在第一次加载视图时预选择/突出显示UICollectionViewCell [英] pre select/highlight UICollectionViewCell on first load of view

问题描述

我试图在UICollectionView中预先选择第一个对象/ UICollectionViewCell？我试过了：

Im trying to preselect the first object/UICollectionViewCell in the UICollectionView? I have tried:

self.dateCollectionView.allowsMultipleSelection=NO;

[self.dateCollectionView selectItemAtIndexPath:0 animated:YES scrollPosition:UICollectionViewScrollPositionLeft];
[self collectionView:self.dateCollectionView didSelectItemAtIndexPath:0];
[self.dateCollectionView reloadData];

在 viewDidLoad 。

这是我的 UICollectionView 方法;

 -(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{

  return self.titles.count;
 }

 -(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{

    UICollectionViewCell * cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
    cell.backgroundColor= [UIColor clearColor];
    UILabel * dateLabel = (UILabel *)[cell viewWithTag:1];
    UILabel * subText = (UILabel *)[cell viewWithTag:2];
    subText.text=self.titles[indexPath.row];
    subText.adjustsFontSizeToFitWidth=YES;
    if (cell.selected) {
        cell.backgroundColor = [UIColor blueColor]; // highlight selection
    }
    else
    {
        cell.backgroundColor = [UIColor redColor]; // Default color
    }
    return cell;
}

-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath  {

    UICollectionViewCell *datasetCell =[collectionView cellForItemAtIndexPath:indexPath];
    datasetCell.backgroundColor = [UIColor blueColor]; // highlight selection
}

-(void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath {

 UICollectionViewCell *datasetCell =[collectionView cellForItemAtIndexPath:indexPath];
datasetCell.backgroundColor = [UIColor redColor]; // Default color
}

- (BOOL)collectionView:(UICollectionView *)collectionView
 shouldHighlightItemAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}

- (BOOL)collectionView:(UICollectionView *)collectionView
 shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath;
{
    return YES;
}

推荐答案

在 viewDidAppear ：

NSIndexPath *indexPathForFirstRow = [NSIndexPath indexPathForRow:0 inSection:0];
[self.dateCollectionView selectItemAtIndexPath:indexPathForFirstRow animated:NO scrollPosition:UICollectionViewScrollPositionNone];
[self collectionView:self.dateCollectionView didSelectItemAtIndexPath:indexPathForFirstRow];

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