如何從Web上加載圖像，並在獲取某些數據後立即將其顯示在視圖中

Question

如何從Web上加載圖像，並在獲取一些數據和數據後立即將其放入UIImageViewController中可能無法完全下載。

換句話說，當我得到圖像的部分數據並在視圖中顯示圖像的一部分時。

Answer 1

在ASIHTTP Wrapper的幫助下，我早先完成了同樣的事情（多次請求下載）。

頭文件

#import <UIKit/UIKit.h> 
#import "ASIHTTPRequest.h" 
#import "ASINetworkQueue.h" 

@interface TestViewController : UIViewController { 
    ASINetworkQueue *networkQueue; 

    IBOutlet UIImageView *imageView1; 
    IBOutlet UIImageView *imageView2; 
    IBOutlet UIImageView *imageView3; 
    IBOutlet UIProgressView *progressIndicator; 
    IBOutlet UISwitch *accurateProgress; 
    IBOutlet UIProgressView *imageProgressIndicator1; 
    IBOutlet UIProgressView *imageProgressIndicator2; 
    IBOutlet UIProgressView *imageProgressIndicator3; 
    IBOutlet UILabel *imageLabel1; 
    IBOutlet UILabel *imageLabel2; 
    IBOutlet UILabel *imageLabel3; 
    IBOutlet UITextView *myTextView; 
    BOOL failed; 

} 

實現文件

- (IBAction)fetchThreeImages:(id)sender 
{ 
    [imageView1 setImage:nil]; 
    [imageView2 setImage:nil]; 
    [imageView3 setImage:nil]; 

    if (!networkQueue) { 
     networkQueue = [[ASINetworkQueue alloc] init]; 
    } 
    failed = NO; 
    [networkQueue reset]; 
    [networkQueue setDownloadProgressDelegate:progressIndicator]; 
    [networkQueue setRequestDidFinishSelector:@selector(imageFetchComplete:)]; 
    [networkQueue setRequestDidFailSelector:@selector(imageFetchFailed:)]; 
    [networkQueue setShowAccurateProgress:[accurateProgress isOn]]; 
    [networkQueue setDelegate:self]; 

    ASIHTTPRequest *request; 
    request = [ASIHTTPRequest requestWithURL:[NSURL URLWithString:@"http://allseeing-i.com/ASIHTTPRequest/tests/images/small-image.jpg"]]; 
    [request setDownloadDestinationPath:[[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:@"1.png"]]; 
    [request setDownloadProgressDelegate:imageProgressIndicator1]; 
    [request setUserInfo:[NSDictionary dictionaryWithObject:@"request1" forKey:@"name"]]; 
    [networkQueue addOperation:request]; 

    request = [[[ASIHTTPRequest alloc] initWithURL:[NSURL URLWithString:@"http://allseeing-i.com/ASIHTTPRequest/tests/images/medium-image.jpg"]] autorelease]; 
    [request setDownloadDestinationPath:[[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:@"2.png"]]; 
    [request setDownloadProgressDelegate:imageProgressIndicator2]; 
    [request setUserInfo:[NSDictionary dictionaryWithObject:@"request2" forKey:@"name"]]; 
    [networkQueue addOperation:request]; 

    request = [[[ASIHTTPRequest alloc] initWithURL:[NSURL URLWithString:@"http://allseeing-i.com/ASIHTTPRequest/tests/images/large-image.jpg"]] autorelease]; 
    [request setDownloadDestinationPath:[[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:@"3.png"]]; 
    [request setDownloadProgressDelegate:imageProgressIndicator3]; 
    [request setUserInfo:[NSDictionary dictionaryWithObject:@"request3" forKey:@"name"]]; 
    [networkQueue addOperation:request]; 

    [networkQueue go]; 
} 


- (void)imageFetchComplete:(ASIHTTPRequest *)request 
{ 
    UIImage *img = [UIImage imageWithContentsOfFile:[request downloadDestinationPath]]; 
    if (img) { 
     if ([imageView1 image]) { 
      if ([imageView2 image]) { 
       [imageView3 setImage:img]; 
      } else { 
       [imageView2 setImage:img]; 
      } 
     } else { 
      [imageView1 setImage:img]; 
     } 
    } 
} 

- (void)imageFetchFailed:(ASIHTTPRequest *)request 
{ 
    if (!failed) { 
     if ([[request error] domain] != NetworkRequestErrorDomain || [[request error] code] != ASIRequestCancelledErrorType) { 
      UIAlertView *alertView = [[[UIAlertView alloc] initWithTitle:@"Download failed" message:@"Failed to download images" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil] autorelease]; 
      [alertView show]; 
     } 
     failed = YES; 
    } 
} 

隨意問任何問題。