iOS網路編程-ASIHTTPRequest小例子-資料請求隊列

執行個體：請求隊列

我們通過一個例子介紹一下請求隊列使用，我們設計了一個應用，使用者點擊GO按鈕從伺服器同時下載兩張圖片顯示在畫面中。

 

我們直接看看主視圖控制器ViewController.h代碼如下：

#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 們需要引入ASI架構的兩個標頭檔ASIHTTPRequest.h和ASINetworkQueue.h。其中imageView1和 imageView2是與畫面對應的兩個圖片視圖控制項。還定義了ASINetworkQueue  類型的networkQueue屬性。我們直接看看主視圖控制器ViewController.m中點擊GO按鈕調用方法，代碼如下：

- (IBAction)onClick:(id)sender {if (!_networkQueue) {_networkQueue = [[ASINetworkQueue alloc] init];                       ①}// 停止以前的隊列[_networkQueue cancelAllOperations];                                      ②// 建立ASI隊列[_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使用者郵箱>”,i];NSURL *url = [NSURL URLWithString:[strURL URLEncodedString]];ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];request.tag = i;                                                  ⑥[_networkQueue addOperation:request];                                   ⑦}[_networkQueue go];                                                   ⑧}

 

我們再看看它們的回調方法，代碼：

- (void)requestFinished:(ASIHTTPRequest *)request{NSData *data = [request responseData];NSError *eror;NSDictionary *resDict = [NSJSONSerialization JSONObjectWithData:dataoptions: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:@”錯誤資訊”message:errorStrdelegate:nilcancelButtonTitle:@”OK”otherButtonTitles: nil];[alertView show];}if ([_networkQueue requestsCount] == 0) {                                    ②[self setNetworkQueue:nil];}NSLog(@”請求成功”);}- (void)requestFailed:(ASIHTTPRequest *)request                              ③{NSError *error = [request error];NSLog(@”%@”,[error localizedDescription]);if ([_networkQueue requestsCount] == 0) {[self setNetworkQueue:nil];}NSLog(@”請求失敗”);}- (void)queueFinished:(ASIHTTPRequest *)request                              ④{if ([_networkQueue requestsCount] == 0) {[self setNetworkQueue:nil];}NSLog(@”隊列完成”);}

 

 

requestFinished: 方法是請求對象成功回調方法，因此有兩個請求對象它會被調用兩次，在第①行代碼中我們根據GO按鈕點擊事件設定的 請求對象的tag屬性，來判斷是哪個請求對象的回調。進而載入到顯示不同的圖片視圖。第②代碼[_networkQueue requestsCount]可以判斷隊列中請求對象的個數。