如何在集合视图中单个 select 单元格..？

Question

这些代码可以正常工作，但是当我滚动我的集合视图时，另一个单元格也会 selected，例如有 18 张图像可用，首先在运行显示六张当我将 select 任何一个位置然后下一个六位置图像自动 select 的时候。为什么一次有两个单元格 selecting 我在这里感到困惑。请给我解决方案

这里我在主要节目分镜中拍摄了 6 个单元格

UICollectionViewFlowLayout *flowLayout = (UICollectionViewFlowLayout*)self.collectionView.collectionViewLayout;

flowLayout.minimumLineSpacing = 15;
CGFloat availableWidthForCells = CGRectGetWidth(self.collectionView.frame) - flowLayout.sectionInset.left - flowLayout.sectionInset.right - flowLayout.minimumInteritemSpacing *2;

cellWidth = availableWidthForCells /6;
    NSLog(@"cellWidth:%f",cellWidth);
flowLayout.itemSize = CGSizeMake(cellWidth, cellWidth);

这是我的Didselect和didDeselect方法

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

    UICollectionViewCell* cell = [collectionView cellForItemAtIndexPath:indexPath];

    cell.layer.cornerRadius = cellWidth / 2.0;
    cell.layer.backgroundColor = [UIColor blackColor].CGColor;
    NSLog(@"INDEXPATH:-%ld",(long)indexPath.row);
}
-(void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath{

    UICollectionViewCell* cell = [collectionView cellForItemAtIndexPath:indexPath];
    cell.layer.cornerRadius = cellWidth / 2.0;
    cell.layer.backgroundColor = [UIColor whiteColor].CGColor;

}

Answer 1

那是因为细胞被重复使用了。当你

UICollectionViewCell* cell = [collectionView cellForItemAtIndexPath:indexPath];

改变单元格的角半径，实际上改变了不止一个单元格的角半径。所以你应该这样做：

let cell = collectionView.dequeueReusableCellWithReuseIdentifier("YourCell", forIndexPath: indexPath) as! YourCell

Answer 2

发生这种情况是因为 collectionView 重用了单元格；

您应该将所选单元格的 IndexPath 存储在一个变量中：

ObjC:

@property (nonatomic, retain) NSIndexPath *selectedIndexPath;

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

    UICollectionViewCell* cell = [collectionView cellForItemAtIndexPath:indexPath];

    cell.layer.backgroundColor = [UIColor blackColor].CGColor;
    NSLog(@"INDEXPATH:-%ld",(long)indexPath.row);

    self.selectedIndexPath = indexPath
}
-(void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath{

    UICollectionViewCell* cell = [collectionView cellForItemAtIndexPath:indexPath];
    cell.layer.backgroundColor = [UIColor whiteColor].CGColor;

    self.selectedIndexPath = nil
}

Swift :

var selectedIndexPath: IndexPath?

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    let cell = collectionView.cellForItem(at: indexPath)

    cell.layer.backgroundColor = UIColor.black

    self.selectedIndexPath = indexPath
}

func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
    let cell = collectionView.cellForItem(at: indexPath)

    cell.layer.backgroundColor = UIColor.white

    self.selectedIndexPath = nil
}

比 "cell for row at indexPath" 检查：

ObjC:

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

    UICollectionViewCell* cell = [collectionView cellForItemAtIndexPath:indexPath];
    cell.layer.cornerRadius = cellWidth / 2.0;
    if (self.selectedIndexPath != nil && indexPath == self.selectedIndexPath) {
        cell.layer.backgroundColor = [UIColor blackColor].CGColor;
    else {
        cell.layer.backgroundColor = [UIColor whiteColor].CGColor;
   }

    return cell
}

Swift :

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let cell = collectionView.cellForItem(at: indexPath)
    cell.layer.cornerRadius = cellWidth / 2

    if self.selectedIndexPath != nil && indexPath == self.selectedIndexPath {
        cell.layer.backgroundColor = UIColor.black
    else {
        cell.layer.backgroundColor = UIColor.white
    }
}

Answer 3

感谢 Alberto Scampini 此代码用于 swift 3.1

var selectedIndexPath: IndexPath?

 func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let cell = self.collectionView.dequeueReusableCell(withReuseIdentifier: "SegmentChoiceCVCell", for: indexPath) as! SegmentChoiceCVCell
    //configure cell

    if selectedIndexPath != nil && indexPath == selectedIndexPath {
        cell.checkIcon.backgroundColor = UIColor.black

    }else{

        cell.checkIcon.backgroundColor = UIColor.white
    }

    return cell

}



func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

    let cell = collectionView.cellForItem(at: indexPath) as! SegmentChoiceCVCell

        cell.checkIcon.backgroundColor = UIColor.black
    self.selectedIndexPath = indexPath

}

func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
    let cell: SegmentChoiceCVCell = collectionView.cellForItem(at: indexPath) as! SegmentChoiceCVCell

        cell.checkIcon.backgroundColor = white
    selectedIndexPath = nil
}

Answer 4

我知道我迟到了。我有同样的问题。在 Whosebug 中环顾四周之后。这是我的解决方案。它可以帮助初学者更容易理解 UICollectionViewCell。

“cellForItemAtIndexPath”方法控制单元格的显示方式。屏幕外的单元格将不会更新。

Swift 4

首先，您需要 class 您的手机。

class SubclassedCell: UICollectionViewCell {

      @IBOutlet var cellImage: UIImageView!
      @IBOutlet var cellCaption: UILabel!

}

extension SubclassedCell{

   func highlightEffect(){
      self.layer.borderWidth = 3.0
      self.layer.borderColor = UIColor.lightGray.cgColor
   }

   func removeHighlight(){
      
      self.layer.borderColor = UIColor.clear.cgColor
   }

}

现在是“cellForItemAt”方法。

   func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    
    
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "blahblahblah", for: indexPath) as! SubclassedCell
  
    
    cell.cellImage.image = yourImages[indexPath.item]
    cell.cellCaption.text = yourImageNames[indexPath.item]
    cell.removeHighlight()  // Call subclassed cell method.
    if indexPath.item == selectedItem {
        cell.highlightEffect() // Call subclassed cell method.
        preSelected = IndexPath(item: indexPath.item, section: indexPath.section)
        
        
    }
    
    collecttionRef = collectionView
    return cell
    
}

然后，对于“didSelectItemAt”方法

  func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath){
    
    collectionView.allowsMultipleSelection = false
    if let cell = collectionView.cellForItem(at: indexPath) as! SubclassedCell?{
        let indexPathData = NSKeyedArchiver.archivedData(withRootObject: indexPath)
        UserDefaults.standard.set(indexPathData,forKey: "backgroundIndexPath")
        //I got some unwrapped crash for my App so I have to use UserDefault to fix the unwrapped problem. You could ignore these both lines.

        selectedItem = indexPath.item //selectedItem is used in the "cellForItemAt" method above.
        
        

        collectionView.reloadData() //update all cells. It could be heavy if you have many cells.
        
    }
   
}

如何在集合视图中单个 select 单元格..？

how to single select cell in collection view..?

ios

uicollectionview

Swift 4