我正在尝试在位于表格视图单元格中的 UIImage 中异步加载图像。有时它会在显示正确的图像之前显示来自另一个单元格的图像一秒钟。
这是我正在使用的代码
[[TMCache sharedCache] objectForKey:post[@"gif"] block:^(TMCache *cache, NSString *key, id object) {
if (object) {
if ([self isRowZeroVisible:indexPath.section]) {
[GIFLoader loadGIFData:object to:postGif for:feedTableView];
}
return;
}
dispatch_async(dispatch_get_main_queue(), ^{
__block NSURL* url = [NSURL URLWithString:post[@"gif"]];
NSURLRequest* req = [NSURLRequest requestWithURL:url];
OHURLLoader* loader = [OHURLLoader URLLoaderWithRequest:req];
[loader startRequestWithResponseHandler:nil
progress:nil
completion:^(NSData* receivedData, NSInteger httpStatusCode) {
if ([self isRowZeroVisible:indexPath.section]) {
[GIFLoader loadGIFData:receivedData to:postGif for:feedTableView];
}
[[TMCache sharedCache] setObject:receivedData forKey:post[@"gif"]];
} errorHandler:nil];
});
}];
[GIFLoader loadGIFData:receivedData to:postGif for:feedTableView]; is a method I created that loads GIFs in a uiimageview. it does that in a background thread and then assigns the Image in the main thread though.
对于异步加载，我需要遵循某些做法吗？
我不确定我的代码有什么问题。任何帮助将不胜感激
编辑
//Loading stuff into tableView
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
@autoreleasepool {
//Type of Cells
static NSString *simpleTableImageIdentifier = @"gifCell";
static NSString *simpleTableBodyIdentifier = @"bodyCell";
static NSString *simpleTableActionsIdentifier = @"actionsCell";
UITableViewCell *cell = nil;
//Data that goes in the cell
NSDictionary *post = [dataArray objectAtIndex:indexPath.section];
//User info
UIImageView *userAvatar;
UILabel *postUserFullNameLabel;
UILabel *postUsername;
//GIF Date
OHAttributedLabel* gifDate = nil;
NSMutableAttributedString* gifDateString;
//Feed GIF
NSString *gifBody = [[NSString alloc]init];
OHAttributedLabel* attrLabel = nil;
NSMutableAttributedString* mas;
//Location
OHAttributedLabel* gifLocation = nil;
NSMutableAttributedString* gifLocationString;
UILabel *locationBg;
//Buttons
UIButton *btn1 =[[UIButton alloc] initWithFrame:CGRectMake(11,0,50,30)];
UIButton *btn2 =[[UIButton alloc] initWithFrame:CGRectMake(69,0,50,30)];
UIButton *btn3 =[[UIButton alloc] initWithFrame:CGRectMake(259,0,50,30)];
if (indexPath.row == 0) {
cell = [tableView dequeueReusableCellWithIdentifier:simpleTableImageIdentifier];
if (cell == nil){
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableImageIdentifier];
}
__block UIImageView *postGif= (UIImageView *)[cell viewWithTag:104];
postGif.image = nil;
[[TMCache sharedCache] objectForKey:post[@"gif"] block:^(TMCache *cache, NSString *key, id object) {
if (object) {
if ([self isRowZeroVisible:indexPath.section]) {
[GIFLoader loadGIFData:object to:postGif for:feedTableView];
}
return;
}
dispatch_async(dispatch_get_main_queue(), ^{
__block NSURL* url = [NSURL URLWithString:post[@"gif"]];
NSURLRequest* req = [NSURLRequest requestWithURL:url];
OHURLLoader* loader = [OHURLLoader URLLoaderWithRequest:req];
[loader startRequestWithResponseHandler:nil
progress:nil
completion:^(NSData* receivedData, NSInteger httpStatusCode) {
if ([self isRowZeroVisible:indexPath.section]) {
[GIFLoader loadGIFData:receivedData to:postGif for:feedTableView];
}
[[TMCache sharedCache] setObject:receivedData forKey:post[@"gif"]];
} errorHandler:nil];
});
}];
postGif.layer.cornerRadius = 2.0;
postGif.layer.masksToBounds = YES;
postGif.clipsToBounds = YES;
locationBg = (UILabel *)[cell viewWithTag:106];
userAvatar = (UIImageView *)[cell viewWithTag:100];
if ([post [@"user_avatar"] length ] > 0) {
NSString *img = [@"https://d1f7i732a4e7fw.cloudfront.net/" stringByAppendingString:post [@"user_avatar"]];
[userAvatar setImageWithURL:[NSURL URLWithString:img] placeholderImage:[UIImage imageNamed:@"userDefaultPicture.png"]];
}else{
userAvatar.image = [UIImage imageNamed:@"userDefaultPicture.png"];
}
userAvatar.layer.cornerRadius = 18.0;
userAvatar.layer.borderWidth = 1.0;
userAvatar.layer.borderColor = (__bridge CGColorRef)([UIColor lightGrayColor]);
userAvatar.clipsToBounds = YES;
postUserFullNameLabel = (UILabel *)[cell viewWithTag:101];
postUserFullNameLabel.text = post[@"user_fullname"];
postUsername = (UILabel *)[cell viewWithTag:102];
postUsername.text = [NSString stringWithFormat:@"@%@",post[@"user_username"]];
gifDate = [[OHAttributedLabel alloc] initWithFrame:CGRectMake(246,9,60,21)];
gifDate.autoresizingMask = UIViewAutoresizingNone;
gifDate.centerVertically = YES;
gifDate.highlightedTextColor = [UIColor whiteColor];
gifDate.tag = 103;
gifDate.backgroundColor = [UIColor clearColor];
gifDate.extendBottomToFit = NO;
gifDateString = [NSMutableAttributedString attributedStringWithString:[NSString stringWithFormat:@"\ue003 %@",post[@"date"]]];
[gifDateString setFont:[UIFont fontWithName:@"Helvetica Neue" size:12.0]];
[gifDateString setFont:[UIFont fontWithName:@"icomoon" size:10.0] range:NSMakeRange(0,1)];
[gifDateString setTextColor:[UIColor whiteColor]];
[gifDateString setTextAlignment:kCTTextAlignmentRight lineBreakMode:kCTLineBreakByTruncatingTail];
[OHASBasicMarkupParser processMarkupInAttributedString:gifDateString];
gifDate.attributedText = gifDateString;
if (!(post[@"latitude"] == (id)[NSNull null])){
//Location of the Post
gifLocation = [[OHAttributedLabel alloc] initWithFrame:CGRectMake(165,27,141,21)];
gifLocation.autoresizingMask = UIViewAutoresizingNone;
gifLocation.centerVertically = YES;
gifLocation.highlightedTextColor = [UIColor whiteColor];
gifLocation.tag = 107;
gifLocation.backgroundColor = [UIColor clearColor];
gifLocation.extendBottomToFit = NO;
gifLocationString = [NSMutableAttributedString attributedStringWithString:[NSString stringWithFormat:@"\uf041 %@",post[@"locationName"]]];
[gifLocationString setFont:[UIFont fontWithName:@"Helvetica Neue" size:12.0]];
[gifLocationString setFont:[UIFont fontWithName:@"icomoon" size:12.0] range:NSMakeRange(0,1)];
[gifLocationString setTextColor:[UIColor whiteColor]];
[gifLocationString setTextAlignment:kCTTextAlignmentRight lineBreakMode:kCTLineBreakByTruncatingTail];
[OHASBasicMarkupParser processMarkupInAttributedString:gifLocationString];
gifLocation.attributedText = gifLocationString;
}
}
else if (indexPath.row == 1) {
cell = [tableView dequeueReusableCellWithIdentifier:simpleTableBodyIdentifier];
if (cell == nil){
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableBodyIdentifier];
}
//Body of GIF
// Add more from here http://www.easyapns.com/iphone-emoji-alerts
gifBody = post[@"body"];
attrLabel = [[OHAttributedLabel alloc] initWithFrame:CGRectMake(10,5,kLabelWidth,tableView.rowHeight-2*kLabelVMargin)];
attrLabel.autoresizingMask = UIViewAutoresizingFlexibleHeight;
attrLabel.centerVertically = NO;
attrLabel.automaticallyAddLinksForType = NSTextCheckingAllTypes;
attrLabel.delegate = self;
attrLabel.highlightedTextColor = UIColorFromRGB(0x333333);
attrLabel.tag = kAttributedLabelTag;
attrLabel.backgroundColor = [UIColor clearColor];
attrLabel.extendBottomToFit = YES;
[cell.contentView addSubview:attrLabel];
attrLabel = (OHAttributedLabel*)[cell viewWithTag:kAttributedLabelTag];
mas = [NSMutableAttributedString attributedStringWithString:gifBody];
[mas setFont:[UIFont fontWithName:@"Helvetica Neue" size:14.0]];
[mas setTextColor:UIColorFromRGB(0x333333)];
[mas setTextAlignment:kCTTextAlignmentLeft lineBreakMode:kCTLineBreakByWordWrapping];
[OHASBasicMarkupParser processMarkupInAttributedString:mas];
attrLabel.attributedText = mas;
}
else if (indexPath.row == 2) {
cell = [tableView dequeueReusableCellWithIdentifier:simpleTableActionsIdentifier];
if (cell == nil){
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableActionsIdentifier];
}
[self customizeButtons:btn1];
btn1.tag = (indexPath.section +1)*200;
btn1.titleLabel.font = [UIFont fontWithName:@"icomoon" size:16.0];
if ([post[@"is_Favoring"] boolValue]) {
[btn1 setTitleColor:UIColorFromRGB(0xE4717A) forState:UIControlStateNormal];
}else{
[btn1 setTitleColor:[UIColor lightGrayColor] forState:UIControlStateNormal];
}
[btn1 setTitle:@"\uf004" forState:UIControlStateNormal];
btn1.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
[btn1 addTarget:self
action:@selector(favorAction:)
forControlEvents:UIControlEventTouchUpInside];
[cell.contentView addSubview:btn1];
[self customizeButtons:btn2];
btn2.tag = (indexPath.section +1)*2000;
btn2.titleLabel.font = [UIFont fontWithName:@"icomoon" size:16.0];
[btn2 setTitleColor:[UIColor lightGrayColor] forState:UIControlStateNormal];
[btn2 setTitle:@"\ue000" forState:UIControlStateNormal];
[cell.contentView addSubview:btn2];
btn2.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
[btn2 addTarget:self
action:@selector(commentAction:)
forControlEvents:UIControlEventTouchUpInside];
[self customizeButtons:btn3];
btn3.titleLabel.font = [UIFont fontWithName:@"icomoon" size:16.0];
[btn3 setTitleColor:[UIColor lightGrayColor] forState:UIControlStateNormal];
[btn3 setTitle:@"\ue001" forState:UIControlStateNormal];
btn3.tag = (indexPath.section +1)*20000;
[cell.contentView addSubview:btn3];
btn3.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
[btn3 addTarget:self
action:@selector(otherAction:)
forControlEvents:UIControlEventTouchUpInside];
}
//Paginiation
if (indexPath.section == [dataArray count]-4 && indexPath.row == 1) {
[self loadNextPage];
}
return cell;
}
}