iOS 下载

 #import "ViewController.h"

 @interface ViewController ()
 @property (strong, nonatomic) NSMutableData *data;
 @end

 @implementation ViewController

 - (void)viewDidLoad
 {
     [super viewDidLoad];
     // Do any additional setup after loading the view, typically from a nib.
     NSString *url = @"";
     url = [url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
     NSURL *newUrl = [NSURL URLWithString:url];

     NSURLRequest*request=[[NSURLRequest alloc]initWithURL:newUrl cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:100.0];//设置缓存和超时

     NSURLConnection*connection=nil;

     connection=[[NSURLConnection alloc]initWithRequest:request delegate:self startImmediately:YES];
 }

 -(void)connection:(NSURLConnection*)connection didReceiveResponse:(NSURLResponse*)response

 {//该方法在响应connection时调用

     NSLog(@"response");

     self.data=[[NSMutableData alloc]init];

     NSHTTPURLResponse*httpResponse=(NSHTTPURLResponse*)response;

     if(httpResponse&&[httpResponse respondsToSelector:@selector(allHeaderFields)]){

         NSDictionary*httpResponseHeaderFields=[httpResponse allHeaderFields];

         //mFileSize=[[httpResponseHeaderFields objectForKey:@"Content-Length"]longLongValue];

     }//获取文件文件的大小

 }

 -(void)connection:(NSURLConnection*)connection didFailWithError:(NSError*)error

 {//出错时调用

     NSLog(@"error");
 }

 -(void)connection:(NSURLConnection*)connection didReceiveData:(NSData*)data

 {//接受数据，在接受完成之前，该方法重复调用

     NSLog(@"receive");

     [self.data appendData:data];
 //
 //    _displayLabel.text=[NSString stringWithFormat:(@"%6.1fkb/%6.1fkb"),[_datalength]/1024.0,mFileSize/1024.0];
 //
 //    [_progressViewsetProgress:[_datalength]/(float)mFileSize];

 }

 -(void)connectionDidFinishLoading:(NSURLConnection*)connection

 {//完成时调用

     NSLog(@"Finish");

     NSString*filePath=[[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES)objectAtIndex:]stringByAppendingPathComponent:@"android.mp3"];

     [_data writeToFile:filePath atomically:NO];//将数据写入Documents目录。

     NSLog(@"%@",filePath);

 }