iPhone开发下载网络数据的几种方法总结

1
使用NSURLConnection的同步方法下载

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source

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01.

NSString
*urlAsString = @

"http://www.jouhu.com/json/info.zip"

;－－－要下载的全路径名

02.

NSURL
*url = [NSURL URLWithString:urlAsString];

03.

NSURLRequest
*request = [NSURLRequest requestWithURL:url];

04.

NSError
*error = nil;

05.

06.

NSData
*data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:&error];

07.

/*下载的数据*/

08.

if

(data!=nil)
{

09.

NSLog(@

"下载成功"

);

10.

if

([data
writeToFile:@

"/Users/sunningning/Desktop/activation.zip"

atomically:YES])
{－－下载到目的路径名

11.

NSLog(@

"保存成功！"

);

12.

}

13.

else

14.

{

15.

NSLog(@

"保存失败！"

);

16.

}

17.

}

18.

else

{

19.

NSLog(@

"%@"

,error);

20.

}

2 使用NSURLConnection的异步方法下载

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01.

NSString
*urlAsString = @

"http://www.apple.com"

;

02.

NSURL
*url = [NSURL URLWithString:urlAsString];

03.

NSURLRequest
*urlRequest = [NSURLRequest requestWithURL:url];

04.

NSOperationQueue
*queue = [[NSOperationQueue alloc] init];

05.

06.

[NSURLConnection
sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response,NSData *data, NSError *error)

07.

{

08.

if

([data
length] >

0

&&
error == nil){

09.

NSString
*html = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

10.

NSLog(@

"HTML
= %@"

,
html); }

11.

12.

else

if

([data
length] ==

0

&&
error == nil){

13.

NSLog(@

"Nothing
was downloaded."

);

14.

}

15.

16.

else

if

(error
!= nil){

17.

NSLog(@

"Error
happened = %@"

,
error); }

18.

}];

3 使用NSURLConnection的异步+GCD的方法下载

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01.

+
(

void

)performRequestWithUri:(NSString
*)requestUri params:(NSDictionary *)params completionHandler:(

void

(^)(NSDictionary
*, NSError *))completionBlock

02.

{

03.

04.

//
Generate the URL

05.

NSString
*requestUrl = [NSString stringWithFormat:@

"http://the.api.com%@"

,
requestUri];

06.

07.

//
Create the connection

08.

NSURLRequest
*request = [[NSURLRequest alloc] initWithURL:[NSURL URLWithString:requestUrl]];

09.

10.

//
Make an NSOperationQueue

11.

NSOperationQueue
*queue = [[NSOperationQueue alloc] init];

12.

[queue
setName:@

"com.your.unique.queue.name"

];

13.

14.

//
Send an asyncronous request on the queue

15.

[NSURLConnection
sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {

16.

17.

//
If there was an error getting the data

18.

if

(error)
{

19.

20.

dispatch_async(dispatch_get_main_queue(),
^(

void

)
{

21.

completionBlock(nil,
error);

22.

});

23.

return

;

24.

}

25.

26.

//
Decode the data

27.

NSError
*jsonError;

28.

NSDictionary
*responseDict = [NSJSONSerialization JSONObjectWithData:data options:

0

error:&jsonError];

29.

30.

//
If there was an error decoding the JSON

31.

if

(jsonError)
{

32.

33.

dispatch_async(dispatch_get_main_queue(),
^(

void

)
{

34.

35.

});

36.

return

;

37.

}

38.

39.

//
All looks fine, lets call the completion block with the response data

40.

dispatch_async(dispatch_get_main_queue(),
^(

void

)
{

41.

completionBlock(responseDict,
nil);

42.

});

43.

}];

44.

}

具体调用方法：

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source

print?

1.

[SHAPIController
performRequestWithUri:@

"http://www.jouhu.com/json/info.php"

params:nil
completionHandler:^(NSDictionary *response, NSError *error) {

2.

3.

if

(error)
{

4.

NSLog(@

"%@"

,
error);

5.

}

6.

7.

NSLog(@

"%@"

,
response);

8.

}];

返回的数据根据我们而定.

4 实现delegate的方法实现异步

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01.

NSURLConnection
*conn= [[NSURLConnection alloc]

02.

initWithRequest:theRequest
delegate:self];

03.

[conn
start];

04.

if

(conn)

05.

{

06.

NSLog(@

"Connection
Successful"

);

07.

}

08.

else

09.

{

10.

NSLog(@

"Connection
could not be made"

);

11.

}

12.

}

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source

print?

01.

-
(

void

)connection:(NSURLConnection
*)connection didReceiveResponse:(NSURLResponse *)theResponse {

02.

self.response
= theResponse;

03.

[data
setLength:

0

];

//
reset data

04.

}

05.

06.

-
(

void

)connection:(NSURLConnection
*)connection didReceiveData:(NSData *)theData {

07.

[data
appendData:theData];

//
append incoming data

08.

}

09.

10.

-
(

void

)connection:(NSURLConnection
*)connection didFailWithError:(NSError *)error {

11.

[UIApplication
sharedApplication].networkActivityIndicatorVisible = NO;

12.

self.data
= nil;

13.

if

(handler)
{ [queue addOperationWithBlock:^{ handler(response, nil, error); }];}

14.

}

15.

16.

-
(

void

)connectionDidFinishLoading:(NSURLConnection
*)connection {

17.

[UIApplication
sharedApplication].networkActivityIndicatorVisible = NO;

18.

//
TODO: Are we passing the arguments to the block correctly? Should we copy them?

19.

handleData(self.data);

//处理数据，需要定义方法

20.

}

我们自身的应用采用的是最后一种方法，对于很多图片更新的，可以采取第三种方法，第一种方法是同步数据下载，容易造成UI阻塞。需要注意。