A mixin which adds default drag and drop support for CZML files to the Viewer widget.
Rather than being called directly, this function is normally passed as
a parameter to
Viewer#extend, as shown in the example below.示例：
// Add basic drag and drop support and pop up an alert window on error.
var viewer = new Cesium.Viewer('cesiumContainer');
viewer.extend(Cesium.viewerDragDropMixin);
viewer.dropError.addEventListener(function(viewerArg, source, error) {
window.alert('Error processing ' + source + ':' + error);
});成员变量
clampToGround : Boolean
Gets or sets a value indicating if the datasources should be clamped to the ground
clearOnDrop : Boolean
Gets or sets a value indicating if existing data sources should be cleared before adding the newly dropped sources.
dropEnabled : Element
Gets or sets a value indicating if drag and drop support is enabled.
dropError : Event
Gets the event that will be raised when an error is encountered during drop processing.
dropTarget : Element
Gets or sets the element to serve as the drop target.
flyToOnDrop : Boolean
Gets or sets a value indicating if the camera should fly to the data source after it is loaded.
Gets or sets the proxy to be used for KML.
