ios - 使用通过点击 API 获得的响应进行填充时， Collection View 会卡住很长时间

Question

我正在尝试从服务器获取数据并使用该数据填充 Collection View 单元格，但是当 Collection View 被填充时卡住并且需要很长时间才能滚动。

到底出了什么问题？

-(void)callService:(NSNumber*)categoryid{
    AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
    manager.responseSerializer = [AFJSONResponseSerializer
                                  serializerWithReadingOptions:NSJSONReadingAllowFragments];

    [manager.requestSerializer setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    manager.responseSerializer.acceptableContentTypes = [manager.responseSerializer.acceptableContentTypes setByAddingObject:@"text/html"];
    NSMutableDictionary *dict = [NSMutableDictionary new];
    [dict setValue:@1 forKey:@"page"];
    [dict setValue:@25 forKey:@"limit"];

  [dict setValue:categoryid forKey:@"category_id"];

    [manager POST:@"https://www.foodfuels.com/Api/getrecipes"
       parameters:dict progress:nil success:^(NSURLSessionTask *task,id responseObject)
     {
         int status = [[responseObject objectForKey:@"status"] intValue];

         if(status == 200)
         {
             responseArray = [responseObject valueForKey:@"data"];

             dispatch_async(dispatch_get_main_queue(), ^{
                 [MBProgressHUD hideHUDForView:self.view animated:true];
                 [_outerCollectionView reloadData];

             });
         }

         else
         {
             [[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"logininfo"];
             UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"Error" message:@"some eror!"  delegate:self cancelButtonTitle:Nil otherButtonTitles:@"Ok", nil];
             [alert show];
         }
         dispatch_async(dispatch_get_main_queue(), ^{

          //[MBProgressHUD hideHUDForView:self.view animated:YES];

         });

     }
          failure:^(NSURLSessionTask *operation, NSError *error)
     {         
         UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"Error" message:error.localizedDescription delegate:self cancelButtonTitle:Nil otherButtonTitles:@"Ok", nil];

         [alert show];

         dispatch_async(dispatch_get_main_queue(), ^{

           //  [MBProgressHUD hideHUDForView:self.view animated:YES];

         });

     }];

}

Collection View

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
    if(collectionView==_headingCollectionView){
        recipeHeading = (RecipeHeadingCell*)[collectionView dequeueReusableCellWithReuseIdentifier:@"headingCell" forIndexPath:indexPath];
        _headingCollectionView.delegate = self;
        [recipeHeading.headingBtn setTitle:[recipeTypeArray objectAtIndex:indexPath.row] forState:UIControlStateNormal];
        [recipeHeading.headingBtn addTarget:self action:@selector(doSomething:) forControlEvents:UIControlEventTouchUpInside];

        bool d = [allValues[indexPath.row] boolValue];

        if(d)
        {
            [recipeHeading.headingBtn setTitleColor:[UIColor colorWithRed:36/255.0 green:71/255.0 blue:113/255.0 alpha:1.0] forState:UIControlStateNormal];            [recipeHeading.headingBtn addSubview:bottomBorder];
        }
        else
        {
            [recipeHeading.headingBtn setTitleColor:[UIColor whiteColor]forState:UIControlStateNormal];
        }

        return recipeHeading;
    }
    else if (collectionView==_outerCollectionView){
        RecipeOuterCell *outerCell =(RecipeOuterCell*)[collectionView dequeueReusableCellWithReuseIdentifier:@"outerCell" forIndexPath:indexPath];
        return outerCell;
    }
    else{
        RecipeInnerCell *innerCell = (RecipeInnerCell*)[collectionView dequeueReusableCellWithReuseIdentifier:@"innerCell" forIndexPath:indexPath];
        [innerCell populateRecipeScreen:responseArray index:indexPath];
        return innerCell;

    }
}

内部 Collection View 单元格

-(void)populateRecipeScreen:(NSArray*)recipeResponseArr index:(NSIndexPath*)path{
    NSLog(@"the value of recipe array are as follows %@",recipeResponseArr);
    for(int i=0;i<recipeResponseArr.count;i++){
        self.comment_Count.text =[[[recipeResponseArr valueForKey:@"comment_count"]objectAtIndex:path.row]stringValue];
        self.titleLbl.text =[[recipeResponseArr valueForKey:@"description"]objectAtIndex:path.row];
        self.like_Count.text = [[[recipeResponseArr valueForKey:@"like_count"]objectAtIndex:path.row]stringValue];
        NSData *data= [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString: [[[recipeResponseArr valueForKey:@"user"]valueForKey:@"image"]  objectAtIndex:path.row]]];
        ;            self.smallImgView.image=[UIImage imageWithData:data];

        self.share_Count.text = [[[recipeResponseArr valueForKey:@"share_count"]objectAtIndex:path.row]stringValue];
        self.subTitleLbl.text = [[[recipeResponseArr valueForKey:@"user"]valueForKey:@"username"]  objectAtIndex:path.row];
        NSLog(@"url obtained as result %@",[[[recipeResponseArr valueForKey:@"upload_images"]valueForKey:@"name"]  objectAtIndex:path.row]);
        NSArray *urlString = [[[recipeResponseArr valueForKey:@"upload_images"]valueForKey:@"name"]  objectAtIndex:path.row];

        NSData *mainData=[[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:[urlString objectAtIndex:0]]];
        self.mainImg.image=[UIImage imageWithData:mainData];
    }
}

Answer 1

您似乎正在通过 initWithContentsOfURL: 在主线程中从网络加载图像(即从 recipeResponseArr["user"]["image"] 加载图像。强烈建议不要这样做，并且最好不要这样做。来自文档:

Important

Don't use this synchronous method to request network-based URLs. For network-based URLs, this method can block the current thread for tens of seconds on a slow network, resulting in a poor user experience, and in iOS, may cause your app to be terminated.

Instead, for non-file URLs, consider using the dataTaskWithURL:completionHandler: method of the NSURLSession class. See URL Session Programming Guide for details.

如果您需要有效且简单的工具来加载图像，我建议您使用 SDWebImage或 AlamofireImage