Question

其他问题： 接收数据总长度现在为89973.但是使用下面的代码将其转换为字符串会返回一个（null）字符串。 解决了它：将编码更改为NSASCIIStringEncoding，现在可以正常工作。

NSString *responseString = [[NSString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding];
NSLog(@"Received string: %@", responseString);

解决了问题： 我正在尝试登录网站并获取返回的数据。一切都很好，重定向工作就像他们应该的那样。

还有多次调用didReceiveData，但奇怪的是：数据长度为零。即使我从didReceiveData内部NSLog数据长度。

以下是.m和.h文件以及生成的NSLog信息。

我是Objective-C的新手，我现在正试图解决这个问题几个小时，但我似乎无法找到原因。

我希望有人可以帮我看看。

这是.m文件

#import "SiteConnection.h"

@implementation SiteConnection

@synthesize username;
@synthesize password;

// Other
- (void) printInstanceVars {

}

- (void) getInformation {
    // Enable Network Indicator
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];

    // Set the request URL
    url = [NSURL URLWithString:@"http://url.com"];

    // Create the request using the URL defined above
    NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:url];

    // Change User-Agent to a Browser
    [request setValue:@"Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:13.0) Gecko/20100101 Firefox/13.0.1" forHTTPHeaderField:@"User-Agent"];

    // Change method to POST
    [request setHTTPMethod:@"POST"];

    // Create POST string
    NSString *requestData = [NSString stringWithFormat:@"data=value"];

    // Append POST string to the request
    [request setHTTPBody: [requestData dataUsingEncoding:NSUTF8StringEncoding]];

    // Initialize the connection
    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO];

    // Start the connection
    [connection start];
}

- (NSURLRequest *)connection:(NSURLConnection *)connection
         willSendRequest:(NSURLRequest *)request
        redirectResponse:(NSURLResponse *)response
{
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
    int statusCode = [httpResponse statusCode];

    // http statuscodes between 300 & 400 is a redirect ...
    if (response && statusCode >= 300 && statusCode < 400) {
        NSLog(@"Redirecting to : %@ (%u)", [request URL], statusCode);
    }

    return request;
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    [receivedData setLength:0];

    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
    NSLog(@"Response: %u (%@)", [httpResponse statusCode], [NSHTTPURLResponse localizedStringForStatusCode:[httpResponse statusCode]]);
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    [receivedData appendData:data];
    NSLog(@"Receiving data... Length: %d", [receivedData length]);
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    NSLog(@"Error: %@", [error localizedDescription]);
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    // Hide Network Indicator
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];

    // Display data length
    NSLog(@"Total received data: %d", [receivedData length]);

    // Convert data into string and display it
    NSString *responseString = [[NSString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding];
    NSLog(@"Received string: %@", responseString);
    //NSLog(@"Cookies: %@", [[NSHTTPCookieStorage sharedHTTPCookieStorage] description]);
}

这是.h文件

#import <Foundation/Foundation.h>

@class StatusViewController;

@interface SiteConnection : NSObject {
    NSString *username;
    NSString *password;
    NSURL *url;
    NSMutableData *receivedData;
}

@property NSString *username;
@property NSString *password;

// Other
- (void) printInstanceVars;
- (void) getInformation;

@end

这是由此产生的NSLog：

2012-07-02 15:41:12.578 Vodafone[25051:11303] Response: 200 (no error)
2012-07-02 15:41:12.578 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.580 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.580 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.582 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.583 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.585 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.586 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.587 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.590 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.590 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.591 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.592 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.596 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.601 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.605 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.608 Vodafone[25051:11303] Receiving data... Length: 0
2012-07-02 15:41:12.608 Vodafone[25051:11303] Total received data: 0
2012-07-02 15:41:12.608 Vodafone[25051:11303] Received string:

Answer 1

看起来你忘记了：

NSMutableData *receivedData = [[NSMutableData alloc] init];

Answer 2

我认为你永远不会初始化receivedData。所以你把你收到的数据附加到一个nil指针，显然没有效果;-) 在使用之前尝试receivedData = [[NSMutableData alloc] init];之类的东西。

Answer 3

这样做：

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    if (!receivedData)
    {
        receivedData = [NSMutableData data];
    }

    [receivedData appendData:data];

    NSLog(@"Receiving data... Length: %d", [receivedData length]);
}

NSURLConnection确实触发didReceiveData，但返回的数据为零

3 个答案: