使用调度队列在 uitableview 中平滑滚动，在数组中给出随机值

Posted 2023-03-05

【中文标题】使用调度队列在 uitableview 中平滑滚动，在数组中给出随机值

【英文标题】：Using dispatch queue for smooth scrolling in uitableview giving shuffled values in array

【发布时间】：2013-04-09 13:39:50

【问题描述】：

我正在墙上显示帖子，等等，不喜欢按钮必须显示喜欢和不喜欢的数量。帖子的数据同时来自不同的 API。但是喜欢和不喜欢的值来自不同的 API。并且对于每个帖子的不喜欢都有一个 id，该 id 被馈送到 API 然后点击。因此，对于每个帖子，此 API 被点击意味着等于单元格的数量。所以我使用了调度队列，但它在数组中显示了洗牌的值，并且没有调度队列，它给出了正确的值，但是表格在滚动时被暂停并且非常慢。如何解决这个问题，请指导。

这里是代码。

-(UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

static NSString *CellIdentifier = @"Cell";

Cell *cell = (Cell*)[self.mPublicFriendTable dequeueReusableCellWithIdentifier:nil];
if (cell == nil) 
    cell = [[Cell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];

else
    cell = [[Cell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];


cell.contentView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"text_boxbg.png"]];

cell.selectionStyle = UITableViewCellSelectionStyleNone;
cell.mLblName.frame = CGRectMake(50, 9, 150, 18);
cell.mLblTxt.frame = CGRectMake(50, 26, 218, 29);

if (indexPath.section == [self.mArrLike count])

     cell.textLabel.text = @"Load More...";
 else

strLk = [self.mArrLike objectAtIndex:indexPath.section];
strDLk = [self.mArrDislike objectAtIndex:indexPath.section];

   // NSLog(@"mARRUname:%d", [self.mArrUName count]);
cell.mLblName.text = [self.mArrUName objectAtIndex:indexPath.section];
CGSize size = [cell.mLblName.text sizeWithFont:[UIFont boldSystemFontOfSize:20.0]];
cell.mLblImg.frame = CGRectMake(size.width+20,14, 9, 14);

NSString *imageUrlString = [self.mArrProfileImg objectAtIndex:indexPath.section];
NSLog(@"counter at:%d",indexPath.section);
asyncImageView = [[AsyncImageView alloc]initWithFrame:CGRectMake(9, 9, 37, 37)];
[asyncImageView loadImageFromURL:[NSURL URLWithString:imageUrlString]];
[cell.contentView addSubview:asyncImageView];

cell.mLblTxt.text = [self.mArrText objectAtIndex:indexPath.section];
cell.mLblDate.text = [self.mArrDate objectAtIndex:indexPath.section];
cell.mLblTimeImg.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"message.png"]];
cell.mLblDate.textColor = [UIColor colorWithRed:109.0/255.0 green:218.0/255.0 blue:250.0/255.0 alpha:1.0];

[cell.mBtnLike setImage:[UIImage imageNamed:@"thumb_up.png"] forState:UIControlStateNormal];
    [cell.mBtnLike addTarget:self action:@selector(like:) forControlEvents:UIControlEventTouchUpInside];
//[cell.mBtnLike setBackgroundColor:[UIColor colorWithRed:47.0/255.0 green:200.0/255.0 blue:247.0/255.0 alpha:1.0]];
[cell.mBtnLike setTitleEdgeInsets:UIEdgeInsetsMake(0, 0, 0, -10)];
cell.mBtnLike.imageEdgeInsets = UIEdgeInsetsMake(0, -10, 0, 0);
[cell.mBtnLike setTitle:strLk forState:UIControlStateNormal];

[cell.mBtnDislike setImage:[UIImage imageNamed:@"thumb_down.png"] forState:UIControlStateNormal];
[cell.mBtnDislike addTarget:self action:@selector(dislike) forControlEvents:UIControlEventTouchUpInside];
 //[cell.mBtnDislike setBackgroundColor:[UIColor colorWithRed:47.0/255.0 green:200.0/255.0 blue:247.0/255.0 alpha:1.0]];
[cell.mBtnDislike setTitleEdgeInsets:UIEdgeInsetsMake(0, 0, 0, -10)];
cell.mBtnDislike.imageEdgeInsets = UIEdgeInsetsMake(0, -15, 0, 0);
[cell.mBtnDislike setTitle:strDLk forState:UIControlStateNormal];

