说明：  读取shape文件，实现放大缩小漫游全图显示，并对图层进行上移下移删除操作，查询要素信息，并完成点密度、唯一值渲染
(Read the shape file, realize the zoom and wander full map display, move the layer up and down, delete the operation, query the element information, and finish the point density and the unique value rendering)