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我在xcode中有一個tableview，當前從parse.com後端下載並顯示到表中。它會下載一個小圖像並將圖像渲染成一個圓形以及每行的樣式。目前它下載大約5行並輸出可愛，但只要我上下滾動幾次tableview和應用程序變得緩慢。TableView在滾動上下幾次後變慢了
做一些研究，我可以看到建議，以添加數據提取另一個線程。目前，我對這一切都很陌生，我想知道是否有人可以幫助向我展示它是如何完成的。
我的cellForRowAtIndexPath看起來是這樣的：
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
tableView.separatorColor = [UIColor colorWithRed:192.0/255.0 green:196.0/255.0 blue:202.0/255.0 alpha:1];
if ([self.tableView respondsToSelector:@selector(setSeparatorInset:)]) {
[self.tableView setSeparatorInset:UIEdgeInsetsZero];
}
if (cell == nil)
{
cell = [[UITableViewCell alloc]
initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:CellIdentifier];
}
PFObject *games = [self.games objectAtIndex:indexPath.row];
//PFFile *imageFile = [games objectForKey:@"gameCover"];
NSString *gameName = [games objectForKey:@"name"];
NSArray *gamePlatforms = [games objectForKey:@"platform"];
NSString *platformsResult = [gamePlatforms componentsJoinedByString:@""];
NSDate *rDate = [games objectForKey:@"release_date"];
// Check to see if the date is set to a Quarter instead
if (rDate == (id)[NSNull null]) {
self.releaseDate = @"Q1/2014";
} else {
// Date on the right added to a subview
//Setup date
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
//uncomment to get the time only
//[formatter setDateFormat:@"hh:mm a"];
[formatter setDateFormat:@"dd"];
//[formatter setDateStyle:NSDateFormatterLongStyle];
//get the date today
NSDate *start = [NSDate date];
NSDateFormatter *f = [[NSDateFormatter alloc] init];
[f setDateFormat:@"YYYY-MM-dd"];
NSCalendar *gregorianCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [gregorianCalendar components:NSDayCalendarUnit
fromDate:start
toDate:rDate
options:0];
//NSLog(@"%ld", (long)[components day]);
NSInteger value = [components day];
NSString *myString = [NSString stringWithFormat:@"%0.0f days", (float)value];
if ([myString isEqual: @"1 days"])
{
myString = @"1 day";
}
self.releaseDate = myString;
}
// Cell Style
// Background Color
UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(10, 15, 300.0, 100.0)];
imageView.userInteractionEnabled = NO;
imageView.backgroundColor = [UIColor colorWithRed:209.0/255.0 green:230.0/255.0 blue:244.0/255.0 alpha:1];
// Icon Image
//Game Title Label
UILabel *titleLabel = [[UILabel alloc]initWithFrame:CGRectMake(80, 25, 200, 20)];
titleLabel.text = gameName;
titleLabel.backgroundColor = [UIColor clearColor];
titleLabel.font = [UIFont fontWithName:@"ProximaNova-Light" size:13];
titleLabel.textColor = [UIColor colorWithRed:44.0/255.0 green:127.0/255.0 blue:178.0/255.0 alpha:1];
// Game Date Label
UILabel *dateLabel = [[UILabel alloc]initWithFrame:CGRectMake(250, 80, 50, 20)];
dateLabel.text = self.releaseDate;
dateLabel.backgroundColor = [UIColor clearColor];
dateLabel.font = [UIFont fontWithName:@"ProximaNova-Light" size:13];
dateLabel.textColor = [UIColor colorWithRed:44.0/255.0 green:127.0/255.0 blue:178.0/255.0 alpha:1];
dateLabel.textAlignment = NSTextAlignmentRight;
// Game Platforms
UILabel *platformLabel = [[UILabel alloc]initWithFrame:CGRectMake(250, 25, 50, 20)];
platformLabel.text = platformsResult;
platformLabel.backgroundColor = [UIColor clearColor];
platformLabel.font = [UIFont fontWithName:@"ProximaNova-Light" size:13];
platformLabel.textColor = [UIColor colorWithRed:44.0/255.0 green:127.0/255.0 blue:178.0/255.0 alpha:1];
platformLabel.textAlignment = NSTextAlignmentRight;
// add the styles to the subview
[cell addSubview:imageView];
//[cell addSubview:iconView];
[cell addSubview:titleLabel];
[cell addSubview:dateLabel];
[cell addSubview:platformLabel];
PFFile *imageFile = [games objectForKey:@"gameCover"];
// If no image
if (imageFile != NULL) {
NSURL *imageFileUrl = [[NSURL alloc] initWithString:imageFile.url];
NSData *imageData = [NSData dataWithContentsOfURL:imageFileUrl];
UIImage *myImage = [UIImage imageWithData:imageData];
UIImageView *iconView = [[UIImageView alloc] initWithImage:myImage];
iconView.frame = CGRectMake(20.0, 25.0, 50.0, 50.0);
iconView.layer.masksToBounds = YES;
iconView.layer.cornerRadius = 25.0f;
[cell addSubview:iconView];
} else {
UIImageView *iconView = [[UIImageView alloc]initWithFrame:CGRectMake(20.0, 25.0, 50.0, 50.0)];
iconView.userInteractionEnabled = NO;
iconView.image = [UIImage imageNamed:@"img.png"];
iconView.layer.masksToBounds = YES;
iconView.layer.cornerRadius = 25.0f;
[cell addSubview:iconView];
}
return cell;
}
很抱歉的混亂，我可以發佈更多的代碼，如果有人想它。
感謝
您正在同步下載主線程上的圖像，這是原因。推薦的方法來處理這是[延遲加載'UITableView'中的圖像]（http://stackoverflow.com/questions/1130089/lazy-load-images-in-uitableview）。 – Amar
你創建了什麼樣的項目？ ARC還是不？ – alinoz
是的，你需要在另一個線程中獲取，但是你的標題是「TableView在幾次上下滾動後放慢速度」，這是由於在你的單元中堆疊了你的視圖，所以這是U必須解決的另一個問題，以及異步下載 – AntonijoDev