从自定义 UICollectionViewCell 获取正确的按钮

Question

我有一个带有自定义 UICollectionViewCell 的自定义 UICollectionView，我的单元格上有一个类似按钮（已连接到 CustomCVCell.h 文件），我需要在按下此按钮时更改它的背景。我所做的是在cellForItemAtIndexPath: 方法上声明按钮的操作，如下所示：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];

    // Configure the cell
    FolderProducts *item = _feedItems[indexPath.item];

    [cell.like addTarget:self action:@selector(likeProduct:) forControlEvents:UIControlEventTouchUpInside];

    return cell;
}

然后在按钮操作上，我尝试像这样更改背景：

- (void)likeProduct:(UIButton *)button {
        [button setImage:[UIImage imageNamed:@"dislike.png"] forState:UIControlStateNormal];
}

它可以工作，但是其他随机单元格的类似按钮的图像发生了变化，我不明白为什么..

我还尝试使用以下方法检索正确的单元格：

CollectionViewCell *cell = (CollectionViewCell *)button.superview.superview;

然后：

[button setImage:[UIImage imageNamed:@"dislike.png"] forState:UIControlStateNormal];

但结果还是错了

Answer 1

问题是由于reusing of the collection view cell 造成的，因为你得到了具有相同图像的随机按钮

解决方案是维护数组并存储liked 按钮的选定索引路径

例如你可以像下面那样做

在CustomCVCell.h中定义一个自定义委托

 #import <UIKit/UIKit.h>

 @class CustomCVCell; //forword decleration
 @protocol CustomCellDelegate <NSObject>  
  - (void)customCell:(CustomCVCell *)cell actionForButton:(UIButton *)inButton; //hear u are passing the cell and the button
 @end


 @interface CustomCVCell : UICollectionViewCell
 @property (weak, nonatomic) IBOutlet UIButton *like ; //a button with outlet
 @property (weak, nonatomic) id<CustomCellDelegate> cellDelegate;// define a custom delegate
 - (IBAction)likeProduct:(UIButton *)sender; // set action to cell not in the controller 

//... other code
 @end

在CustomCVCell.m

#import "CustomCVCell.h"

@implementation CustomCVCell

- (id)initWithFrame:(CGRect)frame
{
   self = [CustomCVCell cell];
   if (self)
   {

   }
   return self;
}

- (void)awakeFromNib {
    // Initialization code
 }

//handle button action in the cell
- (IBAction)likeProduct:(UIButton *)sender
{
   //this action you want it to be in controller, call a delegate method
   if([self.cellDelegate respondsToSelector:@selector(customCell:actionForButton:)])
   {
      [self.cellDelegate customCell:self actionForButton:sender]; //implent the action in the controller 
   }
}

@end

在controller

- (void)viewDidLoad
 {
   [super viewDidLoad];

   UICollectionViewFlowLayout *aFlowLayout = [[UICollectionViewFlowLayout alloc]init];
    //..set up code
   [_aCollectionView registerClass:[CustomCVCell class] forCellWithReuseIdentifier:@"CELL"];

   likedCells = [[NSMutableArray  alloc]init]; //to hold the index paths of the liked cells
 }

//..other code

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

  CustomCVCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"CELL" forIndexPath:indexPath];
  if([likedCells containsObject:indexPath]) //based on the indexaths paths u can set the images of the liked cell and if not set nil
  {
     [cell.like setBackgroundImage:[UIImage imageNamed:@"22.jpg"] forState:UIControlStateNormal];
  }
  else
  {
     [cell.like setBackgroundImage:nil forState:UIControlStateNormal];
  }
  cell.backgroundColor = [UIColor greenColor]; //for testing
  cell.cellDelegate = self; //this must be important
  return cell;
}

//as the like button cliks this method will trigger since u are passing the cell and the button, u can get the index path of the cell 
- (void)customCell:(CustomCVCell *)cell actionForButton:(UIButton *)inButton
{
 //hear u will get both cell and its button
 //[inButton setImage:[UIImage imageNamed:@"22.jpg"] forState:UIControlStateNormal];
 [inButton setBackgroundImage:[UIImage imageNamed:@"22.jpg"] forState:UIControlStateNormal]; //set the image
 [likedCells addObject: [_aCollectionView indexPathForCell:cell]]; //and store the index path in the likedCells array
}

如果你想反转操作同样删除索引路径就是这样

Answer 2

基本思路是需要将buttons坐标空间转换为collectionviews坐标空间，然后获取indexPath。

如果你需要使用 Objective-C，让我们创建一个返回给定单元格子视图的 indexPath 的函数：

- (NSIndexPath *)indexPathForCellContainingView:(UIView *)view inCollectionView:(UICollectionView *)collectionView {
    CGPoint viewCenterRelativeToCollectionView = [collectionView convertPoint:CGPointMake(CGRectGetMidX(view.bounds), CGRectGetMidY(view.bounds)) fromView:view];
    NSIndexPath *cellIndexPath = [collectionView indexPathForItemAtPoint:viewCenterRelativeToCollectionView];
    return cellIndexPath
}

现在在您的按钮处理程序中：

- (void)likeProduct:(UIButton *)button {
    [button setImage:[UIImage imageNamed:@"dislike.png"] forState:UIControlStateNormal];
    NSIndexPath *buttonIndexPath = [self indexPathForCellContainingView:button];
    UICollectionViewCell *tappedCell = [collectionView cellForItemAtIndexPath:buttonIndexPath];
}

请记住，当您的单元格滚动到边界之外时，它将被重复使用，因此您肯定需要跟踪此状态。要么将其持久化到磁盘，要么拥有一个简单的 NSDictionary 来管理每个按钮的状态。

我在 Swift 中有一个方便的Gist，它也正好解决了 UICollectionView 和 UITableView 的问题。

here和here也有类似的问题

Answer 3

为您的按钮分配一个标签以识别它。

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];

    // Configure the cell
    FolderProducts *item = _feedItems[indexPath.item];

    [cell.like addTarget:self action:@selector(likeProduct:) forControlEvents:UIControlEventTouchUpInside];
cell.like.tag = indexPath.item;

    return cell;
}

然后在实现方法中添加如下代码，

- (void)likeProduct:(UIButton *)button {
        UIButton *btn = (UIButton *)sender;
        [button setImage:[UIImage imageNamed:@"dislike.png"] forState:UIControlStateNormal];
}

注意：实现多选/单选的最佳方式是通过与您的喜好相关联的 id。使用集合视图存储该 ID，然后从按钮方法重新加载表格。

如果您还需要更多帮助，请告诉我..

Answer 4

您可以在选择器中设置按钮标签和检索标签。

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView    cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];

    // Configure the cell
    FolderProducts *item = _feedItems[indexPath.item];

    cell.like.tag = indexPath.item

    [cell.like addTarget:self action:@selector(likeProduct:) forControlEvents:UIControlEventTouchUpInside];

    return cell;

} 

Answer 5

因为您没有为单元格中的按钮设置标签。所以这些都是一次选择的。您可以设置他们的标签，如 indexPath.item 并在 didSelectItemAtIndexPath 中捕获他们的标签并选择所需的项目。