iOS 同步异步下载

 

#import "ViewController.h"

 

@interface ViewController ()<NSURLConnectionDataDelegate,NSURLConnectionDelegate>

{

    NSMutableData * myImageData;

    int num;

}

@end

 

@implementation ViewController

 

- (void)viewDidLoad {

    [super viewDidLoad];

    num =1;

 

    NSInteger a =0;

    CGFloat startPointX = (self.view.frame.size.width-20)/5;

    CGFloat startPointY = (self.view.frame.size.width-20)/5;

    for (int i=0; i<5; i++) {

        for (int j=0; j<6; j++) {

            UIImageView * image=[[UIImageView alloc]initWithFrame:CGRectMake(i*(startPointX+4)+2, j*startPointY, startPointX, startPointY)];

            image.image=[UIImage imageNamed:@"1"];

            image.tag=++a;

            [self.view addSubview:image];

            

        }

    }

    for (NSInteger i=a; i>=0; i--) {

//        UIImageView * imageview=(UIImageView*)[self.view viewWithTag:i+1];

        

//        imageview.image=[self notSameTime];

        

    }

    [self notSameTime];

    [self blocksameTime];

    // Do any additional setup after loading the view, typically from a nib.

}

#pragma mark 同步下载

-(UIImage*)SameTime

{

    NSString * str =@"http://a.hiphotos.baidu.com/exp/whcrop=90,80/sign=69220e04f703738dde1f5a60dc6b8d68/b21c8701a18b87d6f75cdabb060828381f30fd7c.jpg";

    NSURL * url =[NSURL URLWithString:str];

    NSURLRequest * request =[NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10.0f];

    //    其中缓存协议是个枚举类型包含：

    //    NSURLRequestUseProtocolCachePolicy（基础策略）

    //    NSURLRequestReloadIgnoringLocalCacheData（忽略本地缓存）

    //    NSURLRequestReturnCacheDataElseLoad（首先使用缓存，如果没有本地缓存，才从原地址下载）

    //    NSURLRequestReturnCacheDataDontLoad（使用本地缓存，从不下载，如果本地没有缓存，则请求失败，此策略多用于离线操作）

    //    NSURLRequestReloadIgnoringLocalAndRemoteCacheData（无视任何缓存策略，无论是本地的还是远程的，总是从原地址重新下载）

    //    NSURLRequestReloadRevalidatingCacheData（如果本地缓存是有效的则不下载，其他任何情况都从原地址重新下载）

    

    NSURLResponse * response=nil;

    NSError *error;

    NSData * imageData=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

    UIImage * image=[UIImage imageWithData:imageData];

    return image;

}

#pragma mark block异步下载

-(void)blocksameTime

{

     NSString * str =@"http://a.hiphotos.baidu.com/exp/whcrop=90,80/sign=69220e04f703738dde1f5a60dc6b8d68/b21c8701a18b87d6f75cdabb060828381f30fd7c.jpg";

    NSURL * url=[NSURL URLWithString:str];

    NSURLRequest * request=[NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:10.0f];

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

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

        UIImageView* image =(UIImageView*)[self.view viewWithTag:5];

        image.image=[UIImage imageWithData:data];

    }];

    

 

}

 

#pragma mark 异步下载

-(UIImage *)notSameTime

{

    NSString * str =@"http://a.hiphotos.baidu.com/exp/whcrop=90,80/sign=69220e04f703738dde1f5a60dc6b8d68/b21c8701a18b87d6f75cdabb060828381f30fd7c.jpg";

    NSURL * url =[NSURL URLWithString:str];

    NSURLRequest * request =[NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10.0f ];

    

 

   [NSURLConnection connectionWithRequest:request delegate:self];

        UIImage * image;

    return image;

}

//下载结束

-(void)connectionDidFinishLoading:(NSURLConnection *)connection

{

    UIImageView * imageview=(UIImageView*)[self.view viewWithTag:num];

    num++;

    

    imageview.image=[UIImage imageWithData:myImageData];

    myImageData=nil;

}

//下载错误

 

-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error

{

    NSLog(@"发生错误＝%@",error);

    

}

//加载到的数据

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data

{

    [myImageData appendData:data];

}

请求过程中如果url包含中文

get请求中

    NSString * urlstring=@"http://c.hiphotos.baidu.com/image/pic/item/泽锋";

    urlstring=[urlstring stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

post 请求中需要对请求体转码

    request.HTTPBody=[@"zefeng=则分" dataUsingEncoding:NSUTF8StringEncoding];

 

 

 

 

 

 

 

 

 

 

//开始加载数据

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response

{

    myImageData=[NSMutableData data];

    

}