我一直在将图像从我的无人机直接下载到我的应用程序时遇到一些问题。我在尝试下载图像时不断收到“系统忙，请稍后重试。（代码：-1004） ”错误消息，我已在 stackoverflow 上查看了 DJI 论坛和其他问题，但未能找到任何解决方案到这个问题。
我已经看过这个问题，但我已经在使用该答案中建议的技术。
这是我为下载图像而编写的函数：
func downloadFilesFromDrone(){
// get current product
guard let drone = DJISDKManager.product() else {
Logger.logError("Product is connected but DJISDKManager.product is nil when attempting to download media")
return
}
// Get camera on drone
guard let camera: DJICamera = drone.camera else {
Logger.logError("Unable to detect Camera in downloadFilesFromDrone()")
// make recursive call until we are able to detect the camera
DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
Logger.logH1("Trying to detect Camera again")
self.downloadFilesFromDrone()
}
return
}
Logger.logH1("Successfully detected the camera")
// check if we can download images with the product
if !camera.isMediaDownloadModeSupported() {
Logger.logError("Product does not support media download mode")
return
}
// switch camera mode to allow for media downloads
camera.setMode( .mediaDownload, withCompletion: {(error) in
if error != nil {
print("\(error!.localizedDescription)")
}
else {
// get the media manager from the drone to gain access to the files
let manager = camera.mediaManager!
manager.refreshFileList(completion: { (error) in
if error != nil {
print("State: \(manager.fileListState.rawValue)")
print("Error refreshing list: \(error!.localizedDescription)")
}
else {
Logger.logH1("Refreshed file list")
print("State: \(manager.fileListState.rawValue)")
guard let files = manager.fileListSnapshot() else {
Logger.logError("No files to download")
return
}
Logger.logH1("There are files to download")
var images: [UIImage] = []
for file in files {
if file.mediaType == .JPEG {
print("Time created: \(file.timeCreated)")
DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
file.fetchData(withOffset: 0, update: DispatchQueue.main, update: {(_ data: Data?, _ isComplete: Bool, _ error: Error?) -> Void in
if error != nil {
print("State: \(manager.fileListState.rawValue)")
print("Error downloading photo: \(error!)")
}
else {
// unwrap downloaded data and create image
if let data = data, let downloadedImage = UIImage(data: data) {
print("Image was downloaded!")
images.append( downloadedImage )
}
}
}) // end of filedata fetch
}
}
} // end of loop
}
}) // end of file-refresh block
}
})// end of camera setMode block
}
这是用我的无人机测试时这个函数的输出：
*** Product Connected ***
*** Unable to detect Camera in downloadFilesFromDrone() ***
*** Firmware package version is: Unknown ***
--> Trying to detect Camera again
--> Successfully detected the camera
--> Refreshed file list
State: 0
--> There are files to download
Time created: 2017-09-01 15:17:04
Time created: 2017-09-01 15:17:16
Time created: 2017-09-01 15:17:26
Time created: 2017-09-01 15:17:36
Time created: 2017-09-01 15:19:06
State: 0
Error downloading photo: System is busy, please retry later.(code:-1004)
State: 0
Error downloading photo: System is busy, please retry later.(code:-1004)
State: 0
Error downloading photo: System is busy, please retry later.(code:-1004)
State: 0
Error downloading photo: System is busy, please retry later.(code:-1004)
编辑：
下面是我用来从无人机下载图像的代码。
/**
* This function downloads the N latest images from the drone and passes them to the completionhandler once all images have completed downloading
*/
func downloadImages( files: [DJIMediaFile], howMany: Int, maxErrors: Int, completion: @escaping ([UIImage]) -> Void){
Logger.logH1("Queueing \(howMany) image(s) to be downloaded")
func downloadNextImage( files: [DJIMediaFile], fileCount: Int, index: Int = 0, downloadedFiles: [UIImage] = [], errorCount: Int = 0) {
// stop when we reach the end of the list
if index == fileCount {
completion(downloadedFiles)
return
}
else {
var imageData: Data?
let file = files[index]
file.fetchData(withOffset: 0, update: DispatchQueue.main, update: {(_ data: Data?, _ isComplete: Bool, _ error: Error?) -> Void in
if let error = error {
Logger.logError("\(error)")
if errorCount < maxErrors {
DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
Logger.logH1("Attempting to download: \(file.fileName) again")
downloadNextImage(files: files, fileCount: fileCount, index: index, downloadedFiles: downloadedFiles, errorCount: errorCount + 1)
}
}
else {
Logger.logError("Too many errors downloading the images, try downloading again")
}
}
else {
// if image is done downloading
if isComplete {
// get full image data
if let imageData = imageData, let image = UIImage(data: imageData) {
Logger.logH1("Downloaded: \(file.fileName)")
// now that the image is done downloading, move onto the next image
downloadNextImage(files: files, fileCount: fileCount, index: (index + 1), downloadedFiles: downloadedFiles + [image], errorCount: 0)
}
}
// else, download the file
else {
// If image exists, append the data
if let _ = imageData, let data = data {
imageData?.append(data)
}
// initialize the image data
else {
imageData = data
}
}
}
}) // end of filedata fetch
} // end of else statement
}
// bounds checking
let available = files.count
let n = howMany > available ? available : howMany
// grab the N latest images taken by the drone
let filesToDownload : [DJIMediaFile] = Array ( files.suffix(n) )
// start the recursive function
downloadNextImage(files: filesToDownload, fileCount: filesToDownload.count)
}
这是如何称呼它的：
// get current product
guard let drone = DJISDKManager.product() else {
Logger.logError("Product is connected but DJISDKManager.product is nil when attempting to download media")
return
}
// Get camera on drone
guard let camera: DJICamera = drone.camera else {
Logger.logError("Unable to detect Camera in initDownload()")
return
}
Logger.logH1("Successfully detected the camera")
// check if we can download images with the product
if !camera.isMediaDownloadModeSupported() {
Logger.logError("Product does not support media download mode")
return
}
// switch camera mode to allow for media downloads
camera.setMode( .mediaDownload, withCompletion: {(error) in
if error != nil {
print("\(error!.localizedDescription)")
}
else {
// get the media manager from the drone to gain access to the files
let manager = camera.mediaManager!
manager.refreshFileList(completion: { (error) in
if error != nil {
print("State: \(manager.fileListState.rawValue)")
print("Error refreshing list: \(error!.localizedDescription)")
}
else {
Logger.logH1("Refreshed file list")
print("State: \(manager.fileListState.rawValue)")
// get list of files
guard let files = manager.fileListSnapshot() else {
Logger.logError("No files to download")
return
}
Logger.logH1("There are files to download.. Beginning Download")
self.downloadImages(files: files, howMany: waypoints, maxErrors: 4, completion: { images in
Logger.logH1("Finished downloading: \(images.count) image(s)")
// do something with the images here
})
}
}) // end of file-refresh block
}
})// end of camera setMode block