转载自：http://zhidao.baidu.com/link?url=jNTz6lkL1way8bJ-WPY197Pe9aEM_ql-MZbVJsM5tXr7Mv82W70QQ5a9UlvhMMS6xicm1HVprRAE3Cypr-zqdwDGDrS3BbbHEuW2-xgvlX_
方法一：一般将服务器第一次返回的数据保存在沙盒里面。这样在手机断网的情况下可以从本地读取数据了。
1.保存到沙盒的代码：
[plain] view
plaincopy
+ (void)saveCache:(int)type andID:(int)_id andString:(NSString *)str;
{
NSUserDefaults * setting = [NSUserDefaults standardUserDefaults];
NSString * key = [NSString stringWithFormat:@"detail-%d-%d",type, _id];
[setting setObject:str forKey:key];
[setting synchronize];
}
2.读取本地沙盒的代码
读取之前首先根据type和Id判断本地是否有
[plain] view
plaincopy
+ (NSString *)getCache:(int)type andID:(int)_id
{
NSUserDefaults * settings = [NSUserDefaults standardUserDefaults];
NSString *key = [NSString stringWithFormat:@"detail-%d-%d",type, _id];
NSString *value = [settings objectForKey:key];
return value;
}
如果沙盒里面有数据
[plain] view
plaincopy
NSString *value = [Tool getCache:5 andID:self.QiuTime];
if (value) {
NSDictionary *backdict = [value JSONValue];
if ([backdict objectForKey:@"items"]) {
NSArray *array=[NSArray arrayWithArray:[backdict objectForKey:@"items"]];
for (NSDictionary *qiushi in array) {
QiuShi *qs=[[[QiuShi alloc]initWithDictionary:qiushi] autorelease];
[self.list addObject:qs];
}
}
[self.tableView reloadData];
}
[self.tableView tableViewDidFinishedLoadingWithMessage:@"数据全部加载完了.."];
self.tableView.reachedTheEnd = YES;
方法二：使用ASIHTTPRequest和ASIDownloadCache实现本地缓存
1、设置全局的Cache
在AppDelegate.h中添加一个全局变量
[plain] view plaincopy
@interface AppDelegate : UIResponder
{
ASIDownloadCache *myCache;
}
@property (strong, nonatomic) UIWindow *window;
@property (nonatomic,retain) ASIDownloadCache *myCache;
在AppDelegate.m中的- (BOOL)application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions方法中添加如下代码
[plain] view plaincopy
//自定义缓存
ASIDownloadCache *cache = [[ASIDownloadCache alloc] init];
self.myCache = cache;
[cache release];
//设置缓存路径
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentDirectory = [paths objectAtIndex:0];
[self.myCache setStoragePath:[documentDirectory stringByAppendingPathComponent:@"resource"]];
[self.myCache setDefaultCachePolicy:ASIOnlyLoadIfNotCachedCachePolicy];
在AppDelegate.m中的dealloc方法中添加如下语句
[plain] view plaincopy
[myCache release];
到这里为止，就完成了全局变量的声明。
2、设置缓存策略
在实现ASIHTTPRequest请求的地方设置request的存储方式，代码如下
[plain] view plaincopy
NSString *str = @"http://....../getPictureNews.aspx";
NSURL *url = [NSURL URLWithString:str];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
//获取全局变量
AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
//设置缓存方式
[request setDownloadCache:appDelegate.myCache];
//设置缓存数据存储策略，这里采取的是如果无更新或无法联网就读取缓存数据
[request setCacheStoragePolicy:ASICachePermanentlyCacheStoragePolicy];
request.delegate = self;
[request startAsynchronous];
3、清理缓存数据
我在这里采用的是手动清理数据的方式，在适当的地方添加如下代码，我将清理缓存放在了应用的设置模块：
[plain] view plaincopy
AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
[appDelegate.myCache clearCachedResponsesForStoragePolicy:ASICachePermanentlyCacheStoragePolicy];
这里清理的是ASICachePermanentlyCacheStoragePolicy这种存储策略的缓存数据，如果更换其他的参数的话，即可清理对应存储策略的缓存数据。