tooltip实现方式主要分两种：entity和div。

entity：基于cesium提供的entity接口

优点：地球放大、缩小或移动，位置也会跟着变化；显示灵活，无鼠标悬浮上面丢失焦点的bug
缺点：展示的信息不能是html格式，只能是文本；遮挡问题

div：基于悬浮的div控件

优点：展示的信息可以是html格式；无遮挡问题
缺点：地球放大、缩小或移动，位置不会跟着变化；有鼠标悬浮上面丢失焦点的bug

今天介绍基于entity方式：

//封装TooltipCesium对象
var TooltipCesium = (function () {
    var isInit = false;
    var viewer;
    var labelEntity;
 
    function _() { };
 
    _.initTool = function (_viewer) {
        if (isInit) { return; }
        viewer = _viewer;
        labelEntity = viewer.entities.add({
            position: Cesium.Cartesian3.fromDegrees(0, 0),
            label: {
                text: '提示',
                font: '15px sans-serif',
                pixelOffset: new Cesium.Cartesian2(8, 8),//y大小根据行数和字体大小改变
                horizontalOrigin: Cesium.HorizontalOrigin.LEFT,
                showBackground: true,
                backgroundColor: new Cesium.Color(0.165, 0.165, 0.165, 1.0)
            }
        });
        labelEntity.show = false;
        isInit = true;
    };
 
    _.setVisible = function (visible) {
        if (!isInit) { return; }
        labelEntity.show = visible ? true : false;
    };
 
   
    _.showAt = function (position, message) {
        if (!isInit) { return; }
        if (position && message) {
            labelEntity.show = true;
            var cartesian = viewer.camera.pickEllipsoid(position, viewer.scene.globe.ellipsoid);// 
            if (cartesian) {
                labelEntity.position = cartesian;
                labelEntity.show = true;
                labelEntity.label.text = message;
            } else {
                labelEntity.show = false;
            }
        }
    };
 
   
    _.showAtCartesian = function (cartesian, message) {
        if (!isInit) { return; }
        if (cartesian && message) {
            labelEntity.show = true;
            labelEntity.position = cartesian;
            labelEntity.show = true;
            labelEntity.label.text = message;
        }
    };
    return _;
})();


var viewer = new Cesium.Viewer('cesiumContainer',{
    baseLayerPicker:false,
    imageryProvider: new Cesium.UrlTemplateImageryProvider({
        url:'http://localhost:8080/xyz/Satellite_24459/{z}/{x}/{y}.jpg'
    })
});

var scene = viewer.scene;
var handler = new Cesium.ScreenSpaceEventHandler(scene.canvas);
var ellipsoid = scene.globe.ellipsoid; 
var cartesian = null;

TooltipCesium.initTool(viewer);


 //监听鼠标单击事件
handler.setInputAction(function (movement) {
    cartesian = viewer.camera.pickEllipsoid(movement.position, ellipsoid);
    if (cartesian) {
        TooltipCesium.showAt(movement.position, '要展示的信息');
        // TooltipCesium.showAtCartesian(cartesian, '要展示的信息');
    } else {
        TooltipCesium.setVisible(false);
    }
}, Cesium.ScreenSpaceEventType.LEFT_CLICK);

image.png