我在这个问题上坚持了最近2天。请帮帮我。
我的要求是，如果我在第二视图控制器中在后台下载文件并且在下载开始后我弹出到第一视图控制器并且如果我再次推送到第二视图控制器则应该继续该进度。
发生了什么：
NSMutableURLRequest，NSURLConnection开始下载。 我的日志也显示完美但UI未显示。我尝试了所有的答案。一切都是同样的问题。
这是我的全部代码：
在App Delegate方法中：
@property (copy) void (^backgroundSessionCompletionHandler)();
- (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier completionHandler:(void (^)())completionHandler
{
self.backgroundSessionCompletionHandler = completionHandler;
}
- (IBAction)downloadBackground:(id)sender;
- (IBAction)downloadImage:(id)sender;
@property (strong, nonatomic) IBOutlet UIImageView *downloadedImage;
@property (strong, nonatomic) IBOutlet UIProgressView *progressView;
@end
#import "CTViewController.h"
#import "CTSessionOperation.h"
#import "CTAppDelegate.h"
static NSString *downloadUrl = @"http://www.nasa.gov/sites/default/files/ladee_9.4.13_nasa_edge_0.jpg";
@interface CTViewController ()
@property (nonatomic, strong) NSOperation *downloadOperation;
@end
@implementation CTViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.progressView.progress = 0;
self.downloadedImage.hidden = NO;
self.progressView.hidden = YES;
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)downloadBackground:(id)sender {
// [self downloadImageInBackground:YES];
[self.navigationController popViewControllerAnimated:YES];
}
- (IBAction)downloadImage:(id)sender {
[self downloadImageInBackground:NO];
}
- (void)downloadImageInBackground:(BOOL)background{
if (self.downloadOperation){
return;
}
CTSessionOperation *operation = [CTSessionOperation new];
operation.downloadUrl = downloadUrl;
operation.progressAction = ^(double bytesWritten, double bytesExpected){
double progress = bytesWritten / bytesExpected;
dispatch_async(dispatch_get_main_queue(), ^{
self.progressView.progress = (float) progress;
});
};
operation.completionAction = ^(NSURL *imageUrl, BOOL success){
dispatch_async(dispatch_get_main_queue(), ^{
if (success){
UIImage *image = [UIImage imageWithContentsOfFile:[imageUrl path]];
self.downloadedImage.image = image;
NSLog(@"Done.......");
}
self.downloadedImage.hidden = NO;
self.progressView.progress = 0;
self.progressView.hidden = YES;
self.downloadOperation = nil;
});
};
operation.isBackground = background;
[operation enqueueOperation];
self.downloadedImage.hidden = YES;
self.progressView.hidden = NO;
self.downloadOperation = operation;
}
@end
#import <Foundation/Foundation.h>
typedef void (^CTProgressBlock)(double totalBytesWritten, double bytesExpected);
typedef void (^CTCompletionBlock)(NSURL *imageUrl, BOOL success);
@interface CTSessionOperation : NSOperation<NSURLSessionDelegate, NSURLSessionTaskDelegate, NSURLSessionDownloadDelegate>
@property (nonatomic) NSURLSessionDownloadTask *downloadTask;
@property (nonatomic) NSURLSession *session;
@property (nonatomic, strong) NSString *downloadUrl;
@property (strong) CTProgressBlock progressAction;
@property (strong) CTCompletionBlock completionAction;
@property (nonatomic, assign) BOOL isBackground;
- (void)enqueueOperation;
@end
#import "CTSessionOperation.h"
#import "CTAppDelegate.h"
@implementation CTSessionOperation
- (NSOperationQueue *)operationQueue{
static NSOperationQueue *operationQueue = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
operationQueue = [NSOperationQueue new];
[operationQueue setMaxConcurrentOperationCount:NSOperationQueueDefaultMaxConcurrentOperationCount];
});
return operationQueue;
}
- (NSURLSession *)session {
static NSURLSession *session = nil;
static NSURLSession *backgroundSession = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
NSURLSessionConfiguration *backgroundConfiguration = [NSURLSessionConfiguration
backgroundSessionConfiguration:@"com.captech.NSURLSample.BackgroundSession"];
backgroundSession = [NSURLSession sessionWithConfiguration:backgroundConfiguration
delegate:self
delegateQueue:nil];
});
return self.isBackground ? backgroundSession : session;
}
- (void)enqueueOperation{
[[self operationQueue] addOperation:self];
}
#pragma mark - NSOperation
- (void)start {
if (!self.isCancelled){
NSURL *downloadURL = [NSURL URLWithString:self.downloadUrl];
NSURLRequest *request = [NSURLRequest requestWithURL:downloadURL];
self.downloadTask = [self.session downloadTaskWithRequest:request];
[self.downloadTask resume];
}
}
#pragma mark - NSURLSessionDownloadDelegate
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location {
NSFileManager *fileManager = [NSFileManager defaultManager];
NSArray *urls = [fileManager URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask];
NSURL *documentsDirectory = [urls objectAtIndex:0];
NSURL *originalUrl = [[downloadTask originalRequest] URL];
NSURL *destinationUrl = [documentsDirectory URLByAppendingPathComponent:[originalUrl lastPathComponent]];
NSError *error;
[fileManager removeItemAtURL:destinationUrl error:NULL];
BOOL success = [fileManager copyItemAtURL:location toURL:destinationUrl error:&error];
