Threading loading images from a device to a tableView in swift - ios

Question

I can't find anything online about threading loading an image from a device and scrolling smoothly through a tableview. There is one on ray wen about this, but it doesn't really help me for my situation.
Does anybody have any advice or code which would help to allow a tableview to scroll smoothly and load images from the device's temporary directory?

Answer 1

i did exactly as mentioned at tutorial, but with modification for nsoperation subclass
this is methods for fetch
-(void) updateData
{
[self.pendingOperations.downloadQueue addOperationWithBlock:^{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSArray *filePathes = [self recursiveRecordsForResourcesOfType:#[#"png", #"jpeg", #"jpg",#"pdf"] inDirectory:documentsDirectory];
#synchronized (self) {
self.documents = filePathes;
NSLog(#"documents count %#", #([self.documents count]));
}
dispatch_async(dispatch_get_main_queue(), ^(void){
//Run UI Updates
[self.delegate modelDidUpdate:self];
});
}];
}
- (NSArray *)recursiveRecordsForResourcesOfType:(NSArray *)types inDirectory:(NSString *)directoryPath{
NSMutableArray *filePaths = [[NSMutableArray alloc] init];
NSMutableDictionary *typesDic = [NSMutableDictionary dictionary];
for (NSString *type in types)
[typesDic setObject:type forKey:type];
// Enumerators are recursive
NSDirectoryEnumerator *enumerator = [[NSFileManager defaultManager] enumeratorAtPath:directoryPath];
NSString *filePath;
while ((filePath = [enumerator nextObject]) != nil){
// If we have the right type of file, add it to the list
// Make sure to prepend the directory path
if([typesDic objectForKey:[filePath pathExtension]]){
//[filePaths addObject:[directoryPath stringByAppendingPathComponent:filePath]];
CURFileRecord *record = [CURFileRecord new];
record.filePath =[directoryPath stringByAppendingPathComponent:filePath];
record.fileName = filePath;
[filePaths addObject:record];
}
}
return filePaths;
}
this is .m for subclass
- (void)main {
// 4
#autoreleasepool {
if (self.isCancelled)
return;
NSData *fileData = [[NSFileManager defaultManager] contentsAtPath:self.fileRecord.filePath];
// self.fileRecord.fileData = fileData;
if (self.isCancelled) {
fileData = nil;
return;
}
if (fileData) {
UIImage *newImage;
if ([[self.fileRecord.filePath pathExtension] isEqualToString:#"pdf"])
{
CGPDFDocumentRef doc = [CURDocumentViewerUtilities MyGetPDFDocumentRef:fileData];
newImage = [CURDocumentViewerUtilities buildThumbnailImage:doc withSize:CGSizeMake(64, 96)];
}
else
{
newImage = [CURDocumentViewerUtilities makePreviewImageFromData:fileData];
}
self.fileRecord.previewImage = newImage;
}
else {
self.fileRecord.failed = YES;
}
fileData = nil;
if (self.isCancelled)
return;
// 5
[(NSObject *)self.delegate performSelectorOnMainThread:#selector(imageDownloaderDidFinish:) withObject:self waitUntilDone:NO];
}
}
With update func i've fetched pathes to proccess, and nsoperation subclass loads images. Works fine with 2000 images in fullhd - smoothly and without any lugs