数据库总结完之后，下面来总结下网络这块,写博客的目的是为了让想学习IOS的不用去培训机构就能学习。

////  ViewController.m//  UrlConnection////  Created by City--Online on 15/4/27.//  Copyright (c) 2015年 CYW. All rights reserved.//#define imageUrl @"http://assets.sbnation.com/assets/2512203/dogflops.gif"#import "ViewController.h"@interface ViewController ()
     
      {    UIImageView *imageView;    UIActivityIndicatorView *indicatorView;    UIProgressView *progessView;    UILabel *progressLabel;    NSMutableData *imgData;    long long allBytes;}@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    imgData=[NSMutableData data];    [self initUI];    [self startDownLoadImage];        }-(void)startDownLoadImage{    NSURL *url=[NSURL URLWithString:imageUrl];    NSURLRequest *request=[NSURLRequest requestWithURL:url];    //    block//    NSOperationQueue *queue=[NSOperationQueue mainQueue];//    [NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {//        if (data) {//            imageView.image=[UIImage imageWithData:data];//            [indicatorView stopAnimating];////        }//    }];//  代理    [NSURLConnection connectionWithRequest:request delegate:self];//    NSURLConnection *connection=[[NSURLConnection alloc]initWithRequest:request delegate:self startImmediately:YES];//    [connection start];}//连接失败-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{    NSLog(@"连接失败");}//获得响应-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{    imgData.length=0;    //获取文件大小    allBytes=[response expectedContentLength];        //获取文件名    NSString *filename=[response suggestedFilename];    NSLog(@"文件名:%@",filename);        //获取文件类型    NSString *contentType=[response MIMEType];    NSLog(@"文件类型:%@",contentType);        //状态码    NSHTTPURLResponse *httpResponse=(NSHTTPURLResponse*)response;    NSInteger statusCode=[httpResponse statusCode];    NSLog(@"状态码:%ld",statusCode);        //响应头信息    NSDictionary *allHeaderFields=[httpResponse allHeaderFields];    NSLog(@"%@",allHeaderFields);        }//接收到数据-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{    //追加数据    [imgData appendData:data];     //计算进度    CGFloat progress=(CGFloat)imgData.length/allBytes;    progessView.progress=progress;    progressLabel.text=[NSString stringWithFormat:@"%2f",progress];    NSLog(@"%f",progress); }//响应完成-(void)connectionDidFinishLoading:(NSURLConnection *)connection{    imageView.image=[UIImage imageWithData:imgData];    [indicatorView stopAnimating];}-(void)initUI{    imageView = [[UIImageView alloc] initWithFrame:CGRectMake(10, 40, 300, 300)];    //默认图片    imageView.image = [UIImage imageNamed:@"photo"];    [self.view addSubview:imageView];        indicatorView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];    indicatorView.frame = CGRectMake(0, 0, 60, 60);    indicatorView.center = CGPointMake(imageView.frame.size.width/2, imageView.frame.size.height/2);    //indicatorView.hidesWhenStopped = NO;    [indicatorView startAnimating];    [imageView addSubview:indicatorView];        //CGRectGetMaxY(imageView.frame) == imageView.frame.origin.y + imageView.frame.size.height    //CGRectGetMaxX(progessLabel.frame) == progessLabel.frame.origin.x + progessLabel.frame.size.width        //进度条    progessView = [[UIProgressView alloc] initWithProgressViewStyle:UIProgressViewStyleDefault];    progessView.frame = CGRectMake(imageView.frame.origin.x, CGRectGetMaxY(imageView.frame)+20, 200, 20);    [self.view addSubview:progessView];            progressLabel = [[UILabel alloc] initWithFrame:CGRectMake(CGRectGetMaxX(progessView.frame), progessView.frame.origin.y - 10, 80, 20)];    progressLabel.text = @"0.00";    progressLabel.textAlignment = NSTextAlignmentCenter;    [self.view addSubview:progressLabel];}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end