學習cesium，關於圖層界面的切換

最近學習cesium的3D引擎，有關圖層切換的例子比較少，在官網上看見了一些例子加以自己的理解。投機了一種近似於圖層切換的效果。

這種圖層切換每次點擊按鈕時，會把其他的數據和實體給刪除。然後再創建或載入一個新的

閑話不多說我們直接上代碼

Sandcastle.addToolbarButton('Basic styling', function() {
                viewer.dataSources.add(Cesium.GeoJsonDataSource.load(URL, {
                    stroke: Cesium.Color.HOTPINK,
                    fill: Cesium.Color.PINK.withAlpha(0.5),
                    strokeWidth: 3
                }));
            });
            Sandcastle.addToolbarButton('按鈕',function() {

                var position = Cesium.Cartesian3.fromDegrees(116.39053344726561,39.89604077881996, 0.0);
                var hpr = new Cesium.HeadingPitchRoll(Cesium.Math.toRadians(135), 0.0, 0.0);
                var orientation = Cesium.Transforms.headingPitchRollQuaternion(position, hpr);

                var model = viewer.entities.add({
                    id:'01',
                    position : position,
                    orientation : orientation,
                    model : {
                        uri : URL,
                        minimumPixelSize : 128,
                        maximumScale : 20000
                    }
                });

   
            },"toolbar");

            Sandcastle.reset = function() {
                viewer.dataSources.removeAll();
                viewer.entities.removeById('01')//根據id刪除entity

                //設置相機為home為起點
                viewer.camera.lookAt(Cesium.Cartesian3.fromDegrees(116.39053344726561,39.89604077881996, 2631.082799425431), new Cesium.Cartesian3(0.0, -4790.0, 3930.0));
                viewer.camera.lookAtTransform(Cesium.Matrix4.IDENTITY);
            };

//Sandcastle_End
            Sandcastle.finishedLoading();