如何使用SDWebImage

我已经UITableViewCell在其中加载图片，因此我要图片加载异步并显示激活指示器。这次图像加载时间非常长，并且所有图像均在表视图中显示图像后加载。很多时候图像无法加载并且用户UIInterface挂起。并且在应用程序中不运行任何进程。.我很累，我使用了一个SDWebImage库。请帮助怎么可能，谢谢

#import "UIImageView+WebCache.h"

@interface pictureViewController ()
{
    NSArray*picarray;
    NSArray*titlearray;
    NSArray*idarray;
}

@end

@implementation pictureViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    [[[self navigationController] navigationBar] setTitleTextAttributes:@{NSForegroundColorAttributeName: [UIColor whiteColor]}];

    [[UINavigationBar appearance] setBackgroundImage:[UIImage imageNamed:@"background2.png"] forBarMetrics:UIBarMetricsDefault];

    _tableview.separatorColor = [UIColor yellowColor];

    NSURLRequest *req=[[NSURLRequest alloc]initWithURL:[NSURL URLWithString:@"http://edutimeapp.com/toshow/chamber-of-commerc/ws/fetch_gallery.php"]];
    response =[[NSMutableData alloc]init];
    [NSURLConnection connectionWithRequest:req delegate:self];
}

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [response appendData:data];
    NSLog(@"error receving data %@",response);
}

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{

}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
     NSError *error;

     //NSLog(@"Error in receiving data %@",error);
     NSMutableDictionary *json = [NSJSONSerialization JSONObjectWithData:response options:NSJSONReadingMutableLeaves  error:&error];
     // NSLog(@"response data %@",json);

      NSArray *results = [json objectForKey:@"status"];
      picarray = [results valueForKey:@"img_url"];
      titlearray = [results valueForKey:@"title"];
      // NSLog(@"my title is%@",titlearray);
      idarray=[results valueForKey:@"id"];
      //NSLog(@"my galary id is%@",idarray);
      [self.tableview reloadData];
}


// Do any additional setup after loading the view, typically from a nib.
- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [picarray count];
}


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    // NSLog(@"tableview cell");
    picture_viewcontrollerCell *cell = [tableView dequeueReusableCellWithIdentifier:@"htr"];
    if (cell==nil)
    {
        NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"Cell" owner:self options:nil];
        cell = [nib objectAtIndex:0];
    }

     //NSData* imageData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString: [picarray objectAtIndex:indexPath.row]]];
    // UIImage* image = [[UIImage alloc] initWithData:imageData];
    //cell.picture.image =image;

    cell.titlelbl.text=[NSString stringWithFormat:@"%@",[titlearray objectAtIndex:indexPath.row]];

    NSURL*url= [[picarray objectAtIndex:indexPath.row]valueForKey:@"img_url"];
    [cell.picture setContentMode:UIViewContentModeScaleAspectFill];
    [cell.picture sd_setImageWithURL:url placeholderImage:[UIImage imageNamed:@"Placeholder.jpg"]];


    return  cell;
}

@end