URLConnection下载图片

ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
<NSURLConnectionDataDelegate>
{
    UIImageView* imageView;
    NSMutableData* imageData;
}

@end

ViewController.m

#import "ViewController.h"

@implementation ViewController

#pragma mark - viewDidLoad Event
-(void)initImageViewFData
{
    imageData = [[NSMutableData alloc] init];
    imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 240)];
    [self.view addSubview:imageView];
    [imageView release];
}
-(void)startDownloadFImage
{
    NSString* str = @"http://192.168.88.8/sns/my/headimage.php?uid=865";
    NSURL* url = [NSURL URLWithString:str];
    
    //建立一个请求，设置url，缓存，超时时间
    NSURLRequest* request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:60.0];
    //发送同步请求
    //NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
    //异步请求
    [NSURLConnection connectionWithRequest:request delegate:self];
    //开始下载图片,什么时候知道下载完数据了
}

27 #pragma mark - viewDidLoad
- (void)viewDidLoad
{
    [super viewDidLoad];
    //初始.h里的字段
    [self initImageViewFData];
    //开始下载图片
    [self startDownloadFImage];
}


#pragma mark - NSURLConnectionDataDelegate
//下载完响应头，准备下载内容
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
    [imageData setLength:0];
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
}
//下载数据 , 多次调用
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
    //追加数据
    [imageData appendData:data];
}
//调用这个方法，证明下载完成
- (void)connectionDidFinishLoading:(NSURLConnection *)connection{
    UIImage* image = [UIImage imageWithData:imageData];
    imageView.image = image;
     [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}
//下载失败
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
    NSLog(@"下载失败");
}