[cell.mBtnShare setImage:[UIImage imageNamed:@"back_icon.png"] forState:UIControlStateNormal];
[cell.mBtnShare addTarget:self action:@selector(share) forControlEvents:UIControlEventTouchUpInside];
 //[cell.mBtnShare setBackgroundColor:[UIColor colorWithRed:47.0/255.0 green:200.0/255.0 blue:247.0/255.0 alpha:1.0]];
cell.mBtnShare.imageEdgeInsets = UIEdgeInsetsMake(0, 0, 0, -35);
[cell.mBtnShare setTitleEdgeInsets:UIEdgeInsetsMake(0, -50, 0, 0)];
[cell.mBtnShare setTitle:@"" forState:UIControlStateNormal];

[cell.mBtnComm setImage:[UIImage imageNamed:@"chat_icon.png"] forState:UIControlStateNormal];
[cell.mBtnComm addTarget:self action:@selector(comments) forControlEvents:UIControlEventTouchUpInside];
//[cell.mBtnComm setBackgroundColor:[UIColor colorWithRed:47.0/255.0 green:200.0/255.0 blue:247.0/255.0 alpha:1.0]];
[cell.mBtnComm setTitleEdgeInsets:UIEdgeInsetsMake(0, -52, 0, 0)];
cell.mBtnComm.imageEdgeInsets = UIEdgeInsetsMake(0, 0, 0, -50);
[cell.mBtnComm setTitle:@"30" forState:UIControlStateNormal];

return cell;


- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath

  NSLog(@"count like:%d", [self.mArrLike count]);
NSLog(@"count uname:%d", [self.mArrUName count]);
if(indexPath.section == ([self.mArrLike count]-1))

[self loadData:indexPath.section];



-(void)loadData:(int)indexVal;

status = [NSString stringWithFormat:@"get"];
[self.mButtonsStatusDict setObject:status forKey:@"status"];

[self.mButtonsPidDict setObject:[self.mArrPid objectAtIndex:indexVal] forKey:@"pid"];

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);

dispatch_async(queue, ^

    self.mButtonsDict = [MyEventApi likeDislike:self.mButtonsUidDict post:self.mButtonsPidDict postStatus:self.mButtonsStatusDict];
    NSLog(@"buttons data dict:%@", self.mButtonsDict);


    dispatch_sync(dispatch_get_main_queue(), ^

        [self.mArrLike addObject: [self.mButtonsDict valueForKey:@"like"]];
        [self.mArrDislike addObject: [self.mButtonsDict valueForKey:@"dislike"]];

        NSLog(@"arrLike count:%d", [self.mArrLike count]);
       // strLk = [self.mArrLike objectAtIndex:indexPath.section];
       // strDLk = [self.mArrDislike objectAtIndex:indexPath.section];

        [self.mPublicFriendTable reloadData];
    );
);

也尝试了调度队列和异步 json，但没有得到正确的结果。 以上请多多指教。

【参考方案1】：

-在你的 .h 文件中声明变量为int serialIndexVal;

- 维护一个将跟踪 indexVal 的 serialIndexVal...

serialIndexVal++; 
indexVal=serialIndexVal; 

将下面的代码放入 GCD 块中

__block NSString *status = [NSString stringWithFormat:@"get"];
 [self.mButtonsStatusDict setObject:status forKey:@"status"]; 
[self.mButtonsPidDict setObject:[self.mArrPid objectAtIndex:indexVal] forKey:@"pid"];

-On viewWillDisappear 让你的serialIndexVal=0;再次。

【讨论】：

谢谢，但它没有给出预期的结果。

仍然在洗牌？

尝试使用 NSOperationQueue，因为它很难维持 GCD 的执行。***.com/questions/14444041/…

好的，但是我发现了一个关于这个问题的有趣事实，indexVal 的值来自 willDisplayCell 方法，对于获取数组中最多两个值，然后在数组 indexval 的索引 2 处更改为 1并继续。

对，从一开始就有 indexVal 的问题……所以说要把代码放在 GCD 中，无论如何可能发生的是当 GCD 执行一个或其他块时，来自“willDisplayCell”的 indexVal 发生变化和混乱发生...