UI 网络请求（同步GET，同步POST，异步GET，异步POST）具体操作

#import "MainViewController.h"  
  
@interface MainViewController ()<NSURLConnectionDataDelegate>  
  
@property (nonatomic, retain)UIImageView *imageView;  
  
@property (nonatomic, retain)NSMutableData *data;// 可变数据 Data 用于拼接每次接受来的数据块  
@end  
  
@implementation MainViewController  
  
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil  
{  
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];  
    if (self) {  
        // Custom initialization  
    }  
    return self;  
}  
  
- (void)viewDidLoad  
{  
    [super viewDidLoad];  
    // Do any additional setup after loading the view.  
    self.imageView = [[UIImageView alloc] initWithFrame:CGRectMake(20, 20, 280, 280)];  
    self.imageView.backgroundColor = [UIColor redColor];  
    [self.view addSubview:self.imageView];  
    [self.imageView release];  
      
    UIButton *button1 = [UIButton buttonWithType:UIButtonTypeSystem];  
    button1.frame = CGRectMake(20, 320, 120, 40);  
    button1.backgroundColor = [UIColor brownColor];  
    [button1 setTitle:@"同步 GET" forState:UIControlStateNormal];  
    [button1 addTarget:self action:@selector(buttonClicked1:) forControlEvents:UIControlEventTouchUpInside];  
    [self.view addSubview:button1];  
      
      
    UIButton *button2 = [UIButton buttonWithType:UIButtonTypeSystem];  
    button2.frame = CGRectMake(180, 320, 120, 40);  
    button2.backgroundColor = [UIColor brownColor];  
    [button2 setTitle:@"同步 POST" forState:UIControlStateNormal];  
    [button2 addTarget:self action:@selector(buttonClicked2:) forControlEvents:UIControlEventTouchUpInside];  
    [self.view addSubview:button2];  
      
      
    UIButton *button3 = [UIButton buttonWithType:UIButtonTypeSystem];  
    button3.frame = CGRectMake(20, 400, 120, 40);  
    button3.backgroundColor = [UIColor brownColor];  
    [button3 setTitle:@"异步 GET" forState:UIControlStateNormal];  
    [button3 addTarget:self action:@selector(buttonClicked3:) forControlEvents:UIControlEventTouchUpInside];  
    [self.view addSubview:button3];  
      
      
    UIButton *button4 = [UIButton buttonWithType:UIButtonTypeSystem];  
    button4.frame = CGRectMake(180, 400, 120, 40);  
    button4.backgroundColor = [UIColor brownColor];  
    [button4 setTitle:@"异步 POST" forState:UIControlStateNormal];  
    [button4 addTarget:self action:@selector(buttonClicked4:) forControlEvents:UIControlEventTouchUpInside];  
    [self.view addSubview:button4];  
      
}  
  
- (void)buttonClicked1:(UIButton *)button  
{  
    // 同步GET  
    // 1.拼接网络地址  
    NSString *str  = @"http://cdn.gq.com.tw.s3-ap-northeast-1.amazonaws.com/userfiles/images_A1/6954/2011100658141857.jpg"  
    ;  
    // 2.将地址转化为URL对象  
    NSURL *url = [NSURL URLWithString:str];  
      
    // 3. 创建一个请求（request）  
    // 参数1： 请求地址（NSURL）  
    // 参数2：给请求选择一个缓存策略  
    // 参数3: 请求超时时间  
    NSMutableURLRequest *requset = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:30.0];  
    // 4. 给请求设置 请求方式  
    [requset setHTTPMethod:@"GET"];  
    // 5. 将请求发送给服务器  
      
    // 同步连接  
    // 参数1：请求（request）  
    // 参数2：响应信息  
    // 参数3：错误信息  
    // 同步连接的方法 会一直等待 数据完整接受之后才继续执行  
    NSURLResponse *response = nil;  
    NSError *error = nil;  
    NSData *data = [NSURLConnection sendSynchronousRequest:requset returningResponse:&response error:&error];  
      
    //在这里获得的是完整的 data数据  
    NSLog(@"服务器响应信息：%@", response);  
      
    // 使用NSData数据  
    UIImage *image = [UIImage imageWithData:data];  
    self.imageView.image = image;  
    NSLog(@"%@", NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES));  
  
}  
-(void)dealloc  
{  
    [_data release];  
    [_imageView release];  
    [super dealloc];  
}  
- (void)buttonClicked2:(UIButton *)button  
{  
    // 同步POST  
    NSString *str = @"http://ipad-bjwb.bjd.com.cn/DigitalPublication/publish/Handler/APINewsList.ashx";  
    NSURL *url = [NSURL URLWithString:str];  
      
    // 创建请求  
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];  
    // 设置请求方式  
    [request setHTTPMethod:@"POST"];  
      
    // 产生一个body  
    NSString *bodyStr = @"date=20131129&startRecord=1&len=30&udid=1234567890&terminalType=Iphone&cid=213";  
    NSData *data = [bodyStr dataUsingEncoding:NSUTF8StringEncoding];  
      
    // 设置post请求 附带的数据  
    [request setHTTPBody:data];  
      
    // 同步连接 获取内容  
    NSURLResponse *response = nil;  
    NSData *dataBack = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];  
    NSLog(@"%@", response);  
      
    // 测试返回数据内容  
    NSString *result = [[NSString alloc] initWithData:dataBack encoding:NSUTF8StringEncoding];  
    NSLog(@"%@", result);  
  
}  
  
- (void)buttonClicked3:(UIButton *)button  
{  
    // 异步  
    // 1. 产生请求  
    NSString *str = @"http://pic13.nipic.com/20110313/2686941_211532129160_2.jpg";  
    NSURL *url = [NSURL URLWithString:str];  
      
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];  
      
    [request setHTTPMethod:@"GET"];  
      
    // 2.建立连接  
    // 异步联接 不会卡死界面  
    // 参数1:设定好的请求  
    // 参数2：设定网络请求的代理人  
    [NSURLConnection connectionWithRequest:request delegate:self];  
      
      
}  
// 当收到服务器的响应信息 的时候 调用  
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response  
{  
    // 当每次需要接受新的数据的时候 初始化data属性  
    NSLog(@"%s", __FUNCTION__);  
    self.data = [NSMutableData data];  
}  
// 当收到服务器发送来的 data数据块 的时候 调用  
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data  
{  
    NSLog(@"%s", __FUNCTION__);  
    [self.data appendData:data];  
}  
// 当数据接受完毕 的时候 调用  
-(void)connectionDidFinishLoading:(NSURLConnection *)connection  
{  
    // 调用这个方法 说明 self.data属性已经是一个完整的数据  
    NSLog(@"%s", __FUNCTION__);  
    UIImage *image = [UIImage imageWithData:self.data];  
    self.imageView.image = image;  
}  
- (void)buttonClicked4:(UIButton *)button  
{  
    // 异步POST  
  
    NSString *str = @"http://ipad-bjwb.bjd.com.cn/DigitalPublication/publish/Handler/APINewsList.ashx";  
    NSURL *url = [NSURL URLWithString:str];  
      
    // 创建请求  
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];  
    // 设置请求方式  
    [request setHTTPMethod:@"POST"];  
      
    // 设置body  
    NSString *bodyStr = @"date=20131129&startRecord=1&len=30&udid=1234567890&terminalType=Iphone&cid=213";  
    NSData *data = [bodyStr dataUsingEncoding:NSUTF8StringEncoding];  
      
    // 设置post请求 附带的数据  
    [request setHTTPBody:data];  
      
      
      
    // 2. 连接  
    // block 基础上的异步连接  
      
      
    // 参数1：请求  
    // 参数2：返回主线程  
    // 参数3：  
    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {  
        // 当异步联接完毕 而且 请求但完整的数据（参数data）之后 才执行这个块的内容  
          
        // 在这个块中 写处理数据的代码 （解析/转化为image/音频/视频）  
        NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];  
        NSLog(@"%@", dic);  
    }];  
      
}