ios - 用swift和objective-c下载文件
<p><p>我有 2 个项目，使用 2 种不同的语言。 <code>Objective-c</code> 项目和 <code>swift</code> 项目从 url 下载文件。 </p>
<p>问题在于 <code>objective-c</code> 中文件的下载速度比 <code>swift</code> 中更快。为什么会这样？如何解决？</p>
<p>我的快速代码:</p>
<pre><code>override func viewDidLoad() {
super.viewDidLoad()
let backgroundSessionConfiguration = URLSessionConfiguration.background(withIdentifier: "backgroundSession")
backgroundSession = Foundation.URLSession(configuration: backgroundSessionConfiguration, delegate: self, delegateQueue: OperationQueue.main)
}
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
if indexPath.row > 0 { print(indexPath.row)
let path = NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.documentDirectory, FileManager.SearchPathDomainMask.userDomainMask, true)
print(path)
let documentDirectoryPath:String = path
let fileManager = FileManager()
let destinationURLForFile = URL(fileURLWithPath: documentDirectoryPath.appendingFormat("/file\(indexPath.row).mp3"))
if fileManager.fileExists(atPath: destinationURLForFile.path){
self.performSegue(withIdentifier: "detailSegue", sender: self)
print(indexPath.row)
}else{
index = indexPath.row
let url = URL(string: "link\(indexPath.row).mp3")!
downloadTask = backgroundSession.downloadTask(with: url)
downloadTask.resume()
circularProgressView = FFCircularProgressView(frame: CGRect(x: CGFloat(0), y: CGFloat(0), width: CGFloat(24), height: CGFloat(24)))
tableView.cellForRow(at: indexPath)?.accessoryView = self.circularProgressView
self.view.addSubview(circularProgressView)
circularProgressView.startSpinProgressBackgroundLayer()
}
}
}
//MARK: URLSessionDownloadDelegate
func urlSession(_ session: URLSession,
downloadTask: URLSessionDownloadTask,
didFinishDownloadingTo location: URL){
let path = NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.documentDirectory, FileManager.SearchPathDomainMask.userDomainMask, true)
let documentDirectoryPath:String = path
let fileManager = FileManager()
let destinationURLForFile = URL(fileURLWithPath: documentDirectoryPath.appendingFormat("/file\(index).mp3"))
do {
try fileManager.moveItem(at: location, to: destinationURLForFile)
}catch{
print("An error occurred while moving file to destination url")
}
}
func urlSession(_ session: URLSession,
downloadTask: URLSessionDownloadTask,
didWriteData bytesWritten: Int64,
totalBytesWritten: Int64,
totalBytesExpectedToWrite: Int64){
progress1 = Int(Float(totalBytesWritten))
total1 = Int(Float(totalBytesExpectedToWrite))
let percentage = String(format: "%.f%%", ((self.progress1 / self.total1) * 100))
(print(String(format: percentage, "%.f%%")))
DispatchQueue.main.async(execute: {() -> Void in
self.circularProgressView.progress = (CGFloat(self.progress1) / CGFloat(self.total1))
self.circularProgressView.stopSpinProgressBackgroundLayer()
})
}
//MARK: URLSessionTaskDelegate
func urlSession(_ session: URLSession,
task: URLSessionTask,
didCompleteWithError error: Error?){
downloadTask = nil
if (error != nil) {
print(error!.localizedDescription)
}else{
print("The task finished transferring data successfully")
}
}
</code></pre>
<p>我的 Objective-C 代码:</p>
<pre><code>- (void)viewDidLoad
{
;
_session = delegate:self delegateQueue:];
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.row == 1) {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = ;
NSString *filePath = ;
BOOL fileExists = [ fileExistsAtPath:filePath isDirectory:false];
if (!fileExists) {
UIAlertController * alert = [UIAlertController
alertControllerWithTitle:@""
message:@""
preferredStyle:UIAlertControllerStyleActionSheet];
UIAlertAction* actionAdd = [UIAlertAction
actionWithTitle:@""
style:UIAlertActionStyleDefault
handler:^(UIAlertAction * action)
{
;
_url1 =;
_downloadTask1 = ;
;
self.circularPV1 = [ initWithFrame:CGRectMake(0, 0, 24, 24)];
.accessoryView = self.circularPV1;
;
;
}];
UIAlertAction* actionCancel = [UIAlertAction
actionWithTitle:@""
style:UIAlertActionStyleCancel
handler:^(UIAlertAction * action)
{
;
}];
;
;
alert.popoverPresentationController.sourceView = self.view;
alert.popoverPresentationController.sourceRect = CGRectMake(self.view.bounds.size.width / 3.4, self.view.bounds.size.height / 4.0, 1.0, 1.0);
;
}
if (fileExists) {
;
}
}
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location
{
if (downloadTask == _downloadTask1) {
_paths1 = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
_documentsDirectory1 = ;
NSFileManager *fileManager = ;
NSURL *newLocation = ];
NSError *error;
;
}
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWrittentotalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite;
{
if( downloadTask == _downloadTask1){
self.progress1 = (float) totalBytesWritten;
self.total1 =(float) totalBytesExpectedToWrite;
NSString *percentage = ;
(NSLog (percentage, @"%.f%%"));
dispatch_async(dispatch_get_main_queue(), ^{
;
;
});
}
}
</code></pre></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>您的 swift 代码正在使用后台 URLsession 。操作系统对这些下载的优先级较低。 </p>
<p>如果您不需要使用后台 session ，您可以在创建 session 时模仿 Objective C 代码:</p>
<pre><code>session = URLSession(configuration:URLSessionConfiguration.default delegate:self delegateQueue:OperationQueue.main)
</code></pre></p>
<p style="font-size: 20px;">关于ios - 用swift和objective-c下载文件，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/42886955/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/42886955/
</a>
</p>
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