How to refresh images using HJCache? - iphone

Question

I'm trying to display an image from a webcam in my app using HJCache.
The webcam refreshes its image every 5 minutes.
I'd like to have a refresh button, so that users could click it to see a new image (if available).
My code so far:
-(void)viewDidLoad {
// init HJObjManager
objMan = [[HJObjManager alloc] initWithLoadingBufferSize:6 memCacheSize:20];
// refresh button
UIBarButtonItem *buttonRefresh = [[UIBarButtonItem alloc]
initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh
target:self
action:#selector(refreshPhoto:)];
self.navigationItem.rightBarButtonItem = buttonRefresh;
[buttonRefresh release];
NSURL *url = [NSURL URLWithString: #"http://webcamurl"];
img1.url = url;
[self.objMan manage:img1];
}
-(IBAction) refreshPhoto: (id) sender {
// ?
}
Could you give me an hint on how to implement refreshPhoto?
Edit: ender pointed me to emptyCache. If I understand it ok, it should be used by HJMOFileCache, so my code now is:
-(void)viewDidLoad {
NSString *documentsDirectory;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
documentsDirectory = [paths objectAtIndex:0];
documentsDirectory = [documentsDirectory stringByAppendingPathComponent:#"imageCache/"];
objMan = [[HJObjManager alloc] initWithLoadingBufferSize:6 memCacheSize:20];
HJMOFileCache* fileCache = [[[HJMOFileCache alloc] initWithRootPath:documentsDirectory] autorelease];
fileCache.fileCountLimit = 100;
fileCache.fileAgeLimit = 300; // 5 min
objMan.fileCache = fileCache;
// refresh button
UIBarButtonItem *buttonRefresh = [[UIBarButtonItem alloc]
initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh
target:self
action:#selector(refreshPhoto:)];
self.navigationItem.rightBarButtonItem = buttonRefresh;
[buttonRefresh release];
NSURL *url = [NSURL URLWithString: #"http://webcamurl"];
img1.url = url;
[self.objMan manage:img1];
[super viewDidLoad];
}
-(IBAction) refreshPhoto: (id) sender {
[self.objMan.fileCache emptyCache];
[self.objMan manage:img1];
}
It doesn't work though, when I click the refresh button nothing happens, the image does not refresh.
Any idea?
Edit: ender suggested that maybe the cache files do not get deleted by emptyCache (if I understand it right), but it looks like they actually do.
From NSLog before and after the emptyCache:
2011-09-09 16:57:33.842 Ready dir before emptyCache: (
"http:__www.meteogallipoli.it_cam_cam1.jpg"
)
2011-09-09 16:57:33.845 Loading dir before emptyCache: (
)
2011-09-09 16:57:33.856 Ready dir after emptyCache: (
)
2011-09-09 16:57:33.859 Loading dir after emptyCache: (
)
"Ready" and "Loading" are the directories where objMan stores files already downloaded and being downloaded, respectively.
Maybe the problem is in making objMan manage the image again?

Answer 1

I think its because you configured the object manager with both a file cache and a memory cache. When you empty the file cache, there are still images in the memory cache? Try instanciating the object manager with

Answer 2

if you only have an image, you can use [objMan emptyCache];
If you want to refresh only an image, you can save it in a different dir and use this method instead:
[objMan deleteAllFilesInDir:path];
Of course, you will have to make the query again:
[self.objMan manage:img1];