iOS缓存-内存缓存

为了减少与服务器的连接沟通次数，提高应用程序的执行速度，使用了iOS的缓存机制

#import "YoungViewController.h"

@interface YoungViewController ()<NSURLConnectionDelegate>

{

NSURLConnection * connection;

}

@end

@implementation YoungViewController

- (void)viewDidLoad

{

[super viewDidLoad];

UIButton * btnCache = [UIButton buttonWithType:UIButtonTypeRoundedRect];

btnCache.frame = CGRectMake(50, 50, 100, 30);

[btnCache setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];

[btnCache setBackgroundColor:[UIColor orangeColor]];

[btnCache setTitle:@"缓存" forState:UIControlStateNormal];

[btnCache addTarget:self action:@selector(Chcal:)forControlEvents:UIControlEventTouchUpInside];

[self.view insertSubview:btnCache atIndex:0];

}

-(void)Chcal:(id)sender

{

NSString *paramURLAsString = @"http://www.baidu.com/";

if([paramURLAsString length]==0)

{

NSLog(@"nil or empty is given!");

return;

}

NSURLCache * urlCache = [NSURLCache sharedURLCache];

/*设置缓存空间的大小--1M*/

[urlCache setMemoryCapacity:1*1024*1024];

/*创建一个nsurl*/

NSURL *url = [NSURL URLWithString:paramURLAsString];

/*创建一个请求*/

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:urlcachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0f];

/*从请求中获取缓存输出*/

NSCachedURLResponse *respose = [urlCache cachedResponseForRequest:request];

//判断是否有缓存

if(respose!=nil)

{

NSLog(@"如果有缓存输出,从缓存中获取数据");

//[request setCachePolicy:NSURLRequestReloadIgnoringCacheData];//忽略缓存，重新下载

//[request setCachePolicy:NSURLRequestReturnCacheDataElseLoad];//缓存中不存在才下载

//[request setCachePolicy:NSURLRequestReturnCacheDataDontLoad];//使用缓存，绝对不请求网络

//[request setCachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData];//忽略缓存，重新下载

//[request setCachePolicy:NSURLRequestReloadRevalidatingCacheData];//缓存于请求是否相同，同不下载，不同下载。

}

connection = nil;

NSURLConnection *newConnection = [[NSURLConnection alloc]initWithRequest:request delegate:selfstartImmediately:YES];

connection = newConnection;

}

- (NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)redirectResponse

{

NSLog(@"即将发送请求.....");

return(request);

}

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

{

NSLog(@"将接收输出.....");

}

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

{

NSLog(@"数据长度为 = %lu", (unsigned long)[data length]);

}

- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse

{

//如果之前缓存中已经存在数据程序是不走这里的

NSLog(@"将缓存输出.....");

return(cachedResponse);

}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection

{

NSLog(@"请求完成.....");

}

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

{

NSLog(@"请求失败");

}