如何在集合视图中单选单元格？

Question

这是正常工作的代码，但是当我将滚动我的集合视图，然后另一个单元格也被选中，例如18个图像可用，并且在运行时首先显示六个，当我将选择六个中的任何一个然后还选择另一个2细胞我在这里混淆为什么另外两个细胞已经选择请给我解决方案

这里我在主要展示故事板上采取了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

这是因为collectionView重用了单元格;

您应该将选定单元格的IndexPath存储在变量中：

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
}

斯威夫特：

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
}

而不是“indexPath中行的单元格”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
}

斯威夫特：

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 2

感谢Alberto Scampini 此代码适用于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 3

我知道我迟到了。我有同样的问题。之后在stackoverflow中查看。这是我的解决方案。它可能有助于初学者更容易理解UICollectionViewCell。

＆＃34; cellForItemAtIndexPath＆＃34;方法控制单元格的显示方式。屏幕外的单元格不会更新。

Swift 4

首先，您需要对细胞进行细分。

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
   }

} 

现在为＆＃34; cellForItemAt＆＃34;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＆＃34; didSelectItemAt＆＃34;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.

    }

}

Answer 4

那是因为细胞正在重复使用。当你

UICollectionViewCell* cell = [collectionView cellForItemAtIndexPath:indexPath];

并更改单元格的圆角半径，实际上您更改了多个单元格的圆角半径。所以你应该这样做：

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