if (self.completionAction){
self.completionAction(destinationUrl, success);
}
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
if (downloadTask == self.downloadTask && self.progressAction){
self.progressAction((double)totalBytesWritten, (double)totalBytesExpectedToWrite);
}
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes {
}
#pragma mark - NSURLSessionTaskDelegate
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
if (self.progressAction){
self.progressAction((double)task.countOfBytesReceived, (double)task.countOfBytesExpectedToReceive);
}
self.downloadTask = nil;
}
#pragma mark - NSURLSessionDelegate
- (void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session {
CTAppDelegate *appDelegate = (CTAppDelegate *)[[UIApplication sharedApplication] delegate];
if (appDelegate.backgroundSessionCompletionHandler) {
void (^completionHandler)() = appDelegate.backgroundSessionCompletionHandler;
appDelegate.backgroundSessionCompletionHandler = nil;
completionHandler();
}
}
@end
这是我的完整代码。请检查......：）
答案 0 :(得分：2)
我会处理下载与你的工作方式略有不同：）
以下是我将如何处理它：）
1.Declare NSOperation类并移动代码以将文件下载到此类
2.在您的NSOpertaion类中声明一个协议，该协议将当前下载状态通知给确认此协议的人
3.在你的第二个VC启动NSOpertaion并选择代表:)并相应地更新你的进度
以下是相同的一些代码：）
downloadAssets.h
#import <Foundation/Foundation.h>
@protocol AssetDownloadStatusProtocol <NSObject>
-(void)updateStatusWithValue:(float) progress;
@end
@interface downloadAssets : NSOperation
@property (nonatomic,weak) id<AssetDownloadStatusProtocol> delegate;
@property (nonatomic,strong) NSString *urlToDownload;
-(id)initWithURL:(NSString *)url;
@end
downloadAssets.m
@implementation downloadChatAssets
-(id)initWithURL:(NSString *)url{
self=[super init];
self.urlToDownload = url;
appdelegate=(AppDelegate *)[[UIApplication sharedApplication] delegate];
return self;
}
- (void)main {
// a lengthy operation
@autoreleasepool {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
if (self.isCancelled) {
appdelegate.downloadingOperation = nil;
return;
}
else{
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
AFURLSessionManager *manager = ... //start downloading
NSURLSessionDataTask *dataTask = [manager dataTaskWithRequest:URLRequest uploadProgress:nil downloadProgress:^(NSProgress * _Nonnull downloadProgress) {
if (self.isCancelled) {
appdelegate.downloadingOperation = nil;
return;
}
self.progressAmount = downloadProgress.fractionCompleted;
dispatch_async(dispatch_get_main_queue(), ^{
[self.delegate updateStatusWithValue:self.progressAmount];
});
} completionHandler:^(NSURLResponse * _Nonnull response, id _Nullable responseObject, NSError * _Nullable error) {
//handle completion here
}];
[dataTask resume];
}
});
}
}
@end
AppDelegate.h
@property (nonatomic, Strong) NSOperation *downloadingOperation;
SecondVC.h
@interface SecondVC : UIViewController <AssetDownloadStatusProtocol>
SecondVC.m
-(void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:YES];
if(appdelegate.downloadingOperation) {
appdelegate.downloadingOperation.delegate = self;
}
}
-(void)viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:YES];
if(appdelegate.downloadingOperation) {
appdelegate.downloadingOperation.delegate = nil;
}
}
-(void)updateStatusWithValue:(float)progress{
dispatch_async(dispatch_get_main_queue(), ^{
//update your progress here
[self.progressView updateProgressBarWithProgressValue:progress];
});
}
多数民众赞成:)
随时开始下载操作:)
appdelegate.downloadingOperation = yourDownloaderOperation;
[yourDownloaderOperation start];
你想阻止它说
[yourDownloaderOperation stop];
有更多的下载操作？考虑使用NSOperationQueue或Array在appdelegate中保存NSOperations：）
修改
根据您在评论中的要求，您可以在appDelegate中保留对CTOperation的引用。
@property (nonatomic, Strong) CTOperation *downloadingOperation;
您不需要声明协议，因为您已经声明了完成块和progressActionBlock：）
您只需要检查SecondVC viewWillAppear。
-(void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:YES];
if(appdelegate.downloadingOperation) {
appdelegate.downloadingOperation.progressAction = ^(double bytesWritten, double bytesExpected){
double progress = bytesWritten / bytesExpected;
dispatch_async(dispatch_get_main_queue(), ^{
self.progressView.progress = (float) progress;
});
};
appdelegate.downloadingOperation.completionAction = ^(NSURL *imageUrl, BOOL success){
dispatch_async(dispatch_get_main_queue(), ^{
if (success){
UIImage *image = [UIImage imageWithContentsOfFile:[imageUrl path]];
self.downloadedImage.image = image;
NSLog(@"Done.......");
}
self.downloadedImage.hidden = NO;
self.progressView.progress = 0;
self.progressView.hidden = YES;
self.downloadOperation = nil;
});
};
}
}
-(void)viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:YES];
if(appdelegate.downloadingOperation) {
appdelegate.downloadingOperation.progressAction = nil;
appdelegate.downloadingOperation.completionAction = nil;
}
}
并在你的downloadImageInBackground方法而不是self.downloadOperation = operation;中说'appdelegate.downloadingOperation = operation;
免责声明
请注意，本答案中提供的代码仅用于解释概念。我可能有语法或符号错误。请不要盲目地复制粘贴。
简单吧???有疑惑，ping我:)快乐编码：）