Question

当我下载每小时预测以及条件图标时，我对iOS和开发天气应用程序相当新。我已经能够使用NSURL Connection实现UICollection。但是，我遇到有关NSURL会话的速度/性能问题。以下是两个问题：

1）下载和呈现下载的图标的速度非常慢（并且图像非常小）。此下载过程可能需要5-10秒。

2）当我按下按钮重置集合时，所有数据都会重置，但现有图像会保留，直到下载新图像为止。这可能需要5-10秒。

这是我的代码：

 - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return self.hours.count;
 }


 - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
static NSString *identifier = @"ConditionsCell";

ConditionsCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];

cell.conditionsTime.text = [self.hours objectAtIndex:indexPath.row];
cell.conditionsTemp.text = [NSString stringWithFormat:@"%@°", [self.hoursTemp objectAtIndex:indexPath.row]];

NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDataTask *dataTask = [session dataTaskWithURL:[NSURL URLWithString:[self.hoursIcons objectAtIndex:indexPath.row]] completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {

    UIImage * serverImage = [UIImage imageWithData: data];
    cell.conditionsImage.image = serverImage;

}];

[dataTask resume];

return cell;

}

这是按钮的IBAction并重新加载CollectionView：

 - (IBAction)selectDay:(UISegmentedControl *)sender {
if (sender.selectedSegmentIndex == 0)
{
    self.todayOrTomorrow = @"today";
}
else if (sender.selectedSegmentIndex == 1)
{
    self.todayOrTomorrow = @"tomorrow";
}

self.hours = [self hours];
self.hoursIcons = [self hoursIcons];
self.hoursTemp = [self hoursTemp];

[_collectionViewHours reloadData];
 }

Answer 1

您正在后台下载数据，但没有在主线程上更新UI，请尝试以下模式，它将帮助您

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
static NSString *identifier = @"ConditionsCell";

ConditionsCollectionViewCell *cell = [collectionView     dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];

cell.conditionsTime.text = [self.hours objectAtIndex:indexPath.row];
cell.conditionsTemp.text = [NSString stringWithFormat:@"%@°", [self.hoursTemp     objectAtIndex:indexPath.row]];
cell.conditionsImage.image = [UIImage imageNamed:""];//reseting image

NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDataTask *dataTask = [session dataTaskWithURL:[NSURL URLWithString:    [self.hoursIcons objectAtIndex:indexPath.row]] completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
@autoreleasepool {//autorelease pool for memory release
if (!error) {
//UIImage * serverImage = [UIImage imageWithData: data];//comment this extra variable and can increase memory overhead.

dispatch_async(dispatch_get_main_queue(), ^{
cell.conditionsImage.image = [UIImage imageWithData: data];//update UI

});

}}//autorelease pool

}];

[dataTask resume];

return cell;
}

它肯定会帮助你完成第一部分。

感谢。

CollectionView NSURL会话速度和重新加载

1 个答案: