我正在制作一个应用程序，其中我从服务器和数据图像路径中获取数据也即将到来，但当我将图像设置为我的tableview单元格应用程序将变得太沉重可能bi我没有正确设置图像下面是我的样本代码提前代码：）
(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
static NSString *tableviewidentifier = @"cell";
tablecellTableViewCell *cell= [self.activitiesTableView_ dequeueReusableCellWithIdentifier:tableviewidentifier];
if(cell==nil)
{
cell = [[tablecellTableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:tableviewidentifier];
}if(indexPath.row == [self tableView:tableView numberOfRowsInSection:indexPath.section] - 1){
// [[cell textLabel] setText:@"Load more records"];
}
UILabel *valuedate = (UILabel *)[cell viewWithTag:21];
UILabel *msg = (UILabel *)[cell viewWithTag:22];
UILabel *date = (UILabel *)[cell viewWithTag:23];
UILabel *time = (UILabel *)[cell viewWithTag:24];
valuedate.text=[[self.inboxmessagesarray objectAtIndex:indexPath.row]objectForKey:@"offerTitle"];
msg.text=@"How are you?";
NSString *img=[[self.inboxmessagesarray objectAtIndex:indexPath.row]objectForKey:@"offerPhoto"];// here i am getting image path
UIImage *img1 = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:img]]];
cell.imageView.image=img1;// here i am setting image due to which app is so heavy and stuck
return cell;
}
答案 0 :(得分：2)
请勿使用imageWithData:来设置图片。它是同步的，会让你的应用运行缓慢。
而不是使用SDWebImage
你只需要做以下事情：
将SDWebImage文件夹转储到您的项目中。
导入UIImageView+WebCache.h。
使用以下设置图片：sd_setImageWithURL:
OR
GCD (Grand Central Dispatch) and sending asynchronous requests。代码从HERE复制。
首先实现以下方法。
- (void)downloadImageWithURL:(NSURL *)url completionBlock:(void (^)(BOOL succeeded, UIImage *image))completionBlock
{
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
if ( !error )
{
UIImage *image = [[UIImage alloc] initWithData:data];
completionBlock(YES,image);
} else{
completionBlock(NO,nil);
}
}];
}
然后在cellForRowAtIndexPath
[self downloadImageWithURL:your_url completionBlock:^(BOOL succeeded, UIImage *image) {
if (succeeded) {
// change the image in the cell
cell.imageView.image = image;
}
}];
答案 1 :(得分：1)
首先，您调用dataWithContentsOfURL：函数，这将使应用程序无响应，因为您在主线程上调用它。要使其响应，您需要创建一个自定义单元格YourCell并在YourCell.h中声明一个方法
@interface YourCell : UITableViewCell
{
UIImage *_cImage;
}
- (void)downloadImageFromURL:(NSURL *)imageUrl;
@end
现在在YourCell.m中你需要这样做：
- (void)downloadImageFromURL:(NSURL *)imageUrl
{
if (_cImage != nil)
{
self.imageView.image = _cImage;
}
else
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
_cImage = [UIImage imageWithData:[NSData dataWithContentsOfURL:imageUrl]];
dispatch_sync(dispatch_get_main_queue(), ^{
self.imageView.image = _cImage;
});
});
}
}
现在来自cellForRowAtIndexPath：您只需要调用downloadImageFromURL：YourCell的函数并将imageUrl传递给它，并负责下载并显示图像。
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier= @"YourCell";
YourCell *cell = (YourCell *)[self.activitiesTableView_ dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[NSBundle mainBundle] loadNibNamed:@"YourCell" owner:self options:nil] objectAtIndex:0];
}
// Set your UILabels as before.....
NSString *imagePath=[[self.inboxmessagesarray objectAtIndex:indexPath.row] objectForKey:@"offerPhoto"];
[cell downloadImageFromURL:[NSURL URLWithString:imagePath]];
return cell;
}
如果您有任何问题，请与我们联系。
答案 2 :(得分：1)
尝试以下代码，希望这有助于你。
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
__block tablecellTableViewCell *cell= [self.activitiesTableView_ dequeueReusableCellWithIdentifier:tableviewidentifier];
if(cell==nil)
{
cell = [[tablecellTableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:tableviewidentifier];
}
if(indexPath.row == [self tableView:tableView numberOfRowsInSection:indexPath.section] - 1)
{
// [[cell textLabel] setText:@"Load more records"];
}
UILabel *valuedate = (UILabel *)[cell viewWithTag:21];
UILabel *msg = (UILabel *)[cell viewWithTag:22];
UILabel *date = (UILabel *)[cell viewWithTag:23];
UILabel *time = (UILabel *)[cell viewWithTag:24];
valuedate.text=[[self.inboxmessagesarray objectAtIndex:indexPath.row]objectForKey:@"offerTitle"];
msg.text=@"How are you?";
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
NSString *img=[[self.inboxmessagesarray objectAtIndex:indexPath.row]objectForKey:@"offerPhoto"];// here i am getting image path
NSURL *url = [NSURL URLWithString:img];
NSData * imageData = [NSData dataWithContentsOfURL:url];
UIImage *image = [UIImage imageWithData:imageData];
dispatch_sync(dispatch_get_main_queue(), ^{ //in main thread update the image
cell.imageView.image = image;
cell.textLabel.text = @""; //add this update will reflect the changes
});
});
return cell;
}
修改 为了重复使用下载的图像，您可以将它们保存在磁盘上，或者只是将它们保存在某些位置，例如在字典中用于临时使用
在下面的代码中我采用了一个示例字典，强大的下载图像以行为键
@interface ViewController ()
{
NSMutableDictionary *imagesDictionary; //lets declare a mutable dictionary to hold images
}
在这个方法中只是初始化它
- (void)viewDidLoad {
[super viewDidLoad];
// rest of your code
//...........
//
imagesDictionary = [[NSMutableDictionary alloc]init]; //initilise
}
此方法只是将下载的图像添加到字典中，以便将相应的行作为键
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
__block tablecellTableViewCell *cell= [self.activitiesTableView_ dequeueReusableCellWithIdentifier:tableviewidentifier];
if(cell==nil)
{
cell = [[tablecellTableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:tableviewidentifier];
}
if(indexPath.row == [self tableView:tableView numberOfRowsInSection:indexPath.section] - 1)
{
// [[cell textLabel] setText:@"Load more records"];
}
__block NSString *row = [NSString stringWithFormat:@"%d",indexPath.row]; //add this
UILabel *valuedate = (UILabel *)[cell viewWithTag:21];
UILabel *msg = (UILabel *)[cell viewWithTag:22];
UILabel *date = (UILabel *)[cell viewWithTag:23];
UILabel *time = (UILabel *)[cell viewWithTag:24];
// valuedate.text=[[self.inboxmessagesarray objectAtIndex:indexPath.row]objectForKey:@"offerTitle"];
msg.text=@"How are you?";
if(![[imagesDictionary allKeys] containsObject:row]) //if image not found download and add it to dictionary
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
// NSString *img=[[self.inboxmessagesarray objectAtIndex:indexPath.row]objectForKey:@"offerPhoto"];// here i am getting image path
NSURL *url = [NSURL URLWithString:img];
NSData * imageData = [NSData dataWithContentsOfURL:url];
UIImage *image = [UIImage imageWithData:imageData];
dispatch_sync(dispatch_get_main_queue(), ^{ //in main thread update the image
[imagesDictionary setObject:image forKey:row]; //sorry, while editing to your code i forgot to add this
cell.imageView.image = image;
cell.textLabel.text = @""; //add this update will reflect the changes
NSLog(@"loading and addig to dictionary");
});
});
}
else
{
cell.imageView.image = [imagesDictionary objectForKey:row];
NSLog(@"retriving from dictioary");
}
return cell;
}
答案 3 :(得分：0)
UIImageView *img1 = (UIImageView *)[cell viewWithTag:104];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
dispatch_async(dispatch_get_main_queue(), ^{
img1.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:img]]];
});
});
发送图像的异步请求。在图像加载之前，执行此操作不会阻止UI。