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标题: ios - UICollectionView 上的可重用性问题 [打印本页]

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作者: 菜鸟教程小白    时间: 2022-12-13 07:24
标题: ios - UICollectionView 上的可重用性问题

我曾使用过 UITableView，但我从未在我的应用程序中使用过 UICollectionView。所以我想以编程方式创建 UICollectionView。

以下是我的代码:

UICollectionViewFlowLayout *layout =[[UICollectionViewFlowLayout alloc] init];
    _collectionView=[[UICollectionView alloc] initWithFrame:CGRectMake(0, 43, self.view.frame.size.width, self.view.frame.size.height - 84) collectionViewLayout:layout];
    [_collectionView setDataSource:self];
    [_collectionView setDelegate:self];
    [_collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier"cellIdentifier"];
    layout.sectionInset = UIEdgeInsetsMake(5, 5, 5, 5);
    layout.minimumInteritemSpacing = 5;
    [_collectionView setBackgroundColor:self.view.backgroundColor];        
    [self.view addSubview:_collectionView];

委托(delegate)和数据源方法。

#pragma mark -
#pragma mark - UITableView Delegate Methods

- (NSInteger)collectionViewUICollectionView *)collectionView numberOfItemsInSectionNSInteger)section
{
    return 15;
}

- (UICollectionViewCell *)collectionViewUICollectionView *)collectionView cellForItemAtIndexPathNSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier"cellIdentifier" forIndexPath:indexPath];

    if (cell.selected)
        cell.backgroundColor = [UIColor lightGrayColor]; // highlight selection cell
    else
        cell.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed"background-grid.png"]]; // Default Cell

    UIImageView *imgPhoto = [[UIImageView alloc] init];
    imgPhoto.userInteractionEnabled = YES;
    imgPhoto.backgroundColor = [UIColor grayColor];
    imgPhoto.frame =  CGRectMake(3.5, 5, 90, 80);
    imgPhoto.clipsToBounds = YES;
    imgPhoto.image = [UIImage imageNamed"product.png"];
    [cell.contentView addSubview:imgPhoto];

    UILabel *lblCategoryTitle = [[UILabel alloc] init];
    [lblCategoryTitle  setFont: [UIFont fontWithName"OpenSans-Bold" size:14]];
    lblCategoryTitle.textAlignment = NSTextAlignmentCenter;
    lblCategoryTitle.frame = CGRectMake(3.5, 90, 90, 24);
    lblCategoryTitle.textColor = [UIColor blackColor];
    lblCategoryTitle.text = @"roduct 1"; 
    lblCategoryTitle.backgroundColor = [UIColor clearColor];
    lblCategoryTitle.numberOfLines = 2;
    [cell.contentView addSubview:lblCategoryTitle];

    return cell;
}

- (CGSize)collectionViewUICollectionView *)collectionView layoutUICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPathNSIndexPath *)indexPath
{
    return CGSizeMake(97, 118);
}

-(void)collectionViewUICollectionView *)collectionView didSelectItemAtIndexPathNSIndexPath *)indexPath  {

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

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

    UICollectionViewCell *datasetCell =[collectionView cellForItemAtIndexPath:indexPath];
    datasetCell.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed"background-grid.png"]]; // default cell
}

然后我的屏幕看起来像

问题 1 -查看上面的屏幕，您会看到第 1 和第 3 项看起来很模糊(请参阅 产品 1) 然后是第 2 项/中间项目？为什么会这样？

每当我向上/向下滚动 UICollectionView 时，项目都会被覆盖，查看下一张图片

看了这张图片后，根据我对 UITableView 的经验，它的发生是因为 UICollectionView 的单元格的可重用性。

问题 2 - 那我该如何解决呢？

请给我你的建议并帮助我解决这个问题。

已编辑: (@Dima 的建议)

自定义单元格

.h 文件

#import <UIKit/UIKit.h>

@interface customeGridCell : UICollectionViewCell

@property (nonatomic, strong) UIImageView *imgPhoto;
@property (nonatomic, strong) UILabel *lblCategoryTitle;

@end

.m 文件

#import "customeGridCell.h"

@implementation customeGridCell

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self)
    {
        self.imgPhoto = [[UIImageView alloc] init];
        self.imgPhoto.userInteractionEnabled = YES;
        self.imgPhoto.backgroundColor = [UIColor grayColor];
        self.imgPhoto.frame =  CGRectMake(3.5, 5, 90, 80);
        [self addSubview:self.imgPhoto];

        self.lblCategoryTitle = [[UILabel alloc] init];
        [self.lblCategoryTitle  setFont: [UIFont fontWithName"OpenSans-Bold" size:14]];
        self.lblCategoryTitle.textAlignment = NSTextAlignmentCenter;
        self.lblCategoryTitle.frame = CGRectMake(3.5, 90, 90, 24);
        self.lblCategoryTitle.textColor = [UIColor blackColor];
        self.lblCategoryTitle.backgroundColor = [UIColor clearColor];
        self.lblCategoryTitle.numberOfLines = 2;
        [self addSubview:self.lblCategoryTitle];
    }
    return self;
}

及cellForItemAtIndexPath的代码

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    customeGridCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier"cellIdentifier" forIndexPath:indexPath];

    if (cell.selected)
        cell.backgroundColor = [UIColor lightGrayColor]; // highlight selection cell
    else
        cell.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed"background-grid.png"]]; // Default Cell


    cell.imgPhoto.image =  [UIImage imageNamed"product.png"];
    cell.lblCategoryTitle.text = @"roduct 1";

    return cell;
}

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Best Answer-推荐答案

问题出在您的 collectionView:cellForItemAtIndexPath: 方法中。每次重用单元格时，您都在添加这些 subview ，彼此叠加。

您应该创建一个 UICollectionViewCell 子类并将所有您想要的额外 subview 添加到它的初始化程序中。这将确保它们只被添加一次。

示例代码:

这是一个示例，说明如何将 UICollectionViewCell

子类化

@interface MyCustomCell : UICollectionViewCell

@property (nonatomic, strong) UILabel *customLabel;
@property (nonatomic, strong) UIImageView *customImageView;
@end


// in implementation file
- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) 
    {
        // initialize label and imageview here, then add them as subviews to the content view
    }
    return self;
}

然后，当您抓取一个单元格时，您只需执行以下操作:

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    MyCustomCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"cellIdentifier" forIndexPath:indexPath];

    if (cell.selected)
        cell.backgroundColor = [UIColor lightGrayColor]; // highlight selection cell
    else
        cell.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"background-grid.png"]]; // Default Cell

    cell.customImageView.image = // whatever
    cell.customLabel.text = // whatever

    return cell;
}

关于ios - UICollectionView 上的可重用性问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/22678841/

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