导入AFNetworking 2.0 文件夹,引入头文件AFNetworking.h
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*使用NSURLSessionDownloadTask来下载一张图片,并带有下载进度(以下两段代码是一起的,注意)
NSProgress为iOS7新增加的类
// 定义一个progress指针
NSProgress *progress; // 创建一个URL链接
NSURL *url = [NSURL URLWithString:\
@"http://wallpapers.wallbase.cc/rozne/wallpaper-3020771.jpg"]; // 初始化一个请求
NSURLRequest *request = [NSURLRequest requestWithURL:url]; // 获取一个Session管理器
AFHTTPSessionManager *session = [AFHTTPSessionManager manager]; // 开始下载任务
NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithRequest:request progress:&progress destination:^NSURL *(NSURL *targetPath, NSURLResponse *response)
{
// 拼接一个文件夹路径
NSURL *documentsDirectoryURL = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil]; // 根据网址信息拼接成一个完整的文件存储路径并返回给block
return [documentsDirectoryURL URLByAppendingPathComponent:[response suggestedFilename]]; } completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error)
{
// 结束后移除掉这个progress
[progress removeObserver:self
forKeyPath:@"fractionCompleted"
context:NULL];
}]; // 设置这个progress的唯一标示符
[progress setUserInfoObject:@"someThing" forKey:@"Y.X."];
[downloadTask resume]; // 给这个progress添加监听任务
[progress addObserver:self
forKeyPath:@"fractionCompleted"
options:NSKeyValueObservingOptionNew
context:NULL];
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if ([keyPath isEqualToString:@"fractionCompleted"] && [object isKindOfClass:[NSProgress class]]) {
NSProgress *progress = (NSProgress *)object;
NSLog(@"Progress is %f", progress.fractionCompleted); // 打印这个唯一标示符
NSLog(@"%@", progress.userInfo);
}
}
*使用AFHTTPRequestOperation下载图片的操作,不过,没有进度显示(源码中也没有相关方法-_-!)
// 组织一个请求
NSURLRequest *request = \
[NSURLRequest requestWithURL:\
[NSURL URLWithString:@"https://images0.cnblogs.com/i/607542/201404/050759358125578.png"]]; // 建立请求操作
AFHTTPRequestOperation *requestOperation = \
[[AFHTTPRequestOperation alloc] initWithRequest:request]; // 进行操作的配置(下载图片,还有其他的类型)
requestOperation.responseSerializer = [AFImageResponseSerializer serializer]; // 设置获取数据的block
[requestOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject)
{
// 源码中为并发线程池返回了主线程
NSLog(@"Response: %@", responseObject); } failure:^(AFHTTPRequestOperation *operation, NSError *error)
{
// 源码中为并发线程池返回了主线程
NSLog(@"Image error: %@", error);
}]; // 开始执行
[requestOperation start];
*下载队列,且能在后台下载,关闭了应用后还继续下载(这个功能好^_^)
Upload and download tasks in background sessions are performed by an external daemon instead of by the app itself. As a result, the transfers continue in the background even if the app is suspended, exits, or crashes.
在后台进行上传或者下载任务的会话,是被系统的程序管理而不是应用本身来管理的.所以呢,当app挂了,推出了甚至崩溃了,这个下载还是继续着的
@interface DownloadsViewController ()
{
AFURLSessionManager *manager;
}
@end
// 配置后台下载会话配置
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration backgroundSessionConfiguration:@"downloads"]; // 初始化SessionManager管理器
manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration]; // 获取添加到该SessionManager管理器中的下载任务
NSArray *downloadTasks = [manager downloadTasks]; // 如果有下载任务
if (downloadTasks.count)
{
NSLog(@"downloadTasks: %@", downloadTasks); // 继续全部的下载链接
for (NSURLSessionDownloadTask *downloadTask in downloadTasks)
{
[downloadTask resume];
}
}
按按钮添加一个下载任务到manager中
- (void)addDownloadTask:(id)sender
{
// 组织URL
NSURL *URL = [NSURL URLWithString:@"http://pic.cnitblog.com/avatar/607542/20140226182241.png"]; // 组织请求
NSURLRequest *request = [NSURLRequest requestWithURL:URL]; // 给SessionManager管理器添加一个下载任务
NSURLSessionDownloadTask *downloadTask = \
[manager downloadTaskWithRequest:request
progress:nil
destination:^NSURL *(NSURL *targetPath, NSURLResponse *response) {
NSURL *documentsDirectoryPath = [NSURL fileURLWithPath:[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject]];
return [documentsDirectoryPath URLByAppendingPathComponent:[targetPath lastPathComponent]];
} completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) {
NSLog(@"File downloaded to: %@", filePath);
}];
[downloadTask resume]; // 打印下载的标示
NSLog(@"%d", downloadTask.taskIdentifier);
}