iOS网络编程-ASIHTTPRequest小例子-数据请求队列

我们通过一个例子介绍一下请求队列使用，我们设计了一个应用，用户点击GO按钮从服务器同时下载两张图片显示在画面中。

 

我们直接看看主视图控制器ViewController.h代码如下：

#import “ASIHTTPRequest.h”

#import “ASINetworkQueue.h”

#import “NSNumber+Message.h”

#import “NSString+URLEncoding.h”

 

@interface ViewController : UIViewController

 

@property (weak, nonatomic) IBOutlet UIImageView *imageView1;

@property (weak, nonatomic) IBOutlet UIImageView *imageView2;

@property (strong) ASINetworkQueue  *networkQueue;

 

- (IBAction)onClick:(id)sender;

@end

我们需要引入ASI框架的两个头文件ASIHTTPRequest.h和ASINetworkQueue.h。其中imageView1和 imageView2是与画面对应的两个图片视图控件。还定义了ASINetworkQueue  类型的networkQueue属性。我们直接看看主视图控制器ViewController.m中点击GO按钮调用方法，代码如下：

- (IBAction)onClick:(id)sender {

if (!_networkQueue) {

_networkQueue = [[ASINetworkQueue alloc] init];                       ①

}

// 停止以前的队列

[_networkQueue cancelAllOperations];                                      ②

// 创建ASI队列

[_networkQueue setDelegate:self];

[_networkQueue setRequestDidFinishSelector:@selector(requestFinished:)];      ③

[_networkQueue setRequestDidFailSelector:@selector(requestFailed:)];          ④

[_networkQueue setQueueDidFinishSelector:@selector(queueFinished:)];          ⑤

 

for (int i=1; i<3; i++) {

NSString *strURL = [[NSString alloc] initWithFormat:

@”http://iosbook3/download.php?email=%@&FileName=test%i.jpg”,

@”<你的iosbook1.com用户邮箱>”,i];

NSURL *url = [NSURL URLWithString:[strURL URLEncodedString]];

ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];

request.tag = i;                                                  ⑥

[_networkQueue addOperation:request];                                   ⑦

}

[_networkQueue go];                                                   ⑧

}

我们再看看它们的回调方法，代码：

- (void)requestFinished:(ASIHTTPRequest *)request

{

NSData *data = [request responseData];

NSError *eror;

NSDictionary *resDict = [NSJSONSerialization JSONObjectWithData:data

options:NSJSONReadingAllowFragments error:&eror];

if (!resDict) {

UIImage *img = [UIImage imageWithData:data];

if (request.tag ==1) {                                                ①

_imageView1.image = img;

} else {

_imageView2.image = img;

}

} else {

NSNumber *resultCodeObj = [resDict objectForKey:@"ResultCode"];

NSString *errorStr = [resultCodeObj errorMessage];

UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@”错误信息”

message:errorStr

delegate:nil

cancelButtonTitle:@”OK”

otherButtonTitles: nil];

[alertView show];

}

if ([_networkQueue requestsCount] == 0) {                                    ②

[self setNetworkQueue:nil];

}

NSLog(@”请求成功”);

}

- (void)requestFailed:(ASIHTTPRequest *)request                              ③

{

NSError *error = [request error];

NSLog(@”%@”,[error localizedDescription]);

if ([_networkQueue requestsCount] == 0) {

[self setNetworkQueue:nil];

}

NSLog(@”请求失败”);

}

- (void)queueFinished:(ASIHTTPRequest *)request                              ④

{

if ([_networkQueue requestsCount] == 0) {

[self setNetworkQueue:nil];

}

NSLog(@”队列完成”);

}

requestFinished:方法是请求对象成功回调方法，因此有两个请求对象它会被调用两次，在第①行代码中我们根据GO按钮点击事件设定的 请求对象的tag属性，来判断是哪个请求对象的回调。进而加载到显示不同的图片视图。第②代码[_networkQueue requestsCount]可以判断队列中请求对象的个数。

出自www.iosbook3.com