1、 使用队列NSOperation下载时会将操作放在异步线程里面，不会放在主线程中
换一种方法进行下载：
- (void)download {
self.data = [NSMutableData data];
//发送请求
NSURL *url = [NSURL URLWithString:@"http://192.168.1.106:8080/MJServer/lufy.png"];
NSURLRequest *reuqest = [NSURLRequest requestWithURL:url];
[[NSURLConnection connectionWithRequest:reuqest delegate:self] start];
}
获取的数据需要进行拼接：（NSURLConnectionDataDelegate）
代理方法
1、- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
[self.data appendData:data]; // 拼接下载的数据
}
2、- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
UIImage *image = [UIImage imageWithData:self.data];
NSLog(@"下载完毕");
self.imageView.image = image;
}
大文件下载
1、下载方法：
- (void)download {
self.data = [NSMutableData data]; // 初始化data
NSURL *url = [NSURL URLWithString:@"http://192.168.1.106:8080/MJServer/movie.avi"];
// 发送请求
NSURLRequest *reuqest = [NSURLRequest requestWithURL:url];
// 使用NSURLConnection创建
[[NSURLConnection connectionWithRequest:reuqest delegate:self] start];
}
下载时使用的代理方法：
#pragma mark - 代理方法
// 开始接收数据时调用
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
[self.data appendData:data]; // 拼接数据
// 设置下载进度
self.progressView.progress = (float)self.data.length / (float)_totalLength;
}
#pragma mark 服务器有相应就会调用这个方法
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
NSHTTPURLResponse *rep = (NSHTTPURLResponse *)response;
_totalLength = [[[rep allHeaderFields] objectForKey:@"Content-Length"] intValue];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
//大文本数据存储在Caches中，不会被清除掉
NSString *cacheDir = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
NSString *dir = [cacheDir stringByAppendingPathComponent:@"movie"];
NSFileManager *mgr = [NSFileManager defaultManager];
// 是否为文件夹
BOOL isDir;
// 是否存在
BOOL exist = [mgr fileExistsAtPath:dir isDirectory:&isDir];
if (!exist) {
// 创建一个新的文件夹
[mgr createDirectoryAtPath:dir withIntermediateDirectories:YES attributes:nil error:nil];
}
NSString *path = [dir stringByAppendingPathComponent:@"mj.avi"];
// 将文件数据写入Library/Caches文件夹下
[self.data writeToFile:path atomically:YES];
}
原文：http://www.cnblogs.com/angongIT/p/3832716.html