移动在线缓存
一.在线缓存的必要性
众所周知，移动一张图目前包含两个应用场景：在线和离线。在线场景中，多用户共用数据，与云服务同步，实时性较强。而后者为单用户使用数据，无实时性要求，不常更新，需要数据拷贝，数据也能保证一定的隐秘性。那么在线缓存的应用场景突出在哪里呢？
###1.在线离线一体化
目前移动一张图的在线离线需要在登录时用户手动切换。而数据方面二者并不是同步的，在数据管理方面存在一定的弊端。而通过在线缓存即可实现多用户同步数据，具有较强的数据实时性,数据也便于云端管理。
###2. 方便用户操作。
用户在在线与离线的应用场景中可以自由切换,比如在线过程中，临时切换，并不需要返回登录页面切换。
但同时，部分用户需要保证数据安全性（不需要在线版）,或者大部分使用场景都是离线,所以我们并不能将离线场景去除。
综述,在线、离线、在线缓存为3大应用场景。
二.在线缓存的可行性
目前我们一张图主要数据有两类：地图数据和业务数据。而 ArcGIS for desktop 10.2.2以上已经支持两者缓存的技术可行性。具体条件如下：
- ArcGIS for desktop 版本为10.2.2或者 以上。
- 相关服务需要配置好设置(具体见后文)
- AGS-Runtime-SDK-iOS 10.2.5
- 业务数据需要通过Feature Service服务.
三. 支持在线缓存的服务设置
- 设置允许客户端导出切片
- 设置允许切片导出限制
- 发布 Feature Service 服务
四. iOS相关API与代码
相关类与方法
AGSExportTileCacheTaskAGSExportTileCacheParamsAGSGDBSyncTaskAGSGDBGenerateParametersexportTileCacheWithParametersestimateTileCacheSizeWithParametersgenerateGeodatabaseWithParameters
初始化底图与要素
let huaianServiceUrl = "http://192.168.1.162:6080/arcgis/rest/services/test3/MapServer"
let huaianFeatureUrl = "http://192.168.1.162:6080/arcgis/rest/services/test4/FeatureServer"
class ViewController: UIViewController,AGSLayerDelegate {
@IBOutlet var mapView: AGSMapView!
var mapLayer: AGSTiledMapServiceLayer!
var tileCacheTask: AGSExportTileCacheTask!
var gdbTask: AGSGDBSyncTask!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
self.mapLayer = AGSTiledMapServiceLayer(URL: NSURL(string: huaianServiceUrl))
self.mapLayer.delegate = self
mapView.addMapLayer(mapLayer)
if self.tileCacheTask == nil {
self.tileCacheTask = AGSExportTileCacheTask(URL: NSURL(string: huaianServiceUrl))
}
}
func layerDidLoad(layer: AGSLayer!) {
if layer == self.mapLayer {
gdbTask = AGSGDBSyncTask(URL: NSURL(string: huaianFeatureUrl))
gdbTask.loadCompletion = {
error in
if error != nil {
print(error.localizedDescription)
}
for info in self.gdbTask.featureServiceInfo.layerInfos as! [AGSMapServiceLayerInfo] {
let url = self.gdbTask.URL.URLByAppendingPathComponent("\(info.layerId)")
let featureServiceTable = AGSGDBFeatureServiceTable(serviceURL: url, credential: self.gdbTask.credential, spatialReference: self.mapView.spatialReference)
let featureLayer = AGSFeatureTableLayer(featureTable:featureServiceTable)
self.mapView.addMapLayer(featureLayer)
}
}
}
}
下载底图形成tpk文件
@IBAction func downloadTpkAction(sender: UIBarButtonItem) {
SVProgressHUD.showWithStatus("准备下载")
let levels = [self.mapLayer.currentLOD().level]
let extent = self.mapView.visibleAreaEnvelope
//let extent = AGSEnvelope(xmin: 610875.41170353664, ymin: 3780046.638612428, xmax: 610948.9641964633, ymax: 3780074.6404850003, spatialReference: self.mapView.spatialReference)
let params = AGSExportTileCacheParams(levelsOfDetail: levels, areaOfInterest: extent)
//showSizesOfTpk(params)
downloadTileCache(params)
}
func downloadTileCache(params: AGSExportTileCacheParams) {
let tpkPath = NSHomeDirectory() + "/Documents" + "/tpk"
self.tileCacheTask.exportTileCacheWithParameters(params, downloadFolderPath: tpkPath, useExisting: true, status: { (status, userInfo) in
print("\(AGSResumableTaskJobStatusAsString(status)), \(userInfo)")
let totalBytesDownloaded: AnyObject? = userInfo?["AGSDownloadProgressTotalBytesDownloaded"]
let totalBytesExpected: AnyObject? = userInfo?["AGSDownloadProgressTotalBytesExpected"]
if totalBytesDownloaded != nil && totalBytesExpected != nil {
let dPercentage = Float(totalBytesDownloaded! as! NSNumber)/Float(totalBytesExpected! as! NSNumber)
SVProgressHUD.showProgress(dPercentage, status: "下载中")
if dPercentage == 1 {
SVProgressHUD.dismiss()
}
print(dPercentage)
} }) { (tiledLayer, error) in
if error != nil {
SVProgressHUD.showErrorWithStatus(error.localizedDescription)
}
self.mapView.reset()
self.mapView.addMapLayer(tiledLayer, withName:"offline")
}
}
###下载要素形成 gdb
@IBAction func downloadGdbAction(sender: UIBarButtonItem) {
SVProgressHUD.showWithStatus("准备下载")
let gdbPath = NSHomeDirectory() + "/Documents" + "/gdb"
let params = AGSGDBGenerateParameters(featureServiceInfo: self.gdbTask.featureServiceInfo)
params.extent = self.mapView.maxEnvelope
params.outSpatialReference = self.mapView.spatialReference
let layers = self.gdbTask.featureServiceInfo.layerInfos.map { layerInfo -> Int in layerInfo.layerId
}
params.layerIDs = layers
self.gdbTask.generateGeodatabaseWithParameters(params, downloadFolderPath: gdbPath, useExisting: true, status: {
(status, userInfo) in
print(AGSResumableTaskJobStatusAsString(status))
let totalBytesDownloaded: AnyObject? = userInfo?["AGSDownloadProgressTotalBytesDownloaded"]
let totalBytesExpected: AnyObject? = userInfo?["AGSDownloadProgressTotalBytesExpected"]
if totalBytesDownloaded != nil && totalBytesExpected != nil {
let dPercentage = Float(totalBytesDownloaded! as! NSNumber)/Float(totalBytesExpected! as! NSNumber)
SVProgressHUD.showProgress(dPercentage, status: "下载中")
if dPercentage == 1 {
SVProgressHUD.dismiss()
}
print(dPercentage)
}
}) { (gdb, error) in
if error != nil {
print(error)
}
for layer in self.mapView.mapLayers as! [AGSLayer] {
if layer is AGSFeatureTableLayer {
self.mapView.removeMapLayer(layer)
}
}
if gdb.featureTables().count > 0 {
for table in gdb.featureTables() as! [AGSFeatureTable]{
if table.hasGeometry() {
let tableLayer = AGSFeatureTableLayer(featureTable: table)
self.mapView.addMapLayer(tableLayer)
}
} }
}
}
五. 总结与后续问题思考
经过研究实践，移动在线缓存技术是完全可行的,详见 CacheDemo