如何在故事板中使用NSURLConnection下载文件 [英] how download file with NSURLConnection in storyboard

问题描述

我是 NSURLConnection 中的菜鸟。我搜索过谷歌并找到了这个网站，但我对此并不了解。

I am a noob in NSURLConnection. I have searched Google and found this site but I dont understand about it.

我的朋友们请说明我从文件夹中的网址下载的代码。

My friends please explain the code that I have downloaded from url in Document folder.

这是我的代码：

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSURL *url =[NSURL URLWithString:@"http://cdn.arstechnica.net/wp-content/uploads/2012/09/iphone5-intro.jpg"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    NSURLConnection *con  = [[NSURLConnection alloc]initWithRequest:request delegate:self];
    [con start];}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    //I dont know what thing put here
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)theData
{
    //I dont know what thing put here
}


- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    //I dont know what thing put here
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    UIAlertView *errorView = [[UIAlertView alloc]initWithTitle:@"Error" message:@"The Connection has been LOST" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
    [errorView show];
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}

推荐答案

使用 NSURLConnection ，试试这个

// Create the request.
NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://cdn.cultofmac.com/wp-content/uploads/2013/03/colorware-iphone-5-xl.jpg"]
                        cachePolicy:NSURLRequestUseProtocolCachePolicy
                    timeoutInterval:60.0];
// create the connection with the request
// and start loading the data
NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
if (theConnection) {
    // Create the NSMutableData to hold the received data.
    // receivedData is an instance variable declared elsewhere.
    receivedData = [[NSMutableData data] retain];
} else {
    // Inform the user that the connection failed.
}

有关NSURLConnection的更多信息，请参阅： URL加载系统编程指南

For more info on NSURLConnection Refer this :URL Loading System Programming Guide

编辑

此处 recievedData 是类型的实例变量 NSMutableData

Here recievedData is the instance variable of type NSMutableData

-(void)downloadWithNsurlconnection
{

    NSURL *url = [NSURL URLWithString:currentURL];
    NSURLRequest *theRequest = [NSURLRequest requestWithURL:url         cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:60];
    receivedData = [[NSMutableData alloc] initWithLength:0];
    NSURLConnection * connection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self     startImmediately:YES];


}


- (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    [receivedData setLength:0];
}

- (void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    [receivedData appendData:data];


}

- (void) connectionDidFinishLoading:(NSURLConnection *)connection {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *pdfPath = [documentsDirectory stringByAppendingPathComponent:[currentURL stringByAppendingString:@".jpg"]];
    NSLog(@"Succeeded! Received %d bytes of data",[receivedData length]);
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
    [receivedData writeToFile:pdfPath atomically:YES];
}

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