLabel: "",
      measurementEntity: null,
      drawingPolyline: null,
      drawingPolygon: null,
    };
  },
  methods: {
    createEntities() {
      this.viewer = this.$refs.cesiumViewer.cesium.viewer;
      this.clickHandler = new Cesium.ScreenSpaceEventHandler(this.viewer.scene.canvas);
      this.createDrawingHandler();
    },
    createDrawingHandler() {
      this.drawingHandler = new Cesium.ScreenSpaceEventHandler(this.viewer.scene.canvas);

      let positions = [];
      let drawingMode = null;
      let label = null;

      const finishDrawing = function () {
        let entity = null;
        if (drawingMode === "POLYLINE") {
          entity = this.viewer.entities.add({
            polyline: {
              positions: positions,
              width: 3,
              material: Cesium.Color.BLUE,
            },
          });
        } else if (drawingMode === "POLYGON") {
          entity = this.viewer.entities.add({
            polygon: {
              hierarchy: positions,
              height: 0,
              material: Cesium.Color.BLUE.withAlpha(0.5),
              outline: true,
              outlineColor: Cesium.Color.BLACK,
            },
          });
        }

        if (entity) {
          entity.description =
            '<div class="cesium-info-box"><p>' + this.measurementLabel + "</p></div>";

          if (this.measurementEntity) {
            this.viewer.entities.remove(this.measurementEntity);
          }
          this.measurementEntity = entity;
        }

        this.clearDrawing();
      }.bind(this);

      const clearDrawing = function () {
        drawingMode = null;

        if (this.measurementEntity) {
          this.viewer.entities.remove(this.measurementEntity);
          this.measurementEntity = null;
        }

        if (label) {
          label.show = false;
          label = null;
          this.measurementLabel = "";
        }

        if (this.drawingPolyline) {
          this.viewer.entities.remove(this.drawingPolyline);
          this.drawingPolyline = null;
        }

        if (this.drawingPolygon) {
          this.viewer.entities.remove(this.drawingPolygon);
          this.drawingPolygon = null;
        }

        positions = [];
      }.bind(this);

      this.clickHandler.setInputAction((click) => {
        const position = this.viewer.scene.pickPosition(click.position);
        if (Cesium.defined(position) && drawingMode) {
          positions.push(position);

          if (drawingMode === "POLYLINE") {
            if (this.drawingPolyline) {
              this.viewer.entities.remove(this.drawingPolyline);
            }
            this.drawingPolyline = this.viewer.entities.add({
              polyline: {
                positions: positions,
                width: 3,
                material: Cesium.Color.BLUE,
              },
            });
          }

          if (drawingMode === "POLYGON") {
            if (positions.length === 2) {
              if (this.drawingPolygon) {
                this.viewer.entities.remove(this.drawingPolygon);
              }
              this.drawingPolygon = this.viewer.entities.add({
                polygon: {
                  hierarchy: new Cesium.CallbackProperty(() => {
                    if (this.viewer.scene.mode !== Cesium.SceneMode.MORPHING) {
                      return new Cesium.PolygonHierarchy(positions);
                    }
                  }, false),
                  material: Cesium.Color.BLUE.withAlpha(0.5),
                  height: 0,
                  outline: true,
                  outlineColor: Cesium.Color.WHITE,
                },
              });
            } else if (positions.length > 2) {
              this.viewer.entities.remove(this.drawingPolygon);
              this.drawingPolygon = this.viewer.entities.add({
                polygon: {
                  hierarchy: new Cesium.CallbackProperty(() => {
                    if (this.viewer.scene.mode !== Cesium.SceneMode.MORPHING) {
                      return new Cesium.PolygonHierarchy(positions);
                    }
                  }, false),
                  material: Cesium.Color.BLUE.withAlpha(0.5),
                  height: 0,
                  outline: true,
                  outlineColor: Cesium.Color.WHITE,
                },
              });
            }
          }
        }
      }, Cesium.ScreenSpaceEventType.LEFT_CLICK);

      this.clickHandler.setInputAction(() => {
        this.viewer.scene.screenSpaceCameraController.enableLook = false;
      }, Cesium.ScreenSpaceEventType.RIGHT_DOWN);

      this.clickHandler.setInputAction(() => {
        this.viewer.scene.screenSpaceCameraController.enableLook = true;
      }, Cesium.ScreenSpaceEventType.RIGHT_UP);

      this.drawingHandler.setInputAction(() => {
        finishDrawing();
      }, Cesium.ScreenSpaceEventType.LEFT_DOUBLE_CLICK);

      document.onkeyup = (arg) => {
        if (arg.keyCode == 27) {
          clearDrawing();
          this.drawingHandler.removeInputAction(Cesium.ScreenSpaceEventType.LEFT_CLICK);
          this.drawingHandler.removeInputAction(Cesium.ScreenSpaceEventType.LEFT_DOUBLE_CLICK);
        }
      };

      // Set up drawing toolbar
      const drawingToolbar = document.getElementById("drawingToolbar");

      document.getElementById("polylineButton").addEventListener(
        "click",
        function () {
          clearDrawing();
          drawingMode = "POLYLINE";
          this.measurementLabel = "Distance";
          this.addToolbarLabel("Click to start drawing a line.");
        }.bind(this)
      );

      document.getElementById("polygonButton").addEventListener(
        "click",
        function () {
          clearDrawing();
          drawingMode = "POLYGON";
          this.measurementLabel = "Area";
          this.addToolbarLabel("Click to start drawing a polygon.");
        }.bind(this)
      );

      document.getElementById("clearButton").addEventListener(
        "click",
        function () {
          clearDrawing();
          this.drawingHandler.removeInputAction(Cesium.ScreenSpaceEventType.LEFT_CLICK);
          this.drawingHandler.removeInputAction(Cesium.ScreenSpaceEventType.LEFT_DOUBLE_CLICK);
        }.bind(this)
      );
    },
    addToolbarLabel: function (text) {
      const toolbarLabel = document.getElementById("drawingToolbarLabel");
      toolbarLabel.innerHTML = text;

      if (label) {
        label.show = false;
        label = null;
      }

      label = this.viewer.entities.add({
        position: Cesium.Cartesian3.fromArray(positions),
        label: {
          text: text,
          font: "16px sans-serif",
          pixelOffset: new Cesium.Cartesian2(0.0, 20),
          showBackground: true,
          backgroundColor: new Cesium.Color.fromCssColorString("#333333").withAlpha(0.7),
          disableDepthTestDistance: Number.POSITIVE_INFINITY,
        },
      });
    },
  },
  beforeDestroy() {
    this.viewer = this.$refs.cesiumViewer.cesium.viewer;
    this.clickHandler.destroy();
    this.drawingHandler.destroy();
  },
};
</script>

<style scoped>
  #drawingToolbar {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    padding: 10px;
    height: 50px;
    background: rgba(255, 255, 255, 0.8);
    border-bottom: 1px solid gray;
    z-index: 9999;
    display: flex;
    justify-content: space-between;
    align-items: center;
  }

  #clearButton {
    margin-left: auto;
  }

  .cesium-info-box p {
    margin: 0;
    color: white;
  }
</style>

以上代码提供了简单的使用Cesium在Vue 2中手动绘制点线面功能。

鼠标略过白色方框选项时，为每一个选项添加与头部导航栏相同的背景颜色，同时设置字体颜色为白色；尽可能与图片效果保持一致。功能要求：①鼠标略出头像及白色方框区域时，白色方框消失；②头像右侧显示存储在本地存储中的用户名称，③点击退出登录，清除在本地存储中的数据并跳转到登陆页面。

以下是实现该功能的代码示例：

HTML代码：

<header>
  <div class="logo"></div>
  <div class="user">
    <div class="avatar"></div>
    <div class="username"></div>
    <div class="options">
      <div class="option">选项1</div>
      <div class="option">选项2</div>
      <div class="option">选项3</div>
      <div class="option">选项4</div>
      <div class="logout">退出登录</div>
    </div>
  </div>
</header>

CSS代码：

header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background-color: #f7f7f7;
  padding: 20px;
}

.logo {
  width: 50px;
  height: 50px;
  background-image: url("logo.png");
  background-size: cover;
  background-position: center;
}

.user {
  display: flex;
  align-items: center;
  position: relative;
}

.avatar {
  width: 40px;
  height: 40px;
  background-image: url("avatar.png");
  background-size: cover;
  background-position: center;
  border-radius: 50%;
  cursor: pointer;
}

.username {
  margin-left: 10px;
  font-size: 16px;
  font-weight: bold;
}

.options {
  display: none;
  position: absolute;
  top: 50px;
  right: 0;
  width: 150px;
  background-color: #f7f7f7;
  box-shadow: 0 0 5px rgba(0, 0, 0, 0.2);
  z-index: 999;
}

.option {
  padding: 10px;
  cursor: pointer;
}

.option:hover {
  background-color: #007bff;
  color: #fff;
}

.logout {
  padding: 10px;
  cursor: pointer;
  background-color: #dc3545;
  color: #fff;
}

.logout:hover {
  background-color: #c82333;
}

JavaScript代码：

// 获取相关元素
const avatar = document.querySelector(".avatar");
const options = document.querySelector(".options");
const optionList = document.querySelectorAll(".option");
const logout = document.querySelector(".logout");
const username = document.querySelector(".username");

// 鼠标移入头像时显示选项菜单
avatar.addEventListener("mouseover", function() {
  options.style.display = "block";
});

// 鼠标移出头像和选项菜单时隐藏选项菜单
avatar.addEventListener("mouseout", function() {
  options.style.display = "none";
});

options.addEventListener("mouseover", function() {
  options.style.display = "block";
});

options.addEventListener("mouseout", function() {
  options.style.display = "none";
});

// 鼠标移入选项时改变背景颜色和字体颜色
optionList.forEach(function(option) {
  option.addEventListener("mouseover", function() {
    option.style.backgroundColor = "#007bff";
    option.style.color = "#fff";
  });
  
  option.addEventListener("mouseout", function() {
    option.style.backgroundColor = "transparent";
    option.style.color = "#000";
  });
});

// 点击退出登录时清除本地存储并跳转到登录页面
logout.addEventListener("click", function() {
  localStorage.clear();
  window.location.href = "login.html";
});

// 从本地存储中获取用户名并显示
const storedUsername = localStorage.getItem("username");
if (storedUsername) {
  username.textContent = storedUsername;